up

README.md

@@ -33,7 +33,7 @@ NodeSlicer is a high-performance Blender extension that provides a custom node-b
 4. **Process**:
     *   Add perimeters with **Buffer Shells**.
     *   Add internal structure with the **Infill** node.
-    *   Combine or modify paths using **Join Paths** or **Boolean Paths**.
+    *   Combine or modify paths using **Path Operations**.
 5. **Generate**: Convert paths to G-code using **Paths to Gcode**.
 6. **Export & Preview**: Use **Gcode To File** to save the result, and **Gcode to Preview Mesh** to visualize the final toolpaths in the viewport.
 

core/geometry.py

@@ -28,25 +28,28 @@ def euler_rotation_matrix(rx: float, ry: float, rz: float) -> np.ndarray:
 
 from collections import OrderedDict
 
+def _make_hashable(val: Any) -> Any:
+    if isinstance(val, np.ndarray):
+        return crc32_array(val)
+    elif isinstance(val, (list, tuple)):
+        if not val:
+            return ()
+        if isinstance(val[0], np.ndarray):
+            return crc32_list(list(val))
+        return tuple(_make_hashable(v) for v in val)
+    elif isinstance(val, dict):
+        return tuple(sorted((k, _make_hashable(v)) for k, v in val.items()))
+    elif isinstance(val, set):
+        return tuple(sorted(_make_hashable(v) for v in val))
+    return val
+
 def ndarray_lru_cache(maxsize: int = 128) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
     def decorator(func: Callable[..., Any]) -> Callable[..., Any]:
         cache: OrderedDict[tuple[Any, ...], Any] = OrderedDict()
         def wrapper(*args, **kwargs):
-            key_parts = []
-            for arg in args:
-                if isinstance(arg, np.ndarray):
-                    key_parts.append(crc32_array(arg))
-                elif isinstance(arg, list) and arg and isinstance(arg[0], np.ndarray):
-                    key_parts.append(crc32_list(arg))
-                else:
-                    key_parts.append(arg)
+            key_parts = [_make_hashable(arg) for arg in args]
             for k, v in sorted(kwargs.items()):
-                if isinstance(v, np.ndarray):
-                    key_parts.append((k, crc32_array(v)))
-                elif isinstance(v, list) and v and isinstance(v[0], np.ndarray):
-                    key_parts.append((k, crc32_list(v)))
-                else:
-                    key_parts.append((k, v))
+                key_parts.append((k, _make_hashable(v)))
             
             key = tuple(key_parts)
             if key in cache:

core/nodeslicer/nodes/mesh.py

@@ -41,12 +41,19 @@ class SLICENODE_JoinMesh(SliceNodeJoiner):
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection:
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
-        merged_coll = resolve_input(self.inputs[0]) or SlicingCollection([],'')
+        first_coll = resolve_input(self.inputs[0]) if self.inputs else None
+        merged_coll = SlicingCollection([], first_coll.name if first_coll else '')
+        if first_coll:
+            merged_coll.objects = list(first_coll.objects)
+            merged_coll.transforms = [dict(t) for t in getattr(first_coll, "transforms", [])]
         
         for input in self.inputs[1:]:
             coll = resolve_input(input)
             if coll: 
-                merged_coll.objects += coll.objects
+                merged_coll.objects += list(coll.objects)
+                for t in getattr(coll, "transforms", []):
+                    if t not in merged_coll.transforms:
+                        merged_coll.transforms.append(dict(t))
 
         return merged_coll
 
@@ -63,10 +70,15 @@ class SLICENODE_JoinMeshGroups(SliceNodeJoiner):
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
         group: SlicingGroup = SlicingGroup([])
         
-        for input in self.inputs:
-            coll = resolve_input(input)
-            if coll: 
-                group.collections[coll.objects[0].name] = coll
+        for idx, input_socket in enumerate(self.inputs):
+            coll = resolve_input(input_socket)
+            if coll:
+                col_name = getattr(coll, "name", "")
+                if not col_name and coll.objects:
+                    col_name = coll.objects[0].name
+                if not col_name:
+                    col_name = f"collection_{idx}"
+                group.collections[col_name] = coll
 
         return group
 

core/nodeslicer/nodes/path.py

@@ -64,19 +64,18 @@ class SLICENODE_SliceShells(SliceNode):
     def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
         if socket_name != "Paths": return SlicePaths()
 
-        coll: SlicingCollection | SlicingGroup | None = self.resolve("Mesh")
-        layer_height: float = self.resolve("Layer Height") or 0.2
+        coll: Any = self.resolve("Mesh")
+        layer_height: float = float(self.resolve("Layer Height") or 0.2)
+        if layer_height <= 0:
+            layer_height = 0.2
+
         fl_height: float | None = None
-        if hasattr(self, "inputs") and "First Layer Height" in self.inputs:
-            try:
-                fl_height = self.resolve("First Layer Height")
-            except Exception:
-                fl_height = None
-        else:
-            try:
-                fl_height = self.resolve("First Layer Height")
-            except Exception:
-                fl_height = None
+        try:
+            fl_val = self.resolve("First Layer Height")
+            if fl_val is not None:
+                fl_height = float(fl_val)
+        except Exception:
+            fl_height = None
         if fl_height is not None and fl_height <= 0:
             fl_height = None
 
@@ -93,15 +92,31 @@ class SLICENODE_SliceShells(SliceNode):
 
         if not coll: return SlicePaths()
 
-        # Handle SlicingGroup flattening
+        # Handle SlicingGroup, SlicingCollection, SlicingObject, or list
         if isinstance(coll, SlicingGroup):
             objects = []
             for c in coll.collections.values():
                 objects.extend(c.objects)
+        elif isinstance(coll, SlicingCollection):
+            objects = list(coll.objects)
+        elif isinstance(coll, SlicingObject):
+            objects = [coll]
+        elif isinstance(coll, list):
+            objects = []
+            for item in coll:
+                if isinstance(item, SlicingGroup):
+                    for c in item.collections.values():
+                        objects.extend(c.objects)
+                elif isinstance(item, SlicingCollection):
+                    objects.extend(item.objects)
+                elif isinstance(item, SlicingObject):
+                    objects.append(item)
         else:
-            objects = coll.objects
+            objects = getattr(coll, "objects", [coll] if hasattr(coll, "mesh") else [])
 
         merged_object = SlicingObject.merge(objects)
+        if merged_object.mesh is None or merged_object.mesh.size == 0:
+            return SlicePaths()
 
         if rotation and any(rotation):
             from mathutils import Euler
@@ -110,8 +125,8 @@ class SLICENODE_SliceShells(SliceNode):
             merged_object.mesh[:, 3:4, :] = merged_object.mesh[:, 3:4, :] @ mat.T
 
         min_z = float(merged_object.mesh[:, 0:3, 2:3].min())
-        from math import floor
-        min_z = floor(min_z / layer_height) * layer_height
+        if abs(min_z) < 1e-6:
+            min_z = 0.0
         max_z = float(merged_object.mesh[:, 0:3, 2:3].max())
 
         h_first = fl_height if fl_height is not None else layer_height
@@ -124,21 +139,37 @@ class SLICENODE_SliceShells(SliceNode):
         z_first_um = min_z_um + flh_um
         z_rest_start_um = z_first_um + lh_um
 
-        if z_rest_start_um < max_z_um and lh_um > 0:
-            z_um_values = list(range(z_rest_start_um, max_z_um, lh_um))
-            z_values = np.array([z_first_um] + z_um_values, dtype=np.float64) / 1000.0
-        elif z_first_um < max_z_um:
-            z_values = np.array([z_first_um], dtype=np.float64) / 1000.0
+        if z_first_um <= max_z_um:
+            if z_rest_start_um <= max_z_um and lh_um > 0:
+                z_um_values = list(range(z_rest_start_um, max_z_um + 1, lh_um))
+                z_values = np.array([z_first_um] + z_um_values, dtype=np.float64) / 1000.0
+            else:
+                z_values = np.array([z_first_um], dtype=np.float64) / 1000.0
         else:
-            z_values = np.array([])
+            z_values = np.array([], dtype=np.float64)
 
         slices_group: list[list[np.ndarray]] | None = slice_at_range(
             [merged_object.mesh],
             z_values,
             ignore_holes=ignore_holes
         )
-        assert slices_group
-        slices = SlicePaths(slices_group[0])
+        if not slices_group or not slices_group[0]:
+            return SlicePaths()
+
+        paths = slices_group[0]
+        # Assign layer-consistent group indices based on Z height in integer microns
+        z_to_group: dict[int, int] = {}
+        groups = []
+        for p in paths:
+            if len(p) > 0:
+                z_k = int(round(p[0, 2] * 1000))
+                if z_k not in z_to_group:
+                    z_to_group[z_k] = len(z_to_group)
+                groups.append(z_to_group[z_k])
+            else:
+                groups.append(0)
+
+        slices = SlicePaths(paths, groups=groups)
         slices.layer_height = layer_height
         if fl_height is not None:
             slices.first_layer_height = fl_height
@@ -427,26 +458,6 @@ class SLICENODE_Infill(SliceNode):
             layer_rotation=rotation
         )
 
-@register_class
-class SLICENODE_GetInfillMask(SliceNode):
-    bl_label = "Get Infill Mask"
-
-    def init(self, context):
-        self.add_input("SLICESOCK_Paths")
-        self.add_output("SLICESOCK_Paths")
-
-    def draw_buttons(self, context, layout):
-        pass
-
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
-        if socket_name != "Paths": return SlicePaths()
-
-        paths: SlicePaths = self.resolve("Paths")
-
-        if not paths: return SlicePaths()
-
-        return paths.get_infill_mask()
-
 @register_class
 class SLICENODE_OverhangMask(SliceNode):
     bl_label = "Overhang Mask"
@@ -470,19 +481,23 @@ class SLICENODE_OverhangMask(SliceNode):
         return paths.get_overhang_mask(tolerance=tolerance)
 
 @register_class
-class SLICENODE_JoinSlices(SliceNodeJoiner):
-    bl_label = "Boolean Paths"
+class SLICENODE_PathOperations(SliceNodeJoiner):
+    bl_label = "Path Operations"
     socket_type = "SLICESOCK_Paths"
 
     operation: str = NfEnumProperty(
         name="Operation",
         items=[
-            ('UNION', "Union", "Union of the slices"),
-            ('INTERSECTION', "Intersection", "Intersection of the slices"),
-            ('DIFFERENCE', "Subtract", "Clipping of the first slice"),
-            ('XOR', "Exclusive or", "Exclusive or of the slices"),
+            ('ZIP', "Zip paths", "Interleave paths from all inputs layer by layer"),
+            ('EXTEND', "Extend paths", "Append paths sequentially"),
+            ('MAX_COVERAGE', "Maximum coverage", "Union of all paths"),
+            ('MIN_COVERAGE', "Minimum coverage", "Intersection of paths per layer (single paths preserved)"),
+            ('INTERSECTION', "Intersection", "Intersection of all paths"),
+            ('SUBTRACT', "Subtract", "Subtract subsequent paths from first input"),
+            ('XOR', "Exclusive or", "Exclusive or of all paths"),
         ],
-        default='UNION'
+        default='ZIP',
+        update=notify_tree_changed
     )
 
     connect_along_boundary: bool = NfBoolProperty(
@@ -494,63 +509,26 @@ class SLICENODE_JoinSlices(SliceNodeJoiner):
     def draw_buttons(self, context, layout):
         assert layout
         layout.prop(self, "operation", text="")
-        if self.operation in ['INTERSECTION', 'DIFFERENCE']:
+        if self.operation in ['MIN_COVERAGE', 'INTERSECTION', 'SUBTRACT']:
             layout.prop(self, "connect_along_boundary")
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
-        accumulated: SlicePaths = SlicePaths()
-        current: SlicePaths | None = SlicePaths()
-        for input in self.inputs:
-            current = resolve_input(input)
 
-            if not current:
-                continue
-
-            if not accumulated:
-                accumulated = current
-                continue
-
-            accumulated = accumulated.boolean(current, self.operation, connect_along_boundary=self.connect_along_boundary)
-
-        return accumulated
-
-@register_class
-class SLICENODE_JoinPaths(SliceNodeJoiner):
-    bl_label = "Join Paths"
-    socket_type = "SLICESOCK_Paths"
-
-    mode: str = NfEnumProperty(
-        name="Mode",
-        items=[
-            ('EXTEND', "Extend", "Append paths sequentially"),
-            ('ZIP', "Zip", "Interleave paths from all inputs"),
-        ],
-        default='EXTEND'
-    )
-
-    def draw_buttons(self, context, layout):
-        assert layout
-        layout.prop(self, "mode", text="")
-
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
-        from ....infra.blender.blender_slice_nodes_generic import resolve_input
-        
         inputs_data: list[SlicePaths] = []
-        for input in self.inputs:
-            paths: SlicePaths | None = resolve_input(input)
-            if paths:
+        for input_socket in self.inputs:
+            paths: SlicePaths | None = resolve_input(input_socket)
+            if paths is not None:
                 inputs_data.append(paths)
 
         if not inputs_data:
             return SlicePaths()
 
-        if self.mode == 'EXTEND':
-            return SlicePaths.extend_paths(inputs_data)
-        elif self.mode == 'ZIP':
-            return SlicePaths.zip_paths(inputs_data)
-
-        return SlicePaths()
+        return SlicePaths.path_operations(
+            inputs_data,
+            operation=self.operation,
+            connect_along_boundary=self.connect_along_boundary
+        )
 
 
 @register_class

core/nodeslicer/tree.py

@@ -505,7 +505,6 @@ class SLICENODE_MT_Geometry(Menu):
         layout.operator("node.add_node", text="Get Paths").type = "SLICENODE_GetPaths"
         layout.separator()
         layout.operator("node.add_node", text="Slice Shells").type = "SLICENODE_SliceShells"
-        layout.operator("node.add_node", text="CUDA Slice Mesh").type = "SLICENODE_CudaSliceMesh"
         layout.operator("node.add_node", text="Buffer Shells").type = "SLICENODE_BufferShells"
         layout.operator("node.add_node", text="Buffer Shells Multiple").type = "SLICENODE_BufferShellsMultiple"
         layout.operator("node.add_node", text="Buffer Curve").type = "SLICENODE_BufferCurve"
@@ -514,9 +513,8 @@ class SLICENODE_MT_Geometry(Menu):
         layout.operator("node.add_node", text="Rotate Path").type = "SLICENODE_RotatePath"
         layout.operator("node.add_node", text="Simplify Paths").type = "SLICENODE_SimplifyPaths"
         layout.operator("node.add_node", text="Infill").type = "SLICENODE_Infill"
-        layout.operator("node.add_node", text="Get Infill Mask").type = "SLICENODE_GetInfillMask"
         layout.operator("node.add_node", text="Overhang Mask").type = "SLICENODE_OverhangMask"
-        layout.operator("node.add_node", text="Boolean Paths").type = "SLICENODE_JoinSlices"
+        layout.operator("node.add_node", text="Path Operations").type = "SLICENODE_PathOperations"
         layout.separator()
         layout.operator("node.add_node", text="Math").type = "SLICENODE_FloatMath"
         layout.operator("node.add_node", text="Integer Math").type = "SLICENODE_IntMath"
@@ -559,7 +557,7 @@ class SLICENODE_MT_Joiners(Menu):
         assert layout
         layout.operator("node.add_node", text="Join Mesh Parts").type = "SLICENODE_JoinMesh"
         layout.operator("node.add_node", text="Join Mesh Groups").type = "SLICENODE_JoinMeshGroups"
-        layout.operator("node.add_node", text="Join Paths").type = "SLICENODE_JoinPaths"
+        layout.operator("node.add_node", text="Path Operations").type = "SLICENODE_PathOperations"
         layout.operator("node.add_node", text="Join Gcode").type = "SLICENODE_JoinGcode"
         layout.operator("node.add_node", text="Join Settings").type = "SLICENODE_JoinSettings"
         layout.operator("node.add_node", text="Join Execution").type = "SLICENODE_JoinExecution"

core/slice.py

@@ -5,8 +5,7 @@ import numpy as np
 import pyclipper
 from typing import Any, Literal, cast
 import copy
-from shapely.geometry.base import BaseGeometry
-from shapely.geometry import Polygon, MultiPolygon, LineString, LinearRing, MultiLineString, GeometryCollection
+from shapely.geometry import Polygon, MultiPolygon, LineString, LinearRing, MultiLineString, GeometryCollection, Point
 
 from ..infra.blender.blender_mesh_capture import PdfProperties
 
@@ -226,11 +225,23 @@ class SlicePaths(list[np.ndarray]):
 
     def offset(self, offset_vec: np.ndarray) -> SlicePaths:
         """Returns a new SlicePaths object shifted by the given vector."""
-        return self.copy_with([p + offset_vec for p in self])
+        res = self.copy_with([p + offset_vec for p in self])
+        res.transforms = [dict(t) for t in getattr(self, "transforms", [])]
+        res.transforms.append({
+            "type": "offset",
+            "offset": offset_vec.tolist() if isinstance(offset_vec, np.ndarray) else list(offset_vec)
+        })
+        return res
 
     def transform(self, matrix: np.ndarray) -> SlicePaths:
         """Applies a transformation matrix to all paths."""
-        return self.copy_with([p @ matrix.T for p in self])
+        res = self.copy_with([p @ matrix.T for p in self])
+        res.transforms = [dict(t) for t in getattr(self, "transforms", [])]
+        res.transforms.append({
+            "type": "transform",
+            "matrix": matrix.tolist() if isinstance(matrix, np.ndarray) else list(matrix)
+        })
+        return res
 
     def buffer(self, distance: float, miter: str = 'round', rotation: Any = None) -> SlicePaths:
         """Buffers (offsets) the paths. Handles optional rotation for non-planar buffering."""
@@ -443,7 +454,14 @@ class SlicePaths(list[np.ndarray]):
             new_p = (p - center) @ rot_mat.T + center
             new_paths.append(new_p)
             
-        return self.copy_with(new_paths)
+        res = self.copy_with(new_paths)
+        res.transforms = [dict(t) for t in getattr(self, "transforms", [])]
+        res.transforms.append({
+            "type": "rotate",
+            "angle_deg": float(angle_deg),
+            "center": center.tolist() if isinstance(center, np.ndarray) else list(center)
+        })
+        return res
 
     def get_first_layer_midpoint(self) -> np.ndarray:
         if not self:
@@ -468,6 +486,36 @@ class SlicePaths(list[np.ndarray]):
     def boolean(self, other: SlicePaths, operation: str = 'UNION', connect_along_boundary: bool = False) -> SlicePaths:
         return boolean_slice(self, other, operation, connect_along_boundary=connect_along_boundary)
 
+    @classmethod
+    def path_operations(cls, paths_list: list[SlicePaths], operation: str = 'ZIP', connect_along_boundary: bool = False) -> SlicePaths:
+        """Executes Path Operations across multiple SlicePaths inputs."""
+        return path_operations_slice(paths_list, operation=operation, connect_along_boundary=connect_along_boundary)
+
+    @classmethod
+    def minimum_coverage(cls, paths_list: list[SlicePaths], connect_along_boundary: bool = False) -> SlicePaths:
+        """Computes Minimum Coverage across multiple SlicePaths inputs."""
+        return minimum_coverage_slice(paths_list, connect_along_boundary=connect_along_boundary)
+
+    @classmethod
+    def maximum_coverage(cls, paths_list: list[SlicePaths], connect_along_boundary: bool = False) -> SlicePaths:
+        """Computes Maximum Coverage across multiple SlicePaths inputs."""
+        return maximum_coverage_slice(paths_list, connect_along_boundary=connect_along_boundary)
+
+    @classmethod
+    def intersection(cls, paths_list: list[SlicePaths], connect_along_boundary: bool = False) -> SlicePaths:
+        """Computes Intersection across multiple SlicePaths inputs."""
+        return intersection_slice(paths_list, connect_along_boundary=connect_along_boundary)
+
+    @classmethod
+    def subtract(cls, paths_list: list[SlicePaths], connect_along_boundary: bool = False) -> SlicePaths:
+        """Computes Difference (Subtract) across multiple SlicePaths inputs."""
+        return subtract_slice(paths_list, connect_along_boundary=connect_along_boundary)
+
+    @classmethod
+    def xor(cls, paths_list: list[SlicePaths], connect_along_boundary: bool = False) -> SlicePaths:
+        """Computes Exclusive Or (XOR) across multiple SlicePaths inputs."""
+        return xor_slice(paths_list, connect_along_boundary=connect_along_boundary)
+
     def extend_with_groups(self, other: SlicePaths | list[np.ndarray]):
         if isinstance(other, SlicePaths):
             self.extend(other)
@@ -884,6 +932,78 @@ def get_boundary_path(pt1: np.ndarray, pt2: np.ndarray, loops: list[np.ndarray])
                 
     return best_path
 
+def _group_closed_paths_into_shapes(closed_paths: list[np.ndarray]) -> list[list[np.ndarray]]:
+    """
+    Groups a list of closed paths on a layer into distinct polygon shapes,
+    where each shape consists of one outer boundary and zero or more inner holes.
+    Uses topological containment with representative points:
+    - Paths contained in an even number of enclosing paths (0, 2, ...) are Outer boundaries.
+    - Paths contained in an odd number of enclosing paths (1, 3, ...) are Holes belonging
+      to the immediately enclosing Outer boundary.
+    """
+    if not closed_paths:
+        return []
+    if len(closed_paths) == 1:
+        return [[closed_paths[0]]]
+
+    polys: list[tuple[int, np.ndarray, Polygon, float]] = []
+    for i, p in enumerate(closed_paths):
+        pts = p[:, :2]
+        if len(pts) < 3:
+            continue
+        try:
+            poly = Polygon(pts)
+            if not poly.is_valid:
+                poly = poly.buffer(0)
+            if not poly.is_empty:
+                polys.append((i, p, poly, float(poly.area)))
+        except Exception:
+            continue
+
+    if not polys:
+        return [[p] for p in closed_paths]
+    if len(polys) == 1:
+        return [[polys[0][1]]]
+
+    # Sort descending by area so enclosing paths come before enclosed ones
+    polys.sort(key=lambda x: x[3], reverse=True)
+
+    # For each polygon, find all strictly larger polygons that contain its representative point
+    shapes_map: dict[int, list[np.ndarray]] = {}
+    outer_entries: list[tuple[int, Polygon, float]] = []
+
+    for idx, p, poly, area in polys:
+        rep_pt = poly.representative_point()
+        # Find all larger polygons containing this representative point
+        containers = [
+            (c_idx, c_poly, c_area)
+            for (c_idx, c_p, c_poly, c_area) in polys
+            if c_area > area and (c_poly.contains(rep_pt) or c_poly.buffer(1e-5).contains(rep_pt))
+        ]
+
+        if len(containers) % 2 == 0:
+            # Even enclosing count -> Outer boundary
+            shapes_map[idx] = [p]
+            outer_entries.append((idx, poly, area))
+        else:
+            # Odd enclosing count -> Hole belonging to the smallest enclosing outer
+            # Find the enclosing outer with the smallest area
+            enclosing_outers = [
+                (o_idx, o_poly, o_area)
+                for (o_idx, o_poly, o_area) in outer_entries
+                if o_area > area and (o_poly.contains(rep_pt) or o_poly.buffer(1e-5).contains(rep_pt))
+            ]
+            if enclosing_outers:
+                # Smallest area is the last one because outer_entries is in descending order
+                parent_idx = enclosing_outers[-1][0]
+                shapes_map[parent_idx].append(p)
+            elif outer_entries:
+                shapes_map[outer_entries[-1][0]].append(p)
+            else:
+                shapes_map[idx] = [p]
+
+    return list(shapes_map.values())
+
 @ndarray_lru_cache(maxsize=128)
 def boolean_slice(subject: SlicePaths, object: SlicePaths, operation: str = 'UNION', connect_along_boundary: bool = False) -> SlicePaths:
     all_z_keys: set[int] = set()
@@ -891,11 +1011,15 @@ def boolean_slice(subject: SlicePaths, object: SlicePaths, operation: str = 'UNI
     object_dict: dict[int, list[np.ndarray]] = {}
 
     for s in subject:
+        if len(s) < 2:
+            continue
         z = int(round(s[0, 2] * SCALE))
         all_z_keys.add(z)
         subject_dict.setdefault(z, []).append(s)
 
     for s in object:
+        if len(s) < 2:
+            continue
         z = int(round(s[0, 2] * SCALE))
         all_z_keys.add(z)
         object_dict.setdefault(z, []).append(s)
@@ -911,60 +1035,53 @@ def boolean_slice(subject: SlicePaths, object: SlicePaths, operation: str = 'UNI
             if object_slices and operation == 'UNION':
                 results.extend(object_slices)
                 results.groups.extend([group] * len(object_slices))
+                group += 1
             continue
 
         if not object_slices:
             if operation != 'INTERSECTION':
                 results.extend(subject_slices)
                 results.groups.extend([group] * len(subject_slices))
+                group += 1
             continue
 
         z = subject_slices[0][0, 2]
 
         pc = pyclipper.Pyclipper() # pyright: ignore[reportAttributeAccessIssue]
 
-        # Function to process and add paths to Clipper
-        def add_paths_to_clipper(paths, role):
-            for s in paths:
-                path_pts = s[:, :2]
-                is_closed = is_closed_path(s)
-                if is_closed:
-                    path_pts = path_pts[:-1]
-                scaled = (path_pts * SCALE).round().astype(np.int64).tolist()
-                pc.AddPath(scaled, role, is_closed) # pyright: ignore[reportAttributeAccessIssue]
-
         layer_results = []
 
-        def process_op(subs, clips_scaled, clips_pts, op_type):
-            for s in subs:
+        sub_closed = [s for s in subject_slices if is_closed_path(s)]
+        sub_open = [s for s in subject_slices if not is_closed_path(s)]
+        obj_closed = [s for s in object_slices if is_closed_path(s)]
+        obj_open = [s for s in object_slices if not is_closed_path(s)]
+
+        sub_closed_scaled = [(s[:, :2][:-1] * SCALE).round().astype(np.int64).tolist() for s in sub_closed]
+        sub_closed_pts = [s[:, :2] for s in sub_closed]
+        obj_closed_scaled = [(s[:, :2][:-1] * SCALE).round().astype(np.int64).tolist() for s in obj_closed]
+        obj_closed_pts = [s[:, :2] for s in obj_closed]
+
+        def process_open_op(open_paths, clips_scaled, clips_pts, op_type):
+            for s in open_paths:
                 path_pts = s[:, :2]
-                is_closed = is_closed_path(s)
-                
-                if not connect_along_boundary or is_closed:
-                    pc.Clear()
-                    if is_closed: path_pts = path_pts[:-1]
-                    pc.AddPath((path_pts * SCALE).round().astype(np.int64).tolist(), pyclipper.PT_SUBJECT, is_closed)  # pyright: ignore[reportAttributeAccessIssue]
+                pc.Clear()
+                if not connect_along_boundary:
+                    pc.AddPath((path_pts * SCALE).round().astype(np.int64).tolist(), pyclipper.PT_SUBJECT, False)
                     for c in clips_scaled:
-                        pc.AddPath(c, pyclipper.PT_CLIP, True) # pyright: ignore[reportAttributeAccessIssue]
-                    
-                    solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD) # pyright: ignore[reportAttributeAccessIssue]
-                    for path in pyclipper.ClosedPathsFromPolyTree(solution): # pyright: ignore[reportAttributeAccessIssue]
-                        fpath = np.array(path, dtype=np.float64) / SCALE
-                        fpath_3d = np.column_stack([fpath, np.full(len(fpath), z)])
-                        layer_results.append(np.vstack([fpath_3d, fpath_3d[0]]))
-                    for path in pyclipper.OpenPathsFromPolyTree(solution): # pyright: ignore[reportAttributeAccessIssue]
+                        pc.AddPath(c, pyclipper.PT_CLIP, True)
+                    solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD)
+                    for path in pyclipper.OpenPathsFromPolyTree(solution):
                         fpath = np.array(path, dtype=np.float64) / SCALE
                         layer_results.append(np.column_stack([fpath, np.full(len(fpath), z)]))
                 else:
-                    pc.Clear()
-                    pc.AddPath((path_pts * SCALE).round().astype(np.int64).tolist(), pyclipper.PT_SUBJECT, False) # pyright: ignore[reportAttributeAccessIssue]
+                    pc.AddPath((path_pts * SCALE).round().astype(np.int64).tolist(), pyclipper.PT_SUBJECT, False)
                     for c in clips_scaled:
-                        pc.AddPath(c, pyclipper.PT_CLIP, True) # pyright: ignore[reportAttributeAccessIssue]
-                    
-                    solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD) # pyright: ignore[reportAttributeAccessIssue]
-                    open_results = pyclipper.OpenPathsFromPolyTree(solution) # pyright: ignore[reportAttributeAccessIssue]
-                    if not open_results: continue
-                    
+                        pc.AddPath(c, pyclipper.PT_CLIP, True)
+                    solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD)
+                    open_results = pyclipper.OpenPathsFromPolyTree(solution)
+                    if not open_results:
+                        continue
+
                     def get_p(pt):
                         p1 = path_pts[:-1]
                         p2 = path_pts[1:]
@@ -988,81 +1105,105 @@ def boolean_slice(subject: SlicePaths, object: SlicePaths, operation: str = 'UNI
                             fpath = fpath[::-1]
                             p_start, p_end = p_end, p_start
                         segments.append((p_start, fpath))
-                    
+
                     segments.sort(key=lambda x: x[0])
-                    
                     current_group = [segments[0][1]]
                     for i in range(1, len(segments)):
                         prev_end = current_group[-1][-1] * SCALE
                         curr_start = segments[i][1][0] * SCALE
                         scaled_loops = [(pts * SCALE) for pts in clips_pts]
                         b_path = get_boundary_path(prev_end, curr_start, scaled_loops)
-                        
+
                         if b_path is not None:
                             if len(b_path) > 2:
                                 current_group.append(b_path[1:-1] / SCALE)
                             current_group.append(segments[i][1])
                         else:
-                            # Path is not continuous along boundary, finalize current group
                             path_to_add = np.vstack(current_group)
                             layer_results.append(np.column_stack([path_to_add, np.full(len(path_to_add), z)]))
                             current_group = [segments[i][1]]
-                    
+
                     path_to_add = np.vstack(current_group)
                     layer_results.append(np.column_stack([path_to_add, np.full(len(path_to_add), z)]))
 
         if operation == 'INTERSECTION':
-            obj_closed_pts = [s[:, :2] for s in object_slices if is_closed_path(s)]
-            obj_closed_scaled = [(pts[:-1] * SCALE).round().astype(np.int64).tolist() for pts in obj_closed_pts]
-            process_op(subject_slices, obj_closed_scaled, obj_closed_pts, pyclipper.CT_INTERSECTION) # pyright: ignore[reportAttributeAccessIssue]
-            
-            # Pass 2 for B_open ∩ A_closed
-            b_open = [s for s in object_slices if not is_closed_path(s)]
-            if b_open:
-                sub_closed_pts = [s[:, :2] for s in subject_slices if is_closed_path(s)]
-                sub_closed_scaled = [(pts[:-1] * SCALE).round().astype(np.int64).tolist() for pts in sub_closed_pts]
-                process_op(b_open, sub_closed_scaled, sub_closed_pts, pyclipper.CT_INTERSECTION) # pyright: ignore[reportAttributeAccessIssue]
-        
+            if sub_closed and obj_closed:
+                pc.Clear()
+                for c in sub_closed_scaled:
+                    pc.AddPath(c, pyclipper.PT_SUBJECT, True)
+                for c in obj_closed_scaled:
+                    pc.AddPath(c, pyclipper.PT_CLIP, True)
+                solution = pc.Execute2(pyclipper.CT_INTERSECTION, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD)
+                for path in pyclipper.ClosedPathsFromPolyTree(solution):
+                    fpath = np.array(path, dtype=np.float64) / SCALE
+                    fpath_3d = np.column_stack([fpath, np.full(len(fpath), z)])
+                    fpath_3d = np.vstack([fpath_3d, fpath_3d[0]])
+                    layer_results.append(align_path_seam_sharpest(fpath_3d))
+                for path in pyclipper.OpenPathsFromPolyTree(solution):
+                    fpath = np.array(path, dtype=np.float64) / SCALE
+                    layer_results.append(np.column_stack([fpath, np.full(len(fpath), z)]))
+
+            if sub_open and obj_closed_scaled:
+                process_open_op(sub_open, obj_closed_scaled, obj_closed_pts, pyclipper.CT_INTERSECTION)
+            if obj_open and sub_closed_scaled:
+                process_open_op(obj_open, sub_closed_scaled, sub_closed_pts, pyclipper.CT_INTERSECTION)
+
         elif operation == 'DIFFERENCE':
-            obj_closed_pts = [s[:, :2] for s in object_slices if is_closed_path(s)]
-            obj_closed_scaled = [(pts[:-1] * SCALE).round().astype(np.int64).tolist() for pts in obj_closed_pts]
-            process_op(subject_slices, obj_closed_scaled, obj_closed_pts, pyclipper.CT_DIFFERENCE) # pyright: ignore[reportAttributeAccessIssue]
-            # DIFFERENCE is not symmetric for open paths in the same way, usually A - B means A is the main focus.
+            if sub_closed and obj_closed:
+                pc.Clear()
+                for c in sub_closed_scaled:
+                    pc.AddPath(c, pyclipper.PT_SUBJECT, True)
+                for c in obj_closed_scaled:
+                    pc.AddPath(c, pyclipper.PT_CLIP, True)
+                solution = pc.Execute2(pyclipper.CT_DIFFERENCE, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD)
+                for path in pyclipper.ClosedPathsFromPolyTree(solution):
+                    fpath = np.array(path, dtype=np.float64) / SCALE
+                    fpath_3d = np.column_stack([fpath, np.full(len(fpath), z)])
+                    fpath_3d = np.vstack([fpath_3d, fpath_3d[0]])
+                    layer_results.append(align_path_seam_sharpest(fpath_3d))
+                for path in pyclipper.OpenPathsFromPolyTree(solution):
+                    fpath = np.array(path, dtype=np.float64) / SCALE
+                    layer_results.append(np.column_stack([fpath, np.full(len(fpath), z)]))
+            elif sub_closed and not obj_closed:
+                layer_results.extend(sub_closed)
+
+            if sub_open and obj_closed_scaled:
+                process_open_op(sub_open, obj_closed_scaled, obj_closed_pts, pyclipper.CT_DIFFERENCE)
+            elif sub_open and not obj_closed:
+                layer_results.extend(sub_open)
 
         else:
             # UNION, XOR
-            add_paths_to_clipper(subject_slices, pyclipper.PT_SUBJECT) # pyright: ignore[reportAttributeAccessIssue]
-            obj_closed = []
-            obj_open = []
-            for s in object_slices:
-                if is_closed_path(s): obj_closed.append(s)
-                else: obj_open.append(s)
-
-            if operation in ['UNION', 'XOR']:
-                add_paths_to_clipper(obj_open, pyclipper.PT_SUBJECT) # pyright: ignore[reportAttributeAccessIssue]
-            
-            for s in obj_closed:
+            pc.Clear()
+            for c in sub_closed_scaled:
+                pc.AddPath(c, pyclipper.PT_SUBJECT, True)
+            for s in sub_open:
                 path_pts = s[:, :2]
-                scaled = (path_pts[:-1] * SCALE).round().astype(np.int64).tolist()
-                pc.AddPath(scaled, pyclipper.PT_CLIP, True) # pyright: ignore[reportAttributeAccessIssue]
-            
-            op_type = pyclipper.CT_UNION # pyright: ignore[reportAttributeAccessIssue]
-            if operation == 'UNION': op_type = pyclipper.CT_UNION # pyright: ignore[reportAttributeAccessIssue]
-            elif operation == 'XOR': op_type = pyclipper.CT_XOR # pyright: ignore[reportAttributeAccessIssue]
+                scaled = (path_pts * SCALE).round().astype(np.int64).tolist()
+                pc.AddPath(scaled, pyclipper.PT_SUBJECT, False)
 
-            solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD) # pyright: ignore[reportAttributeAccessIssue]
-            for path in pyclipper.ClosedPathsFromPolyTree(solution): # pyright: ignore[reportAttributeAccessIssue]
-                fpath = np.array(path) / SCALE
+            for c in obj_closed_scaled:
+                pc.AddPath(c, pyclipper.PT_CLIP, True)
+            for s in obj_open:
+                path_pts = s[:, :2]
+                scaled = (path_pts * SCALE).round().astype(np.int64).tolist()
+                pc.AddPath(scaled, pyclipper.PT_SUBJECT, False)
+
+            op_type = pyclipper.CT_UNION if operation == 'UNION' else pyclipper.CT_XOR
+            solution = pc.Execute2(op_type, pyclipper.PFT_EVENODD, pyclipper.PFT_EVENODD)
+            for path in pyclipper.ClosedPathsFromPolyTree(solution):
+                fpath = np.array(path, dtype=np.float64) / SCALE
                 fpath_3d = np.column_stack([fpath, np.full(len(fpath), z)])
-                layer_results.append(np.vstack([fpath_3d, fpath_3d[0]]))
-            for path in pyclipper.OpenPathsFromPolyTree(solution): # pyright: ignore[reportAttributeAccessIssue]
-                fpath = np.array(path) / SCALE
+                fpath_3d = np.vstack([fpath_3d, fpath_3d[0]])
+                layer_results.append(align_path_seam_sharpest(fpath_3d))
+            for path in pyclipper.OpenPathsFromPolyTree(solution):
+                fpath = np.array(path, dtype=np.float64) / SCALE
                 layer_results.append(np.column_stack([fpath, np.full(len(fpath), z)]))
 
         results.extend(layer_results)
         results.groups.extend([group] * len(layer_results))
         group += 1
-            
+
     # Transfer per-group/path metadata (extrusion_rate, feedrate, extra_attributes) from subject
     calc_ext, calc_feed, calc_extra = _transfer_group_attributes(subject, results, results.groups)
     results.extrusion_rate = calc_ext
@@ -1070,15 +1211,360 @@ def boolean_slice(subject: SlicePaths, object: SlicePaths, operation: str = 'UNI
     results.extra_attributes = calc_extra
 
     for attr, val in subject.__dict__.items():
-        if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes"]:
-            setattr(results, attr, val)
+        if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes", "transforms", "objects_info", "name"]:
+            setattr(results, attr, copy.deepcopy(val) if isinstance(val, (list, dict)) else val)
     for attr, val in object.__dict__.items():
-        if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes"]:
-            if not hasattr(results, attr):
-                setattr(results, attr, val)
+        if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes", "transforms", "objects_info", "name"]:
+            if not hasattr(results, attr) or getattr(results, attr) is None or getattr(results, attr) == "" or getattr(results, attr) == []:
+                setattr(results, attr, copy.deepcopy(val) if isinstance(val, (list, dict)) else val)
+
+    merged_transforms = []
+    merged_names = []
+    merged_objs = []
+    for sp in [subject, object]:
+        obj_info = getattr(sp, "objects_info", None)
+        if obj_info:
+            for obj_entry in obj_info.get("objects", []):
+                if obj_entry not in merged_objs:
+                    merged_objs.append(dict(obj_entry))
+                    n_str = obj_entry.get("name", "")
+                    if n_str and n_str not in merged_names:
+                        merged_names.append(n_str)
+        elif hasattr(sp, "name") and getattr(sp, "name"):
+            n_str = str(getattr(sp, "name"))
+            if n_str and n_str not in merged_names:
+                merged_names.append(n_str)
+                merged_objs.append({"name": n_str, "polygon": []})
+
+        for t in getattr(sp, "transforms", []):
+            if t not in merged_transforms:
+                merged_transforms.append(dict(t))
+
+    results.transforms = merged_transforms
+    if merged_objs:
+        results.objects_info = {"objects": merged_objs}
+        results.name = "-".join(merged_names)
 
     return results
 
+def minimum_coverage_slice(
+    paths_list: list[SlicePaths],
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """
+    Computes the Minimum Coverage across multiple SlicePaths inputs (or within a single SlicePaths input).
+    For each layer (grouped by integer micron Z), it calculates the intersection of all
+    paths in that layer. If only one path (or single shape with holes) exists on a layer,
+    it preserves that path/shape intact.
+    """
+    if not paths_list:
+        return SlicePaths()
+
+    primary = next((sp for sp in paths_list if len(sp) > 0), paths_list[0])
+    if not any(len(sp) > 0 for sp in paths_list):
+        return SlicePaths()
+
+    all_z_keys: set[int] = set()
+    input_layer_maps: list[dict[int, list[np.ndarray]]] = []
+
+    for sp in paths_list:
+        layer_map: dict[int, list[np.ndarray]] = {}
+        for p in sp:
+            if len(p) < 2:
+                continue
+            z_key = int(round(p[0, 2] * SCALE))
+            all_z_keys.add(z_key)
+            layer_map.setdefault(z_key, []).append(p)
+        input_layer_maps.append(layer_map)
+
+    results = SlicePaths()
+    group = 0
+
+    for z_key in sorted(all_z_keys):
+        active_indices = [
+            i for i, lmap in enumerate(input_layer_maps) if z_key in lmap and len(lmap[z_key]) > 0
+        ]
+
+        if not active_indices:
+            continue
+
+        if len(active_indices) == 1:
+            idx = active_indices[0]
+            layer_paths = input_layer_maps[idx][z_key]
+            if len(layer_paths) <= 1:
+                results.extend(layer_paths)
+                results.groups.extend([group] * len(layer_paths))
+                group += 1
+            else:
+                closed_paths = [p for p in layer_paths if is_closed_path(p)]
+                open_paths = [p for p in layer_paths if not is_closed_path(p)]
+
+                shapes = _group_closed_paths_into_shapes(closed_paths)
+                if len(shapes) <= 1:
+                    # Single shape with holes + open paths -> preserve intact
+                    results.extend(layer_paths)
+                    results.groups.extend([group] * len(layer_paths))
+                    group += 1
+                else:
+                    # Multiple distinct shapes on the same layer -> compute their intersection
+                    curr_sp = paths_list[idx].copy_with(shapes[0])
+                    for s in shapes[1:]:
+                        curr_sp = boolean_slice(
+                            curr_sp,
+                            paths_list[idx].copy_with(s),
+                            operation='INTERSECTION',
+                            connect_along_boundary=connect_along_boundary
+                        )
+                        if not curr_sp:
+                            break
+                    if open_paths and curr_sp:
+                        for op in open_paths:
+                            curr_sp = boolean_slice(
+                                paths_list[idx].copy_with([op]),
+                                curr_sp,
+                                operation='INTERSECTION',
+                                connect_along_boundary=connect_along_boundary
+                            )
+                    if curr_sp:
+                        results.extend(curr_sp)
+                        results.groups.extend([group] * len(curr_sp))
+                        group += 1
+            continue
+
+        # Multiple active inputs on this layer -> intersect across inputs
+        idx0 = active_indices[0]
+        curr_sp = paths_list[idx0].copy_with(input_layer_maps[idx0][z_key])
+
+        for next_idx in active_indices[1:]:
+            next_sp = paths_list[next_idx].copy_with(input_layer_maps[next_idx][z_key])
+            curr_sp = boolean_slice(
+                curr_sp,
+                next_sp,
+                operation='INTERSECTION',
+                connect_along_boundary=connect_along_boundary
+            )
+            if not curr_sp:
+                break
+
+        if curr_sp:
+            results.extend(curr_sp)
+            results.groups.extend([group] * len(curr_sp))
+            group += 1
+
+    calc_ext, calc_feed, calc_extra = _transfer_group_attributes(primary, results, results.groups)
+    results.extrusion_rate = calc_ext
+    results.feedrate = calc_feed
+    results.extra_attributes = calc_extra
+
+    for attr, val in primary.__dict__.items():
+        if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes", "transforms", "objects_info", "name"]:
+            setattr(results, attr, copy.deepcopy(val) if isinstance(val, (list, dict)) else val)
+
+    merged_transforms = []
+    merged_names = []
+    merged_objs = []
+    for sp in paths_list:
+        obj_info = getattr(sp, "objects_info", None)
+        if obj_info:
+            for obj_entry in obj_info.get("objects", []):
+                if obj_entry not in merged_objs:
+                    merged_objs.append(dict(obj_entry))
+                    n_str = obj_entry.get("name", "")
+                    if n_str and n_str not in merged_names:
+                        merged_names.append(n_str)
+        elif hasattr(sp, "name") and getattr(sp, "name"):
+            n_str = str(getattr(sp, "name"))
+            if n_str and n_str not in merged_names:
+                merged_names.append(n_str)
+                merged_objs.append({"name": n_str, "polygon": []})
+
+        for t in getattr(sp, "transforms", []):
+            if t not in merged_transforms:
+                merged_transforms.append(dict(t))
+
+    results.transforms = merged_transforms
+    if merged_objs:
+        results.objects_info = {"objects": merged_objs}
+        results.name = "-".join(merged_names)
+
+    return results
+
+def maximum_coverage_slice(
+    paths_list: list[SlicePaths],
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """
+    Computes the Maximum Coverage (Union) across multiple SlicePaths inputs (or within a single SlicePaths input).
+    For each layer (grouped by integer micron Z), it calculates the union of all paths.
+    """
+    if not paths_list:
+        return SlicePaths()
+
+    primary = next((sp for sp in paths_list if len(sp) > 0), paths_list[0])
+    non_empty = [sp for sp in paths_list if len(sp) > 0]
+    if not non_empty:
+        return SlicePaths()
+
+    if len(non_empty) == 1:
+        sp = non_empty[0]
+        layer_map: dict[int, list[np.ndarray]] = {}
+        for p in sp:
+            if len(p) < 2:
+                continue
+            z_key = int(round(p[0, 2] * SCALE))
+            layer_map.setdefault(z_key, []).append(p)
+
+        results = SlicePaths()
+        group = 0
+        for z_key in sorted(layer_map.keys()):
+            l_paths = layer_map[z_key]
+            if len(l_paths) <= 1:
+                results.extend(l_paths)
+                results.groups.extend([group] * len(l_paths))
+                group += 1
+            else:
+                closed_paths = [p for p in l_paths if is_closed_path(p)]
+                open_paths = [p for p in l_paths if not is_closed_path(p)]
+
+                shapes = _group_closed_paths_into_shapes(closed_paths)
+                if len(shapes) <= 1:
+                    results.extend(l_paths)
+                    results.groups.extend([group] * len(l_paths))
+                    group += 1
+                else:
+                    curr_sp = sp.copy_with(shapes[0])
+                    for s in shapes[1:]:
+                        curr_sp = boolean_slice(
+                            curr_sp,
+                            sp.copy_with(s),
+                            operation='UNION',
+                            connect_along_boundary=connect_along_boundary
+                        )
+                    if open_paths:
+                        curr_sp.extend(open_paths)
+                        curr_sp.groups.extend([group] * len(open_paths))
+                    if curr_sp:
+                        results.extend(curr_sp)
+                        results.groups.extend([group] * len(curr_sp))
+                        group += 1
+
+        calc_ext, calc_feed, calc_extra = _transfer_group_attributes(sp, results, results.groups)
+        results.extrusion_rate = calc_ext
+        results.feedrate = calc_feed
+        results.extra_attributes = calc_extra
+        for attr, val in sp.__dict__.items():
+            if attr not in ["groups", "extrusion_rate", "feedrate", "extra_attributes", "transforms", "objects_info", "name"]:
+                setattr(results, attr, copy.deepcopy(val) if isinstance(val, (list, dict)) else val)
+
+        merged_transforms = []
+        for t in getattr(sp, "transforms", []):
+            if t not in merged_transforms:
+                merged_transforms.append(dict(t))
+        results.transforms = merged_transforms
+
+        return results
+
+    accumulated = non_empty[0]
+    for sp in non_empty[1:]:
+        accumulated = boolean_slice(
+            accumulated,
+            sp,
+            operation='UNION',
+            connect_along_boundary=connect_along_boundary
+        )
+    return accumulated
+
+def intersection_slice(
+    paths_list: list[SlicePaths],
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """Computes the Intersection across multiple SlicePaths inputs (same behavior as Boolean Paths)."""
+    if not paths_list:
+        return SlicePaths()
+    if len(paths_list) == 1:
+        return paths_list[0]
+
+    accumulated = paths_list[0]
+    for sp in paths_list[1:]:
+        if not accumulated:
+            return SlicePaths()
+        accumulated = boolean_slice(
+            accumulated,
+            sp,
+            operation='INTERSECTION',
+            connect_along_boundary=connect_along_boundary
+        )
+    return accumulated
+
+def subtract_slice(
+    paths_list: list[SlicePaths],
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """Computes the Difference (Subtract) of subsequent SlicePaths inputs from the first input."""
+    if not paths_list:
+        return SlicePaths()
+    if len(paths_list) == 1:
+        return paths_list[0]
+
+    accumulated = paths_list[0]
+    for sp in paths_list[1:]:
+        if not accumulated:
+            return SlicePaths()
+        accumulated = boolean_slice(
+            accumulated,
+            sp,
+            operation='DIFFERENCE',
+            connect_along_boundary=connect_along_boundary
+        )
+    return accumulated
+
+def xor_slice(
+    paths_list: list[SlicePaths],
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """Computes the Symmetric Difference (XOR) across multiple SlicePaths inputs."""
+    if not paths_list:
+        return SlicePaths()
+    if len(paths_list) == 1:
+        return paths_list[0]
+
+    accumulated = paths_list[0]
+    for sp in paths_list[1:]:
+        accumulated = boolean_slice(
+            accumulated,
+            sp,
+            operation='XOR',
+            connect_along_boundary=connect_along_boundary
+        )
+    return accumulated
+
+def path_operations_slice(
+    paths_list: list[SlicePaths],
+    operation: str = 'ZIP',
+    connect_along_boundary: bool = False
+) -> SlicePaths:
+    """Dispatches Path Operations across multiple SlicePaths inputs."""
+    if not paths_list:
+        return SlicePaths()
+
+    op = str(operation).upper()
+    if op in ('ZIP', 'ZIP_PATHS'):
+        return SlicePaths.zip_paths(paths_list)
+    elif op in ('EXTEND', 'EXTEND_PATHS'):
+        return SlicePaths.extend_paths(paths_list)
+    elif op in ('MAX_COVERAGE', 'MAXIMUM_COVERAGE', 'UNION'):
+        return maximum_coverage_slice(paths_list, connect_along_boundary=connect_along_boundary)
+    elif op in ('MIN_COVERAGE', 'MINIMUM_COVERAGE'):
+        return minimum_coverage_slice(paths_list, connect_along_boundary=connect_along_boundary)
+    elif op in ('INTERSECTION', 'INTERSECT'):
+        return intersection_slice(paths_list, connect_along_boundary=connect_along_boundary)
+    elif op in ('SUBTRACT', 'DIFFERENCE'):
+        return subtract_slice(paths_list, connect_along_boundary=connect_along_boundary)
+    elif op == 'XOR':
+        return xor_slice(paths_list, connect_along_boundary=connect_along_boundary)
+    else:
+        return SlicePaths.zip_paths(paths_list)
+
 def geometry_to_paths(geom: Any, z: float) -> list[np.ndarray]:
     """Helper to convert shapely geometries to a list of 3D numpy arrays with a given Z height."""
     paths = []
@@ -1629,6 +2115,9 @@ class Pather(object):
         self.objects_info: dict[str, Any] | None = getattr(paths, "objects_info", None)
         self.name: str = str(getattr(paths, "name", ""))
 
+        for k, v in kwargs.items():
+            setattr(self, k, v)
+
     @property
     def layer_width(self) -> float:
         if self._layer_width is not None:

doc/MODULES.md

@@ -35,7 +35,10 @@ This file provides a mapping of modules to their primary responsibilities and ke
     - `link_segments()`: Logic for joining loose segments into continuous paths.
     - `buffer_slice()`: Offset utility using PyclipperOffset. Supports rotated offsetting.
     - `infill_slice()`: Generates rotated grid or rectilinear infill patterns, ensuring layer-to-layer consistency.
-    - `boolean_slice()`: Performs 2D boolean operations (Union, Intersection, etc.) on slice sets.
+    - `boolean_slice()`: Performs 2D boolean operations (Union, Intersection, Subtract, XOR) on slice sets with hole support.
+    - `path_operations_slice()`: Unified dispatcher for multi-input path operations (`ZIP`, `EXTEND`, `MAX_COVERAGE`, `MIN_COVERAGE`, `SUBTRACT`, `XOR`).
+    - `minimum_coverage_slice()`: Computes layer-by-layer intersection across multiple inputs while preserving single-path/input layers.
+    - `maximum_coverage_slice()`: Computes layer-by-layer union across multiple inputs.
 
 - `geometry.py`:
     - Geometry utility functions.

doc/NODES.md

@@ -104,9 +104,17 @@ All nodes are found in the **Add (Shift+A)** menu under the **SliceNodes** categ
     - **Density**: Distance between lines in units.
     - **Infill Rotation**: Base rotation of the infill pattern.
     - **Layer Rotation**: Rotation of the entire slice to align infill with specific planes.
-- **Get Infill Mask**: Computes the solid 2D infill mask for each layer, resolving exterior boundaries and interior holes into closed boundary loops.
 - **Overhang Mask**: Computes the accumulated overhang mask for each layer, propagating support requirements from top to bottom.
-- **Boolean Paths**: Performs 2D boolean operations (`UNION`, `INTERSECTION`, `DIFFERENCE`, `XOR`) on multiple slice sets.
+- **Path Operations**: Multi-input joiner node performing composite geometric, boolean, and interleaving operations on `SlicePaths`.
+    - **Operations**:
+        - **Zip paths**: Interleaves paths from all inputs layer by layer.
+        - **Extend paths**: Appends paths sequentially.
+        - **Maximum coverage**: Computes the union of all input paths across each layer.
+        - **Minimum coverage**: Computes the intersection of all input paths per layer, preserving single-path/input layers.
+        - **Intersection**: Computes the standard boolean intersection of all input paths across each layer.
+        - **Subtract**: Subtracts subsequent inputs from the first input.
+        - **Exclusive or**: Computes symmetric difference across all inputs.
+    - **Connect along boundary**: Boolean option to connect clipped open segments along the boundary of the clipping polygon.
 - **Math**: Float math operations.
 - **Integer Math**: Simple integer operations (Add, Multiply, etc.).
 
@@ -151,8 +159,9 @@ All nodes are found in the **Add (Shift+A)** menu under the **SliceNodes** categ
 - **Load Gcode**: Reads a G-code file from disk.
 
 ### Utility & Joiners
-- **Join Mesh**: Merges multiple `SlicingObject` instances into one.
-- **Join Paths**: Combines multiple `SlicePaths`. Supports Sequential or Interleaved modes.
+- **Join Mesh Parts**: Merges multiple `SlicingObject` instances into one `SlicingCollection`.
+- **Join Mesh Groups**: Combines multiple `SlicingCollection` instances into a `SlicingGroup`.
+- **Path Operations**: Multi-input joiner performing Zip, Extend, Maximum coverage, Minimum coverage, Intersection, Subtract, and XOR operations.
 - **Join Gcode**: Concatenates multiple G-code strings.
 - **Join Settings**: Sequentially merges multiple override dictionaries. Later inputs overwrite earlier ones for matching keys.
 - **Join Execution**: Synchronizes sequential execution flows.

infra/blender/blender_mesh_capture.py

@@ -550,11 +550,10 @@ def _cached_objects_to_tris(obj_names: tuple[str, ...], matrices: tuple[tuple[fl
             tx_verts = homogeneous_verts @ trimesh.matrix_world
             tx_verts = (tx_verts[:, :3]) * scale
 
-            homogeneous_norm: NDArray[float64] = np.hstack((tris_v_n, np.ones((tris_v_n.shape[0], 1)))) # type: ignore
-            tx_norm = homogeneous_norm @ trimesh.matrix_world.T
-            tx_norm = tx_norm[:, :3]
-            tx_norm = tx_norm / np.linalg.norm(tx_norm, axis=1, keepdims=True)
-            tx_norm = tx_norm[:, np.newaxis, :]
+            tx_norm = tris_v_n @ trimesh.matrix_world[:3, :3]
+            norms_len = np.linalg.norm(tx_norm, axis=1, keepdims=True)
+            norms_len = np.where(norms_len == 0, 1.0, norms_len)
+            tx_norm = (tx_norm / norms_len)[:, np.newaxis, :]
 
             tx_tris = tx_verts[tris_v_i]
             

registry.py

@@ -73,7 +73,10 @@ def blender_unregister_timers():
 
 import os
 
-from bpy.utils.previews import ImagePreviewCollection
+try:
+    from bpy.utils.previews import ImagePreviewCollection
+except ImportError:
+    ImagePreviewCollection = Any  # type: ignore
 _icons_pcoll: ImagePreviewCollection | None = None
 
 def blender_register_icons():

tests/test_slice.py

@@ -1,6 +1,6 @@
 import numpy as np
 import unittest
-from unittest.mock import MagicMock
+from unittest.mock import MagicMock, patch
 import sys
 from pathlib import Path
 
@@ -210,7 +210,6 @@ class TestSlice(unittest.TestCase):
 
     def test_get_infill_mask(self):
         from NodeSlicer.core.slice import SlicePaths
-        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_GetInfillMask
 
         # Outer square: (0,0) to (10,10) at Z=3.0 (area 100)
         outer = np.array([
@@ -250,12 +249,6 @@ class TestSlice(unittest.TestCase):
         areas.sort()
         self.assertAlmostEqual(areas[0], 16.0, places=2)  # Hole area
         self.assertAlmostEqual(areas[1], 100.0, places=2) # Outer area
-        
-        # Test with node evaluation
-        node = SLICENODE_GetInfillMask()
-        node.resolve = lambda key: slice_paths if key == "Paths" else None
-        node_mask = node.evaluate_output("Paths")
-        self.assertEqual(len(node_mask), 2)
 
     def test_get_infill_mask_multiple_holes_and_islands(self):
         from NodeSlicer.core.slice import SlicePaths
@@ -586,6 +579,70 @@ class TestSlice(unittest.TestCase):
         # First layer extrusion rates should be multiplied by 0.3 / 0.2 = 1.5
         np.testing.assert_allclose(slices.extrusion_rate[0], 1.5)
 
+    def test_slice_shells_comprehensive_validation(self):
+        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_SliceShells
+        from NodeSlicer.infra.blender.blender_mesh_capture import SlicingObject, SlicingCollection, SlicingGroup
+
+        # 10x10x1.0 box mesh
+        vertices = np.array([
+            [0.0, 0.0, 0.0], [10.0, 0.0, 0.0], [10.0, 10.0, 0.0], [0.0, 10.0, 0.0],
+            [0.0, 0.0, 1.0], [10.0, 0.0, 1.0], [10.0, 10.0, 1.0], [0.0, 10.0, 1.0],
+        ])
+        faces = [
+            [0, 1, 2], [0, 2, 3],
+            [4, 6, 5], [4, 7, 6],
+            [0, 4, 5], [0, 5, 1],
+            [1, 5, 6], [1, 6, 2],
+            [2, 6, 7], [2, 7, 3],
+            [3, 7, 4], [3, 4, 0]
+        ]
+        triangles = np.zeros((len(faces), 4, 3))
+        for i, face in enumerate(faces):
+            triangles[i, 0] = vertices[face[0]]
+            triangles[i, 1] = vertices[face[1]]
+            triangles[i, 2] = vertices[face[2]]
+
+        sobj = SlicingObject()
+        sobj.name = "TestBox"
+        sobj.mesh = triangles
+
+        # 1. Direct SlicingObject input support
+        node = SLICENODE_SliceShells()
+        node.resolve = lambda name: sobj if name == "Mesh" else (0.2 if name == "Layer Height" else (0.35 if name == "First Layer Height" else None))
+        slices = node.evaluate_output("Paths")
+
+        # Layer count: with min_z=0, max_z=1.0, flh=0.35, lh=0.2:
+        # Layers: 0.35, 0.55, 0.75, 0.95 -> 4 layers
+        self.assertEqual(len(slices), 4)
+        self.assertAlmostEqual(slices[0][0, 2], 0.35)
+        self.assertAlmostEqual(slices[1][0, 2], 0.55)
+        self.assertAlmostEqual(slices[2][0, 2], 0.75)
+        self.assertAlmostEqual(slices[3][0, 2], 0.95)
+
+        # Groups must match layer index
+        self.assertEqual(slices.groups, [0, 1, 2, 3])
+
+        # Extrusion rate for first layer is 0.35 / 0.2 = 1.75
+        np.testing.assert_allclose(slices.extrusion_rate[0], 1.75)
+        np.testing.assert_allclose(slices.extrusion_rate[1], 1.0)
+        self.assertEqual(slices.layer_height, 0.2)
+        self.assertEqual(slices.first_layer_height, 0.35)
+
+        # 2. Equal first layer height (0.2 / 0.2) -> exactly 5 layers: 0.2, 0.4, 0.6, 0.8, 1.0
+        node.resolve = lambda name: sobj if name == "Mesh" else (0.2 if name == "Layer Height" else (0.2 if name == "First Layer Height" else None))
+        slices_eq = node.evaluate_output("Paths")
+        self.assertEqual(len(slices_eq), 5)
+        self.assertAlmostEqual(slices_eq[0][0, 2], 0.2)
+        self.assertAlmostEqual(slices_eq[-1][0, 2], 1.0)
+        np.testing.assert_allclose(slices_eq.extrusion_rate[0], 1.0)
+
+        # 3. First layer height <= 0 fallback to layer_height
+        node.resolve = lambda name: sobj if name == "Mesh" else (0.2 if name == "Layer Height" else (0.0 if name == "First Layer Height" else None))
+        slices_zero_fl = node.evaluate_output("Paths")
+        self.assertEqual(len(slices_zero_fl), 5)
+        self.assertAlmostEqual(slices_zero_fl[0][0, 2], 0.2)
+        self.assertIsNone(getattr(slices_zero_fl, "first_layer_height", None))
+
     def test_slicepaths_attribute_conservation(self):
         from NodeSlicer.core.slice import SlicePaths
         
@@ -928,12 +985,12 @@ class TestSlice(unittest.TestCase):
         node.ignore_holes = False
         node.resolve = lambda name: scoll if name == "Mesh" else (0.5 if name == "Layer Height" else None)
         slices_normal = node.evaluate_output("Paths")
-        self.assertEqual(len(slices_normal), 2)  # Outer + hole
+        self.assertEqual(len(slices_normal), 4)  # 2 layers * (Outer + hole) = 4
 
         # 2. Evaluation with ignore_holes=True
         node.ignore_holes = True
         slices_ignored = node.evaluate_output("Paths")
-        self.assertEqual(len(slices_ignored), 1)  # Only outer
+        self.assertEqual(len(slices_ignored), 2)  # 2 layers * (Only outer) = 2
 
         # 3. Evaluation when node lacks ignore_holes property (simulating missing property / legacy tree)
         node_missing = SLICENODE_SliceShells.__new__(SLICENODE_SliceShells)
@@ -941,7 +998,7 @@ class TestSlice(unittest.TestCase):
         node_missing.resolve = lambda name: scoll if name == "Mesh" else (0.5 if name == "Layer Height" else None)
         slices_missing = node_missing.evaluate_output("Paths")
         self.assertIsNotNone(slices_missing)
-        self.assertEqual(len(slices_missing), 2)
+        self.assertEqual(len(slices_missing), 4)
 
         # 4. draw_buttons with and without ignore_holes does not fail
         mock_layout = MagicMock()
@@ -988,7 +1045,477 @@ class TestSlice(unittest.TestCase):
         self.assertTrue(is_closed_path(paths[0]))
         self.assertTrue(np.allclose(paths[0][0], paths[0][-1]))
 
+    def test_path_operations_zip(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Input 1: layers at Z=1.0 and Z=2.0
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[0, 0, 2.0], [10, 0, 2.0], [10, 10, 2.0], [0, 10, 2.0], [0, 0, 2.0]])
+        sp1 = SlicePaths([p1, p2], groups=[0, 1])
+
+        # Input 2: layers at Z=1.0 and Z=2.0
+        q1 = np.array([[5, 5, 1.0], [15, 5, 1.0], [15, 15, 1.0], [5, 15, 1.0], [5, 5, 1.0]])
+        q2 = np.array([[5, 5, 2.0], [15, 5, 2.0], [15, 15, 2.0], [5, 15, 2.0], [5, 5, 2.0]])
+        sp2 = SlicePaths([q1, q2], groups=[0, 1])
+
+        zipped = SlicePaths.path_operations([sp1, sp2], operation='ZIP')
+        self.assertEqual(len(zipped), 4)
+        # Verify layer interleaving: (p1, q1) for group 0, (p2, q2) for group 1
+        self.assertEqual(zipped.groups, [0, 0, 1, 1])
+        self.assertTrue(np.allclose(zipped[0], p1))
+        self.assertTrue(np.allclose(zipped[1], q1))
+        self.assertTrue(np.allclose(zipped[2], p2))
+        self.assertTrue(np.allclose(zipped[3], q2))
+
+    def test_path_operations_extend(self):
+        from NodeSlicer.core.slice import SlicePaths
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[0, 0, 2.0], [10, 0, 2.0], [10, 10, 2.0], [0, 10, 2.0], [0, 0, 2.0]])
+        sp1 = SlicePaths([p1], groups=[0])
+        sp2 = SlicePaths([p2], groups=[1])
+
+        extended = SlicePaths.path_operations([sp1, sp2], operation='EXTEND')
+        self.assertEqual(len(extended), 2)
+        self.assertTrue(np.allclose(extended[0], p1))
+        self.assertTrue(np.allclose(extended[1], p2))
+
+    def test_path_operations_max_coverage(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Union of two overlapping squares at Z=1.0: (0,0)-(10,10) and (5,0)-(15,10)
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[5, 0, 1.0], [15, 0, 1.0], [15, 10, 1.0], [5, 10, 1.0], [5, 0, 1.0]])
+        sp1 = SlicePaths([p1], groups=[0])
+        sp2 = SlicePaths([p2], groups=[0])
+
+        union_res = SlicePaths.path_operations([sp1, sp2], operation='MAX_COVERAGE')
+        self.assertEqual(len(union_res), 1)
+        # Bounding box should span (0,0) to (15,10)
+        self.assertAlmostEqual(union_res[0][:, 0].min(), 0.0)
+        self.assertAlmostEqual(union_res[0][:, 0].max(), 15.0)
+
+    def test_path_operations_min_coverage_and_holes(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Input 1 has two layers:
+        # Layer 1 (Z=1.0): Donut: Outer (0,0)-(20,20) and Hole (5,5)-(15,15)
+        outer1 = np.array([[0, 0, 1.0], [20, 0, 1.0], [20, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        hole1 = np.array([[5, 5, 1.0], [15, 5, 1.0], [15, 15, 1.0], [5, 15, 1.0], [5, 5, 1.0]])
+        # Layer 2 (Z=2.0): Solid square (0,0)-(20,20)
+        square2 = np.array([[0, 0, 2.0], [20, 0, 2.0], [20, 20, 2.0], [0, 20, 2.0], [0, 0, 2.0]])
+        sp1 = SlicePaths([outer1, hole1, square2], groups=[0, 0, 1])
+
+        # Input 2 exists ONLY on Layer 1 (Z=1.0): Cutting box (-5,-5) to (10,25)
+        cutter = np.array([[-5, -5, 1.0], [10, -5, 1.0], [10, 25, 1.0], [-5, 25, 1.0], [-5, -5, 1.0]])
+        sp2 = SlicePaths([cutter], groups=[0])
+
+        min_cov = SlicePaths.path_operations([sp1, sp2], operation='MIN_COVERAGE')
+        
+        # Layer 1 (Z=1.0): Both inputs active -> intersection of donut with left cutter box -> 1 C-bracket contour
+        # Layer 2 (Z=2.0): ONLY Input 1 active -> preserves Input 1 path completely!
+        self.assertEqual(len(min_cov), 2)
+        
+        layer1_paths = [p for p in min_cov if np.allclose(p[:, 2], 1.0)]
+        layer2_paths = [p for p in min_cov if np.allclose(p[:, 2], 2.0)]
+        
+        self.assertEqual(len(layer1_paths), 1)
+        self.assertEqual(len(layer2_paths), 1)
+        # Layer 2 is exactly preserved
+        self.assertTrue(np.allclose(layer2_paths[0], square2))
+        # Layer 1 max X is 10.0 (clipped by cutter)
+        self.assertAlmostEqual(layer1_paths[0][:, 0].max(), 10.0)
+
+    def test_path_operations_subtract_and_xor(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Square at Z=1.0: (0,0)-(20,20)
+        outer = np.array([[0, 0, 1.0], [20, 0, 1.0], [20, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        # Hole cutter: (5,5)-(15,15)
+        hole_cutter = np.array([[5, 5, 1.0], [15, 5, 1.0], [15, 15, 1.0], [5, 15, 1.0], [5, 5, 1.0]])
+        sp_outer = SlicePaths([outer], groups=[0])
+        sp_cutter = SlicePaths([hole_cutter], groups=[0])
+
+        # Test Subtract (creates donut: outer + hole)
+        sub_res = SlicePaths.path_operations([sp_outer, sp_cutter], operation='SUBTRACT')
+        self.assertEqual(len(sub_res), 2)
+
+        # Test XOR
+        xor_res = SlicePaths.path_operations([sp_outer, sp_cutter], operation='XOR')
+        self.assertEqual(len(xor_res), 2)
+
+        # Test Intersection
+        inter_res = SlicePaths.path_operations([sp_outer, sp_cutter], operation='INTERSECTION')
+        self.assertEqual(len(inter_res), 1)
+        # Should match sp_cutter bounds (5 to 15)
+        self.assertAlmostEqual(inter_res[0][:, 0].min(), 5.0)
+        self.assertAlmostEqual(inter_res[0][:, 0].max(), 15.0)
+
+    def test_path_operations_intersection_vs_min_coverage(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Input 1 has layer at Z=1.0 and layer at Z=2.0
+        p1_l1 = np.array([[0, 0, 1.0], [20, 0, 1.0], [20, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        p1_l2 = np.array([[0, 0, 2.0], [20, 0, 2.0], [20, 20, 2.0], [0, 20, 2.0], [0, 0, 2.0]])
+        sp1 = SlicePaths([p1_l1, p1_l2], groups=[0, 1])
+
+        # Input 2 has ONLY layer at Z=1.0 (from X=10 to 30)
+        p2_l1 = np.array([[10, 0, 1.0], [30, 0, 1.0], [30, 20, 1.0], [10, 20, 1.0], [10, 0, 1.0]])
+        sp2 = SlicePaths([p2_l1], groups=[0])
+
+        # Intersection: Z=1.0 intersects to [10, 20], but Z=2.0 has no counterpart in sp2 so produces nothing
+        inter_res = SlicePaths.path_operations([sp1, sp2], operation='INTERSECTION')
+        self.assertEqual(len(inter_res), 1)
+        self.assertAlmostEqual(inter_res[0][0, 2], 1.0)
+        self.assertAlmostEqual(inter_res[0][:, 0].min(), 10.0)
+        self.assertAlmostEqual(inter_res[0][:, 0].max(), 20.0)
+
+        # Minimum coverage: Z=1.0 intersects to [10, 20], AND Z=2.0 is preserved because only 1 input is present
+        min_cov = SlicePaths.path_operations([sp1, sp2], operation='MIN_COVERAGE')
+        self.assertEqual(len(min_cov), 2)
+        zs = [p[0, 2] for p in min_cov]
+        self.assertIn(1.0, zs)
+        self.assertIn(2.0, zs)
+
+    def test_path_operations_node_evaluation(self):
+        from NodeSlicer.core.slice import SlicePaths
+        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_PathOperations
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[5, 0, 1.0], [15, 0, 1.0], [15, 10, 1.0], [5, 10, 1.0], [5, 0, 1.0]])
+        sp1 = SlicePaths([p1], groups=[0])
+        sp2 = SlicePaths([p2], groups=[0])
+
+        node = SLICENODE_PathOperations()
+        mock_socket1 = MagicMock()
+        mock_socket2 = MagicMock()
+        node.inputs = [mock_socket1, mock_socket2]
+
+        # Mock resolve_input to return sp1 and sp2
+        with patch("NodeSlicer.infra.blender.blender_slice_nodes_generic.resolve_input", side_effect=[sp1, sp2] * 7):
+            node.operation = 'ZIP'
+            self.assertEqual(len(node.evaluate_output("Paths")), 2)
+
+            node.operation = 'EXTEND'
+            self.assertEqual(len(node.evaluate_output("Paths")), 2)
+
+            node.operation = 'MAX_COVERAGE'
+            self.assertEqual(len(node.evaluate_output("Paths")), 1)
+
+            node.operation = 'MIN_COVERAGE'
+            self.assertEqual(len(node.evaluate_output("Paths")), 1)
+
+            node.operation = 'INTERSECTION'
+            self.assertEqual(len(node.evaluate_output("Paths")), 1)
+
+            node.operation = 'SUBTRACT'
+            self.assertEqual(len(node.evaluate_output("Paths")), 1)
+
+            node.operation = 'XOR'
+            self.assertEqual(len(node.evaluate_output("Paths")), 2)
+
+    def test_path_operations_single_input_min_coverage(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Single input with 1 path per layer (Z=1.0 and Z=2.0)
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[5, 5, 2.0], [15, 5, 2.0], [15, 15, 2.0], [5, 15, 2.0], [5, 5, 2.0]])
+        sp = SlicePaths([p1, p2], groups=[0, 1])
+
+        res = SlicePaths.path_operations([sp], operation='MIN_COVERAGE')
+        self.assertEqual(len(res), 2)
+        self.assertTrue(np.allclose(res[0], p1))
+        self.assertTrue(np.allclose(res[1], p2))
+
+        # Single input with 2 overlapping paths on Z=1.0 and 1 path on Z=2.0
+        p1_b = np.array([[5, 0, 1.0], [15, 0, 1.0], [15, 10, 1.0], [5, 10, 1.0], [5, 0, 1.0]])
+        sp_multi = SlicePaths([p1, p1_b, p2], groups=[0, 0, 1])
+        res_multi = SlicePaths.path_operations([sp_multi], operation='MIN_COVERAGE')
+        self.assertEqual(len(res_multi), 2)
+        # Z=1.0 should be intersection [5, 10] in X
+        l1 = [p for p in res_multi if np.allclose(p[:, 2], 1.0)][0]
+        self.assertAlmostEqual(l1[:, 0].min(), 5.0)
+        self.assertAlmostEqual(l1[:, 0].max(), 10.0)
+        # Z=2.0 should be preserved intact
+        l2 = [p for p in res_multi if np.allclose(p[:, 2], 2.0)][0]
+        self.assertTrue(np.allclose(l2, p2))
+
+    def test_path_operations_single_input_max_coverage(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Single input with 2 overlapping squares on Z=1.0
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        p2 = np.array([[5, 0, 1.0], [15, 0, 1.0], [15, 10, 1.0], [5, 10, 1.0], [5, 0, 1.0]])
+        sp = SlicePaths([p1, p2], groups=[0, 0])
+
+        res = SlicePaths.path_operations([sp], operation='MAX_COVERAGE')
+        self.assertEqual(len(res), 1)
+        self.assertAlmostEqual(res[0][:, 0].min(), 0.0)
+        self.assertAlmostEqual(res[0][:, 0].max(), 15.0)
+
+    def test_path_operations_single_input_donut_hole(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Donut: Outer CCW (0,0)-(20,20) and Hole CW (5,5)-(15,15)
+        outer = np.array([[0, 0, 1.0], [20, 0, 1.0], [20, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        hole = np.array([[5, 5, 1.0], [5, 15, 1.0], [15, 15, 1.0], [15, 5, 1.0], [5, 5, 1.0]])
+        sp = SlicePaths([outer, hole], groups=[0, 0])
+
+        # Min coverage on single input with hole preserves both outer and hole
+        min_res = SlicePaths.path_operations([sp], operation='MIN_COVERAGE')
+        self.assertEqual(len(min_res), 2)
+
+        # Max coverage on single input with hole preserves both outer and hole
+        max_res = SlicePaths.path_operations([sp], operation='MAX_COVERAGE')
+        self.assertEqual(len(max_res), 2)
+
+    def test_path_operations_edge_cases(self):
+        from NodeSlicer.core.slice import SlicePaths
+        # Empty inputs list
+        self.assertEqual(len(SlicePaths.path_operations([], operation='MIN_COVERAGE')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='MAX_COVERAGE')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='INTERSECTION')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='SUBTRACT')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='XOR')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='ZIP')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([], operation='EXTEND')), 0)
+
+        # List of empty SlicePaths
+        empty_sp = SlicePaths()
+        self.assertEqual(len(SlicePaths.path_operations([empty_sp], operation='MIN_COVERAGE')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([empty_sp, empty_sp], operation='MAX_COVERAGE')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([empty_sp, empty_sp], operation='INTERSECTION')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([empty_sp, empty_sp], operation='SUBTRACT')), 0)
+        self.assertEqual(len(SlicePaths.path_operations([empty_sp, empty_sp], operation='XOR')), 0)
+
+        # Non-empty with empty
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        sp1 = SlicePaths([p1], groups=[0])
+
+        # Subtract empty from sp1 should return sp1
+        sub_res = SlicePaths.path_operations([sp1, empty_sp], operation='SUBTRACT')
+        self.assertEqual(len(sub_res), 1)
+
+        # Subtract sp1 from empty should return empty
+        sub_res_empty = SlicePaths.path_operations([empty_sp, sp1], operation='SUBTRACT')
+        self.assertEqual(len(sub_res_empty), 0)
+
+        # Intersection with empty should return empty
+        inter_res = SlicePaths.path_operations([sp1, empty_sp], operation='INTERSECTION')
+        self.assertEqual(len(inter_res), 0)
+
+        # Direct classmethods on SlicePaths
+        self.assertEqual(len(SlicePaths.minimum_coverage([sp1])), 1)
+        self.assertEqual(len(SlicePaths.maximum_coverage([sp1])), 1)
+        self.assertEqual(len(SlicePaths.intersection([sp1])), 1)
+        self.assertEqual(len(SlicePaths.subtract([sp1])), 1)
+        self.assertEqual(len(SlicePaths.xor([sp1])), 1)
+
+    def test_intersection_with_holes_open_and_closed(self):
+        from NodeSlicer.core.slice import SlicePaths, boolean_slice
+
+        # Donut: Outer (0,0)-(20,20) and Hole (5,5)-(15,15)
+        outer = np.array([[0, 0, 1.0], [20, 0, 1.0], [20, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        hole = np.array([[5, 5, 1.0], [5, 15, 1.0], [15, 15, 1.0], [15, 5, 1.0], [5, 5, 1.0]])
+        donut = SlicePaths([outer, hole], groups=[0, 0])
+
+        # Test 1: Open line crossing donut
+        line = np.array([[-5, 10, 1.0], [25, 10, 1.0]])
+        line_sp = SlicePaths([line], groups=[0])
+
+        # Line as subject, donut as object
+        res_line_sub = boolean_slice(line_sp, donut, operation='INTERSECTION', connect_along_boundary=False)
+        self.assertEqual(len(res_line_sub), 2)
+        # Segments should be X: [0, 5] and [15, 20]
+        x_spans = sorted([(p[:, 0].min(), p[:, 0].max()) for p in res_line_sub], key=lambda s: s[0])
+        self.assertAlmostEqual(x_spans[0][0], 0.0, places=2)
+        self.assertAlmostEqual(x_spans[0][1], 5.0, places=2)
+        self.assertAlmostEqual(x_spans[1][0], 15.0, places=2)
+        self.assertAlmostEqual(x_spans[1][1], 20.0, places=2)
+
+        # Donut as subject, line as object (intersection is commutative for geometry)
+        res_donut_sub = boolean_slice(donut, line_sp, operation='INTERSECTION', connect_along_boundary=False)
+        self.assertEqual(len(res_donut_sub), 2)
+        x_spans2 = sorted([(p[:, 0].min(), p[:, 0].max()) for p in res_donut_sub], key=lambda s: s[0])
+        self.assertAlmostEqual(x_spans2[0][0], 0.0, places=2)
+        self.assertAlmostEqual(x_spans2[0][1], 5.0, places=2)
+        self.assertAlmostEqual(x_spans2[1][0], 15.0, places=2)
+        self.assertAlmostEqual(x_spans2[1][1], 20.0, places=2)
+
+        # Test 2: Closed square intersecting donut (cutting it into a C-shape)
+        half_square = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 20, 1.0], [0, 20, 1.0], [0, 0, 1.0]])
+        half_sp = SlicePaths([half_square], groups=[0])
+        res_c_shape = boolean_slice(donut, half_sp, operation='INTERSECTION')
+        self.assertEqual(len(res_c_shape), 1)
+
+        # Test 3: Enclosing square intersecting donut (preserving the donut and hole)
+        enclosing = np.array([[-5, -5, 1.0], [25, -5, 1.0], [25, 25, 1.0], [-5, 25, 1.0], [-5, -5, 1.0]])
+        enclosing_sp = SlicePaths([enclosing], groups=[0])
+        res_donut_kept = boolean_slice(donut, enclosing_sp, operation='INTERSECTION')
+        self.assertEqual(len(res_donut_kept), 2)
+
+        # Test 4: Path Operations INTERSECTION with donut
+        res_path_op = SlicePaths.path_operations([donut, enclosing_sp], operation='INTERSECTION')
+        self.assertEqual(len(res_path_op), 2)
+
+        # Test 5: Open line with connect_along_boundary=True
+        res_connected = boolean_slice(line_sp, donut, operation='INTERSECTION', connect_along_boundary=True)
+        self.assertEqual(len(res_connected), 1)
+
+    def test_metadata_and_transforms_preservation(self):
+        from NodeSlicer.core.slice import SlicePaths
+
+        p1 = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        sp1 = SlicePaths([p1], groups=[0], name="ObjectA")
+        sp1.transforms = [{"type": "initial", "val": 1}]
+
+        # Rotate
+        rotated = sp1.rotate(90.0, center=np.array([5.0, 5.0, 1.0]))
+        self.assertEqual(len(rotated.transforms), 2)
+        self.assertEqual(rotated.transforms[1]["type"], "rotate")
+        self.assertEqual(rotated.transforms[1]["angle_deg"], 90.0)
+        self.assertEqual(rotated.name, "ObjectA")
+
+        # Offset
+        offset_sp = rotated.offset(np.array([10.0, 0.0, 0.0]))
+        self.assertEqual(len(offset_sp.transforms), 3)
+        self.assertEqual(offset_sp.transforms[2]["type"], "offset")
+        self.assertEqual(offset_sp.transforms[2]["offset"], [10.0, 0.0, 0.0])
+
+        # Path operations (Intersection / Union / Zip / Extend) merging metadata
+        p2 = np.array([[5, 0, 1.0], [15, 0, 1.0], [15, 10, 1.0], [5, 10, 1.0], [5, 0, 1.0]])
+        sp2 = SlicePaths([p2], groups=[0], name="ObjectB")
+        sp2.transforms = [{"type": "scale", "factor": 2.0}]
+
+        merged_zip = SlicePaths.zip_paths([sp1, sp2])
+        self.assertIn("ObjectA", merged_zip.name)
+        self.assertIn("ObjectB", merged_zip.name)
+        self.assertEqual(len(merged_zip.transforms), 2)
+
+        merged_inter = SlicePaths.path_operations([sp1, sp2], operation='INTERSECTION')
+        self.assertIn("ObjectA", merged_inter.name)
+        self.assertIn("ObjectB", merged_inter.name)
+        self.assertEqual(len(merged_inter.transforms), 2)
+
+    def test_complex_donut_intersection_and_bullseye(self):
+        from NodeSlicer.core.slice import SlicePaths, _group_closed_paths_into_shapes, boolean_slice
+
+        # Bullseye target: Outer (0,0)-(30,30), Hole (5,5)-(25,25), Island (10,10)-(20,20)
+        outer = np.array([[0, 0, 1.0], [30, 0, 1.0], [30, 30, 1.0], [0, 30, 1.0], [0, 0, 1.0]])
+        hole = np.array([[5, 5, 1.0], [5, 25, 1.0], [25, 25, 1.0], [25, 5, 1.0], [5, 5, 1.0]])
+        island = np.array([[10, 10, 1.0], [20, 10, 1.0], [20, 20, 1.0], [10, 20, 1.0], [10, 10, 1.0]])
+
+        shapes = _group_closed_paths_into_shapes([outer, hole, island])
+        self.assertEqual(len(shapes), 2)
+        # Shape 1 is [outer, hole], Shape 2 is [island]
+        shapes_sorted = sorted(shapes, key=lambda s: len(s), reverse=True)
+        self.assertEqual(len(shapes_sorted[0]), 2) # Outer + Hole
+        self.assertEqual(len(shapes_sorted[1]), 1) # Island
+
+        # Intersect bullseye with a vertical slice (0..15 in X)
+        cutter = np.array([[0, -5, 1.0], [15, -5, 1.0], [15, 35, 1.0], [0, 35, 1.0], [0, -5, 1.0]])
+        bullseye_sp = SlicePaths([outer, hole, island], groups=[0, 0, 0])
+        cutter_sp = SlicePaths([cutter], groups=[0])
+
+        inter_res = boolean_slice(bullseye_sp, cutter_sp, operation='INTERSECTION')
+        self.assertGreater(len(inter_res), 0)
+        # Verify all resulting points have X <= 15.001
+        for p in inter_res:
+            self.assertLessEqual(p[:, 0].max(), 15.001)
+
+    def test_full_metadata_lifecycle(self):
+        from NodeSlicer.core.slice import SlicePaths
+
+        p = np.array([[0, 0, 1.0], [10, 0, 1.0], [10, 10, 1.0], [0, 10, 1.0], [0, 0, 1.0]])
+        sp = SlicePaths(
+            [p],
+            groups=[0],
+            extrusion_rate=[np.array([1.5, 1.5, 1.5, 1.5, 1.5])],
+            feedrate=[np.array([1200.0, 1200.0, 1200.0, 1200.0, 1200.0])],
+            extra_attributes={"fan": [np.array([100.0, 100.0, 100.0, 100.0, 100.0])]},
+            layer_height=0.25,
+            first_layer_height=0.3,
+            name="Part1",
+            objects_info={"objects": [{"name": "Part1", "polygon": []}]}
+        )
+
+        # Rotate and check metadata
+        rotated = sp.rotate(45.0)
+        self.assertEqual(rotated.layer_height, 0.25)
+        self.assertEqual(rotated.first_layer_height, 0.3)
+        self.assertEqual(rotated.name, "Part1")
+        self.assertEqual(len(rotated.transforms), 1)
+        self.assertEqual(rotated.transforms[0]["type"], "rotate")
+        self.assertAlmostEqual(rotated.transforms[0]["angle_deg"], 45.0)
+
+        # Buffer and check metadata
+        buffered = sp.buffer(1.0)
+        self.assertEqual(buffered.layer_height, 0.25)
+        self.assertEqual(buffered.first_layer_height, 0.3)
+        self.assertEqual(buffered.name, "Part1")
+
+        # Infill and check metadata
+        infilled = sp.infill(10.0, infill_type='RECTILINEAR')
+        self.assertEqual(infilled.layer_height, 0.25)
+        self.assertEqual(infilled.first_layer_height, 0.3)
+        self.assertEqual(infilled.name, "Part1")
+
+
+class TestCodeReviewBugFixes(unittest.TestCase):
+    def test_ndarray_lru_cache_empty_list_and_dict(self):
+        from NodeSlicer.core.slice import buffer_slice
+        # buffer_slice is decorated with @ndarray_lru_cache
+        res_paths, res_groups = buffer_slice([], 1.0)
+        self.assertEqual(res_paths, [])
+        self.assertEqual(res_groups, [])
+
+    def test_pather_kwargs(self):
+        from NodeSlicer.core.slice import Pather
+        path = np.array([[0, 0, 0], [10, 0, 0]], dtype=np.float64)
+        pather = Pather([path], feedrate=1500.0, retraction=1.2, bed_center_x=120.0)
+        self.assertEqual(pather.feedrate, 1500.0)
+        self.assertEqual(pather.retraction, 1.2)
+        self.assertEqual(pather.bed_center_x, 120.0)
+
+    def test_join_mesh_immutability(self):
+        from NodeSlicer.core.nodeslicer.nodes.mesh import SLICENODE_JoinMesh
+        from NodeSlicer.infra.blender.blender_mesh_capture import SlicingCollection, SlicingObject
+
+        so1 = SlicingObject()
+        so1.name = "obj1"
+        so2 = SlicingObject()
+        so2.name = "obj2"
+
+        coll1 = SlicingCollection([], "coll1")
+        coll1.objects = [so1]
+        coll2 = SlicingCollection([], "coll2")
+        coll2.objects = [so2]
+
+        node = SLICENODE_JoinMesh()
+        node.inputs = [MagicMock(), MagicMock()]
+
+        with patch("NodeSlicer.infra.blender.blender_slice_nodes_generic.resolve_input", side_effect=[coll1, coll2]):
+            res = node.evaluate_output("Mesh")
+            self.assertEqual(len(res.objects), 2)
+            # Ensure coll1.objects was NOT mutated
+            self.assertEqual(len(coll1.objects), 1)
+
+    def test_join_mesh_groups_empty_collection(self):
+        from NodeSlicer.core.nodeslicer.nodes.mesh import SLICENODE_JoinMeshGroups
+        from NodeSlicer.infra.blender.blender_mesh_capture import SlicingCollection
+
+        coll_empty = SlicingCollection([], "empty_coll")
+        node = SLICENODE_JoinMeshGroups()
+        node.inputs = [MagicMock()]
+
+        with patch("NodeSlicer.infra.blender.blender_slice_nodes_generic.resolve_input", return_value=coll_empty):
+            group = node.evaluate_output("Mesh")
+            self.assertIn("empty_coll", group.collections)
+
+    def test_slice_shells_empty_mesh(self):
+        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_SliceShells
+        from NodeSlicer.infra.blender.blender_mesh_capture import SlicingCollection
+
+        empty_coll = SlicingCollection([], "empty")
+        node = SLICENODE_SliceShells()
+        node.inputs = [MagicMock(), MagicMock()]
+
+        with patch.object(node, "resolve", side_effect=lambda name: empty_coll if name == "Mesh" else 0.2):
+            res = node.evaluate_output("Paths")
+            self.assertEqual(len(res), 0)
+
 
 if __name__ == '__main__':
     unittest.main()
 
+