Commit: 7c6d546f3a72569e15285bc046345b7f60df2aaa
Author: Howard Trickey
Date: Sat Jul 23 12:15:59 2022 -0400
Branches: master
https://developer.blender.org/rB7c6d546f3a72569e15285bc046345b7f60df2aaa
Fix an assert trip in boolean tickled by D11272 example.
The face merging code in exact boolean made an assumption that
the tesselated original face was manifold except at the boundaries.
This should be true but sometimes (e.g., if the input faces have
self-intersection, as happens in the example), it is not.
This commit makes face merging tolerant of such a situation.
It might leave some stray edges from triangulation, but it should
only happen if the input is malformed.
Note: the input may be malformed if there were previous booleans
in the stack, since snapping the exact result to float coordinates
is not guaranteed to leave the mesh without defects.
This is the second try at this commit. The previous one had a typo
in it -- luckily, the tests caught the problem.
===================================================================
M source/blender/blenlib/intern/mesh_boolean.cc
===================================================================
diff --git a/source/blender/blenlib/intern/mesh_boolean.cc
b/source/blender/blenlib/intern/mesh_boolean.cc
index 700c126ca4c..d4586f95fe0 100644
--- a/source/blender/blenlib/intern/mesh_boolean.cc
+++ b/source/blender/blenlib/intern/mesh_boolean.cc
@@ -2966,6 +2966,11 @@ static std::ostream &operator<<(std::ostream &os, const
FaceMergeState &fms)
* \a tris all have the same original face.
* Find the 2d edge/triangle topology for these triangles, but only the ones
facing in the
* norm direction, and whether each edge is dissolvable or not.
+ * If we did the initial triangulation properly, and any Delaunay
triangulations of interections
+ * properly, then each triangle edge should have at most one neighbor.
+ * However, there can be anonalies. For example, if an input face is
self-intersecting, we fall
+ * back on the floating poing polyfill triangulation, which, after which all
bets are off.
+ * Hence, try to be tolerant of such unexpected topology.
*/
static void init_face_merge_state(FaceMergeState *fms,
const Vector<int> &tris,
@@ -3053,16 +3058,35 @@ static void init_face_merge_state(FaceMergeState *fms,
std::cout << "me.v1 == mf.vert[i] so set edge[" << me_index <<
"].left_face = " << f
<< "\n";
}
- BLI_assert(me.left_face == -1);
- fms->edge[me_index].left_face = f;
+ if (me.left_face != -1) {
+ /* Unexpected in the normal case: this means more than one triangle
shares this
+ * edge in the same orientation. But be tolerant of this case. By
making this
+ * edge not dissolvable, we'll avoid future problems due to this
non-manifold topology.
+ */
+ if (dbg_level > 1) {
+ std::cout << "me.left_face was already occupied, so triangulation
wasn't good\n";
+ }
+ me.dissolvable = false;
+ }
+ else {
+ fms->edge[me_index].left_face = f;
+ }
}
else {
if (dbg_level > 1) {
std::cout << "me.v1 != mf.vert[i] so set edge[" << me_index <<
"].right_face = " << f
<< "\n";
}
- BLI_assert(me.right_face == -1);
- fms->edge[me_index].right_face = f;
+ if (me.right_face != -1) {
+ /* Unexpected, analogous to the me.left_face != -1 case above. */
+ if (dbg_level > 1) {
+ std::cout << "me.right_face was already occupied, so triangulation
wasn't good\n";
+ }
+ me.dissolvable = false;
+ }
+ else {
+ fms->edge[me_index].right_face = f;
+ }
}
fms->face[f].edge.append(me_index);
}
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