Fix T61391: MeshDeform Modifier does not work on a solidified planar mesh.

`BKE_modifier_get_evaluated_mesh_from_evaluated_object()` used by
modifiers needing access to other objects' geometry probably skipped out
of the radar when cage and final evaluated meshes were added to
BMEditMesh? In any case, we do not need to duplicate (and then free!) a
temp mesh from editdata anymore, and we can even add instead a parameter
to get cage instead of final. Also makes modifiers code a bit simpler.

1 files changed, 8 insertions, 7 deletions

diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index 511f5d01461..9e24131ddd3 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -899,23 +899,24 @@ struct DerivedMesh *modifier_applyModifier_DM_deprecated(
  * Get evaluated mesh for other evaluated object, which is used as an operand for the modifier,
  * e.g. second operand for boolean modifier.
  * Note that modifiers in stack always get fully evaluated COW ID pointers, never original ones. Makes things simpler.
+ *
+ * \param get_cage_mesh Return evaluated mesh with only deforming modifiers applied
+ *                      (i.e. mesh topology remains the same as original one, a.k.a. 'cage' mesh).
  */
-Mesh *BKE_modifier_get_evaluated_mesh_from_evaluated_object(Object *ob_eval, bool *r_free_mesh)
+Mesh *BKE_modifier_get_evaluated_mesh_from_evaluated_object(Object *ob_eval, const bool get_cage_mesh)
 {
 	Mesh *me = NULL;
 
 	if ((ob_eval->type == OB_MESH) && (ob_eval->mode & OB_MODE_EDIT)) {
-		/* Note: currently we have no equivalent to derived cagemesh or even final dm in BMEditMesh...
-		 * This is TODO in core depsgraph/modifier stack code still. */
+		/* In EditMode, evaluated mesh is stored in BMEditMesh, not the object... */
 		BMEditMesh *em = BKE_editmesh_from_object(ob_eval);
 		if (em != NULL) {  /* em might not exist yet in some cases, just after loading a .blend file, see T57878. */
-			me = BKE_mesh_from_bmesh_for_eval_nomain(em->bm, 0);
-			*r_free_mesh = true;
+			me = (get_cage_mesh && em->mesh_eval_cage != NULL) ? em->mesh_eval_cage : em->mesh_eval_final;
 		}
 	}
 	if (me == NULL) {
-		me = ob_eval->runtime.mesh_eval;
-		*r_free_mesh = false;
+		me = (get_cage_mesh && ob_eval->runtime.mesh_deform_eval != NULL) ? ob_eval->runtime.mesh_deform_eval :
+		                                                                    ob_eval->runtime.mesh_eval;
 	}
 
 	return me;