Fix T96294: Crash and error with shape key normal calculation

A mistake in the mesh normal refactor caused the wrong mesh to
be used when calculating normals with a shape key's deformation.

This commit fixes the normal calculation by using the correct mesh,
with just adjusted vertex positions, and calculating the results
directly into the result arrays when possible. This completely avoids
the need to make a local copy of the mesh, which makes sense,
since the only thing that changes is the vertex positions.

Differential Revision: https://developer.blender.org/D14317

1 files changed, 60 insertions, 53 deletions

diff --git a/source/blender/blenkernel/intern/key.c b/source/blender/blenkernel/intern/key.c
index 11d6e6ef973..5247e9f358b 100644
--- a/source/blender/blenkernel/intern/key.c
+++ b/source/blender/blenkernel/intern/key.c
@@ -2171,16 +2171,14 @@ void BKE_keyblock_convert_from_mesh(Mesh *me, Key *key, KeyBlock *kb)
   BKE_keyblock_update_from_mesh(me, kb);
 }
 
-void BKE_keyblock_convert_to_mesh(KeyBlock *kb, Mesh *me)
+void BKE_keyblock_convert_to_mesh(KeyBlock *kb, struct MVert *mvert, int totvert)
 {
-  MVert *mvert;
   const float(*fp)[3];
   int a, tot;
 
-  mvert = me->mvert;
   fp = kb->data;
 
-  tot = min_ii(kb->totelem, me->totvert);
+  tot = min_ii(kb->totelem, totvert);
 
   for (a = 0; a < tot; a++, fp++, mvert++) {
     copy_v3_v3(mvert->co, *fp);
@@ -2193,68 +2191,77 @@ void BKE_keyblock_mesh_calc_normals(struct KeyBlock *kb,
                                     float (*r_polynors)[3],
                                     float (*r_loopnors)[3])
 {
-  /* We use a temp, shallow copy of mesh to work. */
-  Mesh me;
-  bool free_polynors = false;
-
   if (r_vertnors == NULL && r_polynors == NULL && r_loopnors == NULL) {
     return;
   }
 
-  me = *mesh;
-  me.mvert = MEM_dupallocN(mesh->mvert);
-  CustomData_reset(&me.vdata);
-  CustomData_reset(&me.edata);
-  CustomData_reset(&me.pdata);
-  CustomData_reset(&me.ldata);
-  CustomData_reset(&me.fdata);
-
-  BKE_keyblock_convert_to_mesh(kb, &me);
-
-  if (r_polynors == NULL && r_loopnors != NULL) {
-    r_polynors = MEM_mallocN(sizeof(float[3]) * me.totpoly, __func__);
-    free_polynors = true;
-  }
-
-  const float(*vert_normals)[3] = BKE_mesh_vertex_normals_ensure(mesh);
-  if (r_vertnors) {
-    memcpy(r_vertnors, vert_normals, sizeof(float[3]) * me.totvert);
-  }
-
-  const float(*face_normals)[3] = BKE_mesh_poly_normals_ensure(mesh);
-  memcpy(r_polynors, face_normals, sizeof(float[3]) * me.totpoly);
-
-  if (r_loopnors) {
+  MVert *mvert = MEM_dupallocN(mesh->mvert);
+  BKE_keyblock_convert_to_mesh(kb, mesh->mvert, mesh->totvert);
+
+  const bool loop_normals_needed = r_loopnors != NULL;
+  const bool vert_normals_needed = r_vertnors != NULL || loop_normals_needed;
+  const bool poly_normals_needed = r_polynors != NULL || vert_normals_needed ||
+                                   loop_normals_needed;
+
+  float(*vert_normals)[3] = r_vertnors;
+  float(*poly_normals)[3] = r_polynors;
+  bool free_vert_normals = false;
+  bool free_poly_normals = false;
+  if (vert_normals_needed && r_vertnors == NULL) {
+    vert_normals = MEM_malloc_arrayN(mesh->totvert, sizeof(float[3]), __func__);
+    free_vert_normals = true;
+  }
+  if (poly_normals_needed && r_polynors == NULL) {
+    poly_normals = MEM_malloc_arrayN(mesh->totpoly, sizeof(float[3]), __func__);
+    free_poly_normals = true;
+  }
+
+  if (poly_normals_needed) {
+    BKE_mesh_calc_normals_poly(mvert,
+                               mesh->totvert,
+                               mesh->mloop,
+                               mesh->totloop,
+                               mesh->mpoly,
+                               mesh->totpoly,
+                               poly_normals);
+  }
+  if (vert_normals_needed) {
+    BKE_mesh_calc_normals_poly_and_vertex(mvert,
+                                          mesh->totvert,
+                                          mesh->mloop,
+                                          mesh->totloop,
+                                          mesh->mpoly,
+                                          mesh->totpoly,
+                                          poly_normals,
+                                          vert_normals);
+  }
+  if (loop_normals_needed) {
     short(*clnors)[2] = CustomData_get_layer(&mesh->ldata, CD_CUSTOMLOOPNORMAL); /* May be NULL. */
-
-    BKE_mesh_normals_loop_split(me.mvert,
+    BKE_mesh_normals_loop_split(mesh->mvert,
                                 vert_normals,
-                                me.totvert,
-                                me.medge,
-                                me.totedge,
-                                me.mloop,
+                                mesh->totvert,
+                                mesh->medge,
+                                mesh->totedge,
+                                mesh->mloop,
                                 r_loopnors,
-                                me.totloop,
-                                me.mpoly,
-                                face_normals,
-                                me.totpoly,
-                                (me.flag & ME_AUTOSMOOTH) != 0,
-                                me.smoothresh,
+                                mesh->totloop,
+                                mesh->mpoly,
+                                poly_normals,
+                                mesh->totpoly,
+                                (mesh->flag & ME_AUTOSMOOTH) != 0,
+                                mesh->smoothresh,
                                 NULL,
                                 clnors,
                                 NULL);
   }
 
-  CustomData_free(&me.vdata, me.totvert);
-  CustomData_free(&me.edata, me.totedge);
-  CustomData_free(&me.pdata, me.totpoly);
-  CustomData_free(&me.ldata, me.totloop);
-  CustomData_free(&me.fdata, me.totface);
-  MEM_freeN(me.mvert);
-
-  if (free_polynors) {
-    MEM_freeN(r_polynors);
+  if (free_vert_normals) {
+    MEM_freeN(vert_normals);
+  }
+  if (free_poly_normals) {
+    MEM_freeN(poly_normals);
   }
+  MEM_freeN(mvert);
 }
 
 /************************* raw coords ************************/