Disable Constraint and Keep Transform

A 'Disable and Keep Transform' button for constraints was added. This
allows animators to disable a constraint without moving the constrained
object/bone, making it easier to toggle constriants on and off without
any visual consequence. Typical usage would be a character picking up an
object (enable 'Copy Transform' constraint) and placing it somewhere
else (disable the constraint).

Note that there could still be movement when there are muliple
constraints active. For example, when using this constraint stack

- #1: Copy Transform from Empty.001
- #2: Copy Rotation from Empty.002

and disabling constraint #2, constraint #1 is still active and will
still modify the visual transform of the object. According to our
in-house animators, this is expected behaviour.

Reviewers: campbellbarton, dfelinto, sergey

Reviewed By: campbellbarton

Subscribers: brecht

Tags: #animation

Differential Revision: https://developer.blender.org/D4677

1 files changed, 11 insertions, 1 deletions

diff --git a/release/scripts/startup/bl_ui/properties_constraint.py b/release/scripts/startup/bl_ui/properties_constraint.py
index f5b36d6cfd0..310d35c6179 100644
--- a/release/scripts/startup/bl_ui/properties_constraint.py
+++ b/release/scripts/startup/bl_ui/properties_constraint.py
@@ -34,8 +34,18 @@ class ConstraintButtonsPanel:
             # match enum type to our functions, avoids a lookup table.
             getattr(self, con.type)(context, box, con)
 
-            if con.type not in {'RIGID_BODY_JOINT', 'NULL'}:
+            if con.type in {'RIGID_BODY_JOINT', 'NULL'}:
+                return
+
+            if con.type in {'IK', 'SPLINE_IK'}:
+                # constraint.disable_keep_transform doesn't work well
+                # for these constraints.
                 box.prop(con, "influence")
+            else:
+                row = box.row(align=True)
+                row.prop(con, "influence")
+                row.operator("constraint.disable_keep_transform",
+                    text='', icon='CANCEL')
 
     @staticmethod
     def space_template(layout, con, target=True, owner=True):