Fix T94600: Apply single shrinkwrap constraint fails

rBd6891d9bee2b introduced a way to apply a single constraint from the
constraint stack. For this we want to work in the evaluated domain, in
particular the constraint target should be evaluated (the shrinkwrap
constraint needs to have access to the target's evaluated mesh).

Thx a lot to @sergey for handholding here!

Maniphest Tasks: T94600

Differential Revision: https://developer.blender.org/D13765

1 files changed, 24 insertions, 10 deletions

diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index 312feae4665..2a5afb6be9a 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -34,6 +34,7 @@
 
 #include "BLI_blenlib.h"
 #include "BLI_kdopbvh.h"
+#include "BLI_listbase.h"
 #include "BLI_math.h"
 #include "BLI_string_utils.h"
 #include "BLI_utildefines.h"
@@ -5676,13 +5677,19 @@ bool BKE_constraint_apply_for_object(Depsgraph *depsgraph,
 
   const float ctime = BKE_scene_frame_get(scene);
 
-  bConstraint *new_con = BKE_constraint_duplicate_ex(con, 0, !ID_IS_LINKED(ob));
+  /* Do this all in the evaluated domain (e.g. shrinkwrap needs to access evaluated constraint
+   * target mesh). */
+  Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
+  Object *ob_eval = DEG_get_evaluated_object(depsgraph, ob);
+  bConstraint *con_eval = BKE_constraints_find_name(&ob_eval->constraints, con->name);
+
+  bConstraint *new_con = BKE_constraint_duplicate_ex(con_eval, 0, !ID_IS_LINKED(ob));
   ListBase single_con = {new_con, new_con};
 
   bConstraintOb *cob = BKE_constraints_make_evalob(
-      depsgraph, scene, ob, NULL, CONSTRAINT_OBTYPE_OBJECT);
+      depsgraph, scene_eval, ob_eval, NULL, CONSTRAINT_OBTYPE_OBJECT);
   /* Undo the effect of the current constraint stack evaluation. */
-  mul_m4_m4m4(cob->matrix, ob->constinv, cob->matrix);
+  mul_m4_m4m4(cob->matrix, ob_eval->constinv, cob->matrix);
 
   /* Evaluate single constraint. */
   BKE_constraints_solve(depsgraph, &single_con, cob, ctime);
@@ -5695,7 +5702,7 @@ bool BKE_constraint_apply_for_object(Depsgraph *depsgraph,
   BLI_freelinkN(&single_con, new_con);
 
   /* Apply transform from matrix. */
-  BKE_object_apply_mat4(ob, ob->obmat, true, true);
+  BKE_object_apply_mat4(ob, ob_eval->obmat, true, true);
 
   return true;
 }
@@ -5722,18 +5729,25 @@ bool BKE_constraint_apply_for_pose(
 
   const float ctime = BKE_scene_frame_get(scene);
 
-  bConstraint *new_con = BKE_constraint_duplicate_ex(con, 0, !ID_IS_LINKED(ob));
+  /* Do this all in the evaluated domain (e.g. shrinkwrap needs to access evaluated constraint
+   * target mesh). */
+  Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
+  Object *ob_eval = DEG_get_evaluated_object(depsgraph, ob);
+  bPoseChannel *pchan_eval = BKE_pose_channel_find_name(ob_eval->pose, pchan->name);
+  bConstraint *con_eval = BKE_constraints_find_name(&pchan_eval->constraints, con->name);
+
+  bConstraint *new_con = BKE_constraint_duplicate_ex(con_eval, 0, !ID_IS_LINKED(ob));
   ListBase single_con;
   single_con.first = new_con;
   single_con.last = new_con;
 
   float vec[3];
-  copy_v3_v3(vec, pchan->pose_mat[3]);
+  copy_v3_v3(vec, pchan_eval->pose_mat[3]);
 
   bConstraintOb *cob = BKE_constraints_make_evalob(
-      depsgraph, scene, ob, pchan, CONSTRAINT_OBTYPE_BONE);
+      depsgraph, scene_eval, ob_eval, pchan_eval, CONSTRAINT_OBTYPE_BONE);
   /* Undo the effects of currently applied constraints. */
-  mul_m4_m4m4(cob->matrix, pchan->constinv, cob->matrix);
+  mul_m4_m4m4(cob->matrix, pchan_eval->constinv, cob->matrix);
   /* Evaluate single constraint. */
   BKE_constraints_solve(depsgraph, &single_con, cob, ctime);
   BKE_constraints_clear_evalob(cob);
@@ -5744,12 +5758,12 @@ bool BKE_constraint_apply_for_pose(
 
   /* Prevent constraints breaking a chain. */
   if (pchan->bone->flag & BONE_CONNECTED) {
-    copy_v3_v3(pchan->pose_mat[3], vec);
+    copy_v3_v3(pchan_eval->pose_mat[3], vec);
   }
 
   /* Apply transform from matrix. */
   float mat[4][4];
-  BKE_armature_mat_pose_to_bone(pchan, pchan->pose_mat, mat);
+  BKE_armature_mat_pose_to_bone(pchan, pchan_eval->pose_mat, mat);
   BKE_pchan_apply_mat4(pchan, mat, true);
 
   return true;