[Bf-blender-cvs] [909e0819ae9] master: Fix T90532: Crash editing meshes with auto-smooth

[Campbell Barton]

Commit: 909e0819ae939a8054bea2c9dcf389232744f3ae
Author: Campbell Barton
Date:   Mon Aug 9 18:32:53 2021 +1000
Branches: master
https://developer.blender.org/rB909e0819ae939a8054bea2c9dcf389232744f3ae

Fix T90532: Crash editing meshes with auto-smooth

Caused by fix for T90256 and a misunderstanding in D11928.

Don't skip tagging edges when the auto-smooth angle is 180 degrees
since this skips topology checks which are needed for properly
calculating edge loop normals.

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

M	source/blender/bmesh/intern/bmesh_mesh_normals.c

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

diff --git a/source/blender/bmesh/intern/bmesh_mesh_normals.c b/source/blender/bmesh/intern/bmesh_mesh_normals.c
index 8eda38046a1..a5e41b74ee1 100644
--- a/source/blender/bmesh/intern/bmesh_mesh_normals.c
+++ b/source/blender/bmesh/intern/bmesh_mesh_normals.c
@@ -1116,8 +1116,6 @@ static void bm_mesh_loops_calc_normals__single_threaded(BMesh *bm,
   BMIter fiter;
   BMFace *f_curr;
   const bool has_clnors = clnors_data || (cd_loop_clnors_offset != -1);
-  const bool check_angle = (split_angle < (float)M_PI);
-  const float split_angle_cos = check_angle ? cosf(split_angle) : -1.0f;
 
   MLoopNorSpaceArray _lnors_spacearr = {NULL};
 
@@ -1152,16 +1150,13 @@ static void bm_mesh_loops_calc_normals__single_threaded(BMesh *bm,
     do {
       BM_elem_index_set(l_curr, index_loop++); /* set_inline */
       BM_elem_flag_disable(l_curr, BM_ELEM_TAG);
-      /* Needed for when #bm_mesh_edges_sharp_tag doesn't run.
-       * Mark smooth if there is no smoothing angle. */
-      BM_elem_flag_enable(l_curr->e, BM_ELEM_TAG);
     } while ((l_curr = l_curr->next) != l_first);
   }
   bm->elem_index_dirty &= ~(BM_FACE | BM_LOOP);
 
-  if (split_angle_cos != -1.0f) {
-    bm_mesh_edges_sharp_tag(bm, fnos, has_clnors ? (float)M_PI : split_angle, false);
-  }
+  /* Always tag edges based on winding & sharp edge flag
+   * (even when the auto-smooth angle doesn't need to be calculated). */
+  bm_mesh_edges_sharp_tag(bm, fnos, has_clnors ? (float)M_PI : split_angle, false);
 
   /* We now know edges that can be smoothed (they are tagged),
    * and edges that will be hard (they aren't).