Fix assert in original modifiers pointer update function

The issue was happening with a specific file where the ID management
code was not fully copying all modifiers because of the extra check
in the `BKE_object_support_modifier_type_check()`.

While it is arguable that copy-on-write should be a 1:1 copy there is
no real need to maintain the per-modifier pointer to its original.
Use its SessionUUID to perform lookup in the original datablock.

Downside of this approach is that it is a linear lookup instead of
direct pointer access, but the upside is that there is less pointers
to manage and that the file with unsupported modifiers does behave
correct without any asserts.

Differential Revision: https://developer.blender.org/D13993

1 files changed, 5 insertions, 4 deletions

diff --git a/source/blender/makesrna/intern/rna_particle.c b/source/blender/makesrna/intern/rna_particle.c
index ff22a7758bb..23ec5148f00 100644
--- a/source/blender/makesrna/intern/rna_particle.c
+++ b/source/blender/makesrna/intern/rna_particle.c
@@ -249,7 +249,8 @@ static void rna_ParticleHairKey_location_object_get(PointerRNA *ptr, float *valu
  *
  * Such trickery is needed to allow modification of hair keys in the original object using
  * evaluated particle and object to access proper hair matrix. */
-static int hair_key_index_get(/*const*/ HairKey *hair_key,
+static int hair_key_index_get(const Object *object,
+                              /*const*/ HairKey *hair_key,
                               /*const*/ ParticleSystemModifierData *modifier,
                               /*const*/ ParticleData *particle)
 {
@@ -261,7 +262,7 @@ static int hair_key_index_get(/*const*/ HairKey *hair_key,
   const int particle_index = particle - particle_system->particles;
 
   const ParticleSystemModifierData *original_modifier = (ParticleSystemModifierData *)
-      BKE_modifier_get_original(&modifier->modifier);
+      BKE_modifier_get_original(object, &modifier->modifier);
   const ParticleSystem *original_particle_system = original_modifier->psys;
   const ParticleData *original_particle = &original_particle_system->particles[particle_index];
 
@@ -288,7 +289,7 @@ static void hair_key_location_object_set(HairKey *hair_key,
                                                                   NULL;
 
   if (hair_mesh != NULL) {
-    const int hair_key_index = hair_key_index_get(hair_key, modifier, particle);
+    const int hair_key_index = hair_key_index_get(object, hair_key, modifier, particle);
     if (hair_key_index == -1) {
       return;
     }
@@ -368,7 +369,7 @@ static void rna_ParticleHairKey_co_object_set(ID *id,
   /* Mark particle system as edited, so then particle_system_update() does not reset the hair
    * keys from path. This behavior is similar to how particle edit mode sets flags. */
   ParticleSystemModifierData *orig_modifier = (ParticleSystemModifierData *)
-      BKE_modifier_get_original(&modifier->modifier);
+      BKE_modifier_get_original(object, &modifier->modifier);
   orig_modifier->psys->flag |= PSYS_EDITED;
 
   hair_key_location_object_set(hair_key, object, modifier, particle, co);