Transform: generalized custom-data correction support

Support custom-data correction based on surrounding geometry for all
transformation modes of the mesh transform operators.

The is the same logic used in Vert and Edge Slide.

In order not to change the current default behavior,
this property does not affect Vert and Edge Slide modes.

1 files changed, 15 insertions, 3 deletions

diff --git a/source/blender/bmesh/intern/bmesh_interp.c b/source/blender/bmesh/intern/bmesh_interp.c
index 27c03f0a84f..82502227a9a 100644
--- a/source/blender/bmesh/intern/bmesh_interp.c
+++ b/source/blender/bmesh/intern/bmesh_interp.c
@@ -744,9 +744,21 @@ void BM_loop_interp_from_face(
   float co[2];
   int i;
 
-  /* convert the 3d coords into 2d for projection */
-  BLI_assert(BM_face_is_normal_valid(f_src));
-  axis_dominant_v3_to_m3(axis_mat, f_src->no);
+  /* Convert the 3d coords into 2d for projection. */
+  float axis_dominant[3];
+  if (!is_zero_v3(f_src->no)) {
+    BLI_assert(BM_face_is_normal_valid(f_src));
+    copy_v3_v3(axis_dominant, f_src->no);
+  }
+  else {
+    /* Rare case in which all the vertices of the face are aligned.
+     * Get a random axis that is orthogonal to the tangent. */
+    float vec[3];
+    BM_face_calc_tangent_auto(f_src, vec);
+    ortho_v3_v3(axis_dominant, vec);
+    normalize_v3(axis_dominant);
+  }
+  axis_dominant_v3_to_m3(axis_mat, axis_dominant);
 
   i = 0;
   l_iter = l_first = BM_FACE_FIRST_LOOP(f_src);