[Bf-blender-cvs] [84c537e6852] master: Document that tessellate_polygon() doesn't handle degenerate geometry

[Sybren A. Stüvel]

Commit: 84c537e68528177ef982479f5884af07cec322b9
Author: Sybren A. Stüvel
Date:   Mon Jan 27 16:42:25 2020 +0100
Branches: master
https://developer.blender.org/rB84c537e68528177ef982479f5884af07cec322b9

Document that tessellate_polygon() doesn't handle degenerate geometry

This 'fixes' T68554: 'API mathutils.geometry.tessellate_polygon returns
bad results sometimes' by documenting the limitations of the current
implementation.

I've also added a unit test for the function, so that any change in this
behaviour will get noticed.

No functional changes.

===================================================================

M	source/blender/python/mathutils/mathutils_geometry.c
M	tests/python/bl_pyapi_mathutils.py

===================================================================

diff --git a/source/blender/python/mathutils/mathutils_geometry.c b/source/blender/python/mathutils/mathutils_geometry.c
index fcb6a77bf36..859ece61ace 100644
--- a/source/blender/python/mathutils/mathutils_geometry.c
+++ b/source/blender/python/mathutils/mathutils_geometry.c
@@ -1246,7 +1246,8 @@ PyDoc_STRVAR(M_Geometry_tessellate_polygon_doc,
              ".. function:: tessellate_polygon(veclist_list)\n"
              "\n"
              "   Takes a list of polylines (each point a pair or triplet of numbers) and returns "
-             "the point indices for a polyline filled with triangles.\n"
+             "the point indices for a polyline filled with triangles. Does not handle degenerate "
+             "geometry (such as zero-length lines due to consecutive identical points).\n"
              "\n"
              "   :arg veclist_list: list of polylines\n"
              "   :rtype: list\n");
diff --git a/tests/python/bl_pyapi_mathutils.py b/tests/python/bl_pyapi_mathutils.py
index 5aa95f9a5f7..9dfc6c159cc 100644
--- a/tests/python/bl_pyapi_mathutils.py
+++ b/tests/python/bl_pyapi_mathutils.py
@@ -3,7 +3,7 @@
 # ./blender.bin --background -noaudio --python tests/python/bl_pyapi_mathutils.py -- --verbose
 import unittest
 from mathutils import Matrix, Vector, Quaternion
-from mathutils import kdtree
+from mathutils import kdtree, geometry
 import math
 
 # keep globals immutable
@@ -488,6 +488,43 @@ class KDTreeTesting(unittest.TestCase):
             k.find((0,) * 3, filter=lambda i: None)
 
 
+class TesselatePolygon(unittest.TestCase):
+    def test_empty(self):
+        self.assertEqual([], geometry.tessellate_polygon([]))
+
+    def test_2d(self):
+        polyline = [
+            Vector((-0.14401324093341827, 0.1266411542892456)),
+            Vector((-0.14401324093341827, 0.13)),
+            Vector((0.13532273471355438, 0.1266411542892456)),
+            Vector((0.13532273471355438, 0.13)),
+        ]
+        expect = [(0, 1, 2), (0, 3, 2)]
+        self.assertEqual(expect, geometry.tessellate_polygon([polyline]))
+
+    def test_3d(self):
+        polyline = [
+            Vector((-0.14401324093341827, 0.1266411542892456, -0.13966798782348633)),
+            Vector((-0.14401324093341827, 0.1266411542892456, 0.13966798782348633)),
+            Vector((0.13532273471355438, 0.1266411542892456, 0.13966798782348633)),
+            Vector((0.13532273471355438, 0.1266411542892456, -0.13966798782348633)),
+        ]
+        expect = [(2, 3, 0), (2, 0, 1)]
+        self.assertEqual(expect, geometry.tessellate_polygon([polyline]))
+
+    def test_3d_degenerate(self):
+        polyline = [
+            Vector((-0.14401324093341827, -0.15269476175308228, -0.13966798782348633)),
+            Vector((0.13532273471355438, -0.15269476175308228, -0.13966798782348633)),
+            Vector((0.13532273471355438, -0.15269476175308228, -0.13966798782348633)),
+            Vector((-0.14401324093341827, -0.15269476175308228, -0.13966798782348633)),
+        ]
+        # If this returns a proper result, rather than [(0, 0, 0)], it could mean that
+        # degenerate geometry is handled properly.
+        expect = [(0, 0, 0)]
+        self.assertEqual(expect, geometry.tessellate_polygon([polyline]))
+
+
 if __name__ == '__main__':
     import sys
     sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])