Fix T67232: Multiples targetless IKs in a chain gives weird behaviour (known as FakeIK for FK posing)

The issue was that the deps graph relation builder assumed that all
bones that had a IK constraint on them would be evaluated.  However for
targetless IK bones, only the active bone would receive updates and the
others would be skipped (as those would be treated as if the IK
constraint was disabled).

I didn't see an easy way to solve this from the depsgraph side of
things.

Instead I came up with a solution that I feel is quite strait forward
and reflects what is actually supposed to happen under the hood.

Now all targetless IK constraints are treated as disabled and will not
be added to any relations in the depsgraph.

Instead, a temporary IK constraint will be created when the bone in
question is transformed.  This is basically activating "Auto IK" for the
bone while transforming.

Reviewed By: Sergey, Brecht

Differential Revision: http://developer.blender.org/D7378

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/depsgraph/intern/builder/deg_builder_relations_rig.cc b/source/blender/depsgraph/intern/builder/deg_builder_relations_rig.cc
index 6fe9a3c2a00..d05385a7d7c 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_relations_rig.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_relations_rig.cc
@@ -68,6 +68,12 @@ void DepsgraphRelationBuilder::build_ik_pose(Object *object,
                                              bConstraint *con,
                                              RootPChanMap *root_map)
 {
+  if ((con->flag & CONSTRAINT_DISABLE) != 0) {
+    /* Do not add disabled IK constraints to the relations. If these needs to be temporarly
+     * enabled, they will be added as temporary constraints during transform. */
+    return;
+  }
+
   bKinematicConstraint *data = (bKinematicConstraint *)con->data;
   /* Attach owner to IK Solver to. */
   bPoseChannel *rootchan = BKE_armature_ik_solver_find_root(pchan, data);