107 lines
3.4 KiB
Python
107 lines
3.4 KiB
Python
# Copyright (c) 2022-2024, Manfred Moitzi
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# License: MIT License
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from __future__ import annotations
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from typing import Iterable, Iterator, Sequence
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import ezdxf
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from ezdxf.math import Vec2, UVec, Vec3, safe_normal_vector, OCS
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from ._mapbox_earcut import earcut
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if ezdxf.options.use_c_ext:
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try:
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from ezdxf.acc.mapbox_earcut import earcut # type: ignore
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except ImportError:
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pass
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__all__ = [
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"mapbox_earcut_2d",
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"mapbox_earcut_3d",
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]
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def mapbox_earcut_2d(
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exterior: Iterable[UVec], holes: Iterable[Iterable[UVec]] | None = None
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) -> list[Sequence[Vec2]]:
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"""Mapbox triangulation algorithm with hole support for 2D polygons.
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Implements a modified ear slicing algorithm, optimized by z-order
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curve hashing and extended to handle holes, twisted polygons, degeneracies
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and self-intersections in a way that doesn't guarantee correctness of
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triangulation, but attempts to always produce acceptable results for
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practical data.
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Source: https://github.com/mapbox/earcut
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Args:
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exterior: exterior polygon as iterable of :class:`Vec2` objects
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holes: iterable of holes as iterable of :class:`Vec2` objects, a hole
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with single point represents a `Steiner point`_.
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Returns:
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yields the result as 3-tuples of :class:`Vec2` objects
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.. _Steiner point: https://en.wikipedia.org/wiki/Steiner_point_(computational_geometry)
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"""
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points = Vec2.list(exterior)
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if len(points) == 0:
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return []
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holes_: list[list[Vec2]] = []
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if holes:
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holes_ = [Vec2.list(hole) for hole in holes]
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return earcut(points, holes_)
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def mapbox_earcut_3d(
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exterior: Iterable[UVec], holes: Iterable[Iterable[UVec]] | None = None
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) -> Iterator[Sequence[Vec3]]:
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"""Mapbox triangulation algorithm with hole support for flat 3D polygons.
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Implements a modified ear slicing algorithm, optimized by z-order
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curve hashing and extended to handle holes, twisted polygons, degeneracies
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and self-intersections in a way that doesn't guarantee correctness of
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triangulation, but attempts to always produce acceptable results for
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practical data.
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Source: https://github.com/mapbox/earcut
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Args:
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exterior: exterior polygon as iterable of :class:`Vec3` objects
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holes: iterable of holes as iterable of :class:`Vec3` objects, a hole
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with single point represents a `Steiner point`_.
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Returns:
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yields the result as 3-tuples of :class:`Vec3` objects
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Raise:
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TypeError: invalid input data type
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ZeroDivisionError: normal vector calculation failed
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"""
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polygon = Vec3.list(exterior)
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if len(polygon) == 0:
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return
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if polygon[0].isclose(polygon[-1]):
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polygon.pop()
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count = len(polygon)
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if count < 3:
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return
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if count == 3:
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yield polygon[0], polygon[1], polygon[2]
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return
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ocs = OCS(safe_normal_vector(polygon))
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elevation = ocs.from_wcs(polygon[0]).z
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exterior_ocs = list(ocs.points_from_wcs(polygon))
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holes_ocs: list[list[Vec3]] = []
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if holes:
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holes_ocs = [list(ocs.points_from_wcs(hole)) for hole in holes]
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# Vec3 supports the _Point protocol in _mapbox_earcut.py
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# required attributes: x, y
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for triangle in earcut(exterior_ocs, holes_ocs):
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yield tuple(
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ocs.points_to_wcs(Vec3(v.x, v.y, elevation) for v in triangle)
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)
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