Fix T70021: Alembic incomplete crease import

Creases are stored by the vertex indices of the edges. Sometimes they
were stored with (v1, v2) when the edge itself was stored with (v2, v1).
We now search for both orientations.

Sorting the vertex indices before searching avoids the second search
altogether when loading the example file of T70021.

1 files changed, 16 insertions, 3 deletions

diff --git a/source/blender/alembic/intern/abc_mesh.cc b/source/blender/alembic/intern/abc_mesh.cc
index 4d00b1904a8..12c59964a8c 100644
--- a/source/blender/alembic/intern/abc_mesh.cc
+++ b/source/blender/alembic/intern/abc_mesh.cc
@@ -1414,11 +1414,24 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
   Int32ArraySamplePtr indices = sample.getCreaseIndices();
   Alembic::Abc::FloatArraySamplePtr sharpnesses = sample.getCreaseSharpnesses();
 
-  MEdge *edges = mesh->medge;
-
   if (indices && sharpnesses) {
+    MEdge *edges = mesh->medge;
+    int totedge = mesh->totedge;
+
     for (int i = 0, s = 0, e = indices->size(); i < e; i += 2, s++) {
-      MEdge *edge = find_edge(edges, mesh->totedge, (*indices)[i], (*indices)[i + 1]);
+      int v1 = (*indices)[i];
+      int v2 = (*indices)[i + 1];
+
+      if (v2 < v1) {
+        /* It appears to be common to store edges with the smallest index first, in which case this
+         * prevents us from doing the second search below. */
+        std::swap(v1, v2);
+      }
+
+      MEdge *edge = find_edge(edges, totedge, v1, v2);
+      if (edge == NULL) {
+        edge = find_edge(edges, totedge, v2, v1);
+      }
 
       if (edge) {
         edge->crease = unit_float_to_uchar_clamp((*sharpnesses)[s]);