replace trimesh.triangulate_polygon with faster direct meshpy implementation

src/c3nav/mapdata/render/engines/opengl.py

@@ -1,14 +1,15 @@
 import io
 from collections import deque
+from functools import lru_cache
 from itertools import chain
 from typing import Optional, Union
 
+import meshpy.triangle as triangle
 import ModernGL
 import numpy as np
 from PIL import Image
 from shapely.geometry import CAP_STYLE, JOIN_STYLE, MultiPolygon, Polygon
 from shapely.ops import unary_union
-from trimesh.creation import triangulate_polygon
 
 from c3nav.mapdata.render.engines.base import FillAttribs, RenderEngine, StrokeAttribs
 from c3nav.mapdata.utils.geometry import assert_multipolygon
@@ -54,11 +55,42 @@ class OpenGLEngine(RenderEngine):
         self.np_scale = np.array((scale_x, -scale_y))
         self.np_offset = np.array((-self.minx * scale_x - 1, self.maxy * scale_y - 1))
 
+    @staticmethod
+    @lru_cache()
+    def get_face_indizes(start, length):
+        indices = np.tile(np.arange(start, start + length).reshape((-1, 1)), 2).flatten()[1:-1].reshape((length-1, 2))
+        return np.vstack((indices, (indices[-1][-1], indices[0][0])))
+
+    @staticmethod
+    def triangulate_polygon(polygon):
+        vertices = deque()
+        faces = deque()
+
+        offset = 0
+        for ring in chain((polygon.exterior, ), polygon.interiors):
+            new_vertices = np.array(ring.coords)[:-1]
+            vertices.append(new_vertices)
+            faces.append(OpenGLEngine.get_face_indizes(offset, len(new_vertices)))
+            offset += len(new_vertices)
+
+        holes = np.array(tuple(
+            Polygon(ring).representative_point().coords for ring in polygon.interiors
+        ))
+
+        info = triangle.MeshInfo()
+        info.set_points(np.vstack(vertices))
+        info.set_facets(np.vstack(faces).tolist())
+        if holes.size:
+            info.set_holes(holes.reshape((holes.shape[0], -1)))
+
+        mesh = triangle.build(info)
+        return np.array(mesh.points), np.array(mesh.elements)
+
     def _create_geometry(self, geometry: Union[Polygon, MultiPolygon], append=None):
         triangles = deque()
 
         for i, polygon in enumerate(assert_multipolygon(geometry)):
-            vertices, faces = triangulate_polygon(polygon)
+            vertices, faces = self.triangulate_polygon(polygon)
             triangles.append(vertices[faces.flatten()])
 
         vertices = np.vstack(triangles).astype(np.float32)