Improvements to the Freestyle Python API (needed by the SVG Exporter)

This patch adds some new functionality to the Freestyle Python API, notably:

  - MaterialBP1D, checks whether the supplied arguments have the same material
  - Fixes a potential crash in CurvePoint.fedge (due to NULL pointer)
  - Makes (error handling in) boolean predicates more robust
  - Adds a BoundingBox type, to make working with bounding boxes easier
  - Adds several new functions (get_object_name, get_strokes, is_poly_clockwise, material_from_fedge)
  - Adds a StrokeCollector StrokeShader, that collects all the strokes from a specific call to Operators.create()
  - Adds hashing and rich comparison to the FrsMaterial type

These new features (most of them, anyway) are needed for making a more robust SVG exporter that supports holes in fills.

Reviewers: kjym3, campbellbarton

Subscribers: campbellbarton

Projects: #bf_blender

Differential Revision: https://developer.blender.org/D1245

1 files changed, 4 insertions, 2 deletions

diff --git a/release/scripts/freestyle/modules/freestyle/functions.py b/release/scripts/freestyle/modules/freestyle/functions.py
index 48d9b2e2b39..426d344e8ab 100644
--- a/release/scripts/freestyle/modules/freestyle/functions.py
+++ b/release/scripts/freestyle/modules/freestyle/functions.py
@@ -189,11 +189,13 @@ class CurveMaterialF0D(UnaryFunction0DMaterial):
     priority is used to pick one of the two materials at material
     boundaries.
 
-    Note: expects instances of CurvePoint to be iterated over
+    Notes: expects instances of CurvePoint to be iterated over
+           can return None if no fedge can be found
     """
     def __call__(self, inter):
         fe = inter.object.fedge
-        assert(fe is not None), "CurveMaterialF0D: fe is None"
+        if fe is None:
+            return None
         if fe.is_smooth:
             return fe.material
         else: