Polygon vertices cleanup and more robust corner containtment check

Author: weiliangjin2021

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Bug in `CoaxialLumpedPort` where source injection is off when the `normal_axis` is not `z`.
 - Validation of `freqs` in the `ComponentModeler` and `TerminalComponentModeler`.
 - Calculation of voltage and current in the `WavePort`, when one type of path integral is supplied and the transmission line mode is lossy.
+- Polygon vertices cleanup in `ClipOperation.intersections_plane`.
 
 ## [2.9.0] - 2025-08-04
 

tests/test_components/test_geometry.py

@@ -1288,8 +1288,7 @@ def test_cleanup_shapely_object():
     # Test using a non-empty exterior polygon (big_square_5x5)
     orig_polygon = shapely.Polygon(exterior_coords, interior_coords_list)
     new_polygon = cleanup_shapely_object(orig_polygon, tolerance_ratio=1e-12)
-    # Delete any nearby or overlapping vertices (cleanup_shapely_object() does not do this).
-    new_polygon = shapely.simplify(new_polygon, tolerance=1e-10)
+    # Delete any nearby or overlapping vertices (cleanup_shapely_object() now does this).
     # Now `new_polygon` should only contain the coordinates of the square (with a duplicate at end).
     assert len(new_polygon.exterior.coords) == 5  # squares have 4 vertices but shapely adds 1
     assert len(new_polygon.interiors) == 1  # only the "triangle_empty_tails" interior hole survives
@@ -1298,5 +1297,4 @@ def test_cleanup_shapely_object():
     exterior_coords = triangle_collinear  # has zero area
     orig_polygon = shapely.Polygon(exterior_coords)
     new_polygon = cleanup_shapely_object(orig_polygon, tolerance_ratio=1e-12)
-    new_polygon = shapely.simplify(new_polygon, tolerance=1e-10)
     assert len(new_polygon.exterior.coords) == 0  # empty / collinear polygons should get deleted

tidy3d/components/geometry/base.py

@@ -66,6 +66,7 @@
 
 POLY_GRID_SIZE = 1e-12
 POLY_TOLERANCE_RATIO = 1e-12
+POLY_DISTANCE_TOLERANCE = 8e-12
 
 
 _shapely_operations = {
@@ -3397,6 +3398,9 @@ def cleanup_shapely_object(obj: Shapely, tolerance_ratio: float = POLY_TOLERANCE
         cap_style="square",
         quad_segs=3,
     )
+    # Clean vertices of very close distances created during the erosion/dilation process.
+    # The distance value is heuristic.
+    cleaned_obj = cleaned_obj.simplify(POLY_DISTANCE_TOLERANCE, preserve_topology=True)
     # Revert to the original scale and position.
     rescaled_clean_obj = shapely.affinity.affine_transform(
         cleaned_obj,

tidy3d/components/grid/grid_spec.py

@@ -10,6 +10,7 @@
 
 from tidy3d.components.base import Tidy3dBaseModel, cached_property, skip_if_fields_missing
 from tidy3d.components.geometry.base import Box, ClipOperation
+from tidy3d.components.geometry.utils_2d import increment_float
 from tidy3d.components.lumped_element import LumpedElementType
 from tidy3d.components.source.utils import SourceType
 from tidy3d.components.structure import MeshOverrideStructure, Structure, StructureType
@@ -1323,6 +1324,13 @@ def _is_inplane_bounded(self) -> bool:
             self.size[(self.axis + 2) % 3]
         )
 
+    @cached_property
+    def _slightly_enlarged_box(self) -> Box:
+        """Slightly enlarged box for robust point containment querying."""
+        # increase size slightly
+        size = [increment_float(orig_length, 1) for orig_length in self.size]
+        return Box(center=self.center, size=size)
+
     def _unpop_axis(self, ax_coord: float, plane_coord: Any) -> CoordinateOptional:
         """Combine coordinate along axis with identical coordinates on the plane tangential to the axis.
 
@@ -1411,7 +1419,7 @@ def _inplane_inside(self, point: ArrayFloat2D) -> bool:
         point_3d = self.unpop_axis(
             ax_coord=self.center[self.axis], plane_coords=point, axis=self.axis
         )
-        return self.inside(point_3d[0], point_3d[1], point_3d[2])
+        return self._slightly_enlarged_box.inside(point_3d[0], point_3d[1], point_3d[2])
 
     def _corners_and_convexity_2d(
         self, structure_list: list[Structure], ravel: bool