Copy Rotation: implement new mixing modes that actually work.

Upon close inspection, the way the Offset mode works in the
Copy Rotation constraint makes no sense, and in fact, destroys
the rotation of its owner unless either it's single axis, or
the order is set specifically to `ZYX Euler`.

Since it can't simply be changed because of backward compatibility
concerns, replace the checkbox with a dropdown that provides a set
of new modes that actually make sense.

Specifically, add a mode that simply adds Euler components together,
and two options that use matrix multiplication in different order.

The Python use_offset property is replaced with compatibility stubs.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5640

1 files changed, 23 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/versioning_280.c b/source/blender/blenloader/intern/versioning_280.c
index 54d2bd8499f..0d108704b4e 100644
--- a/source/blender/blenloader/intern/versioning_280.c
+++ b/source/blender/blenloader/intern/versioning_280.c
@@ -727,6 +727,17 @@ static void do_version_constraints_copy_scale_power(ListBase *lb)
   }
 }
 
+static void do_version_constraints_copy_rotation_mix_mode(ListBase *lb)
+{
+  for (bConstraint *con = lb->first; con; con = con->next) {
+    if (con->type == CONSTRAINT_TYPE_ROTLIKE) {
+      bRotateLikeConstraint *data = (bRotateLikeConstraint *)con->data;
+      data->mix_mode = (data->flag & ROTLIKE_OFFSET) ? ROTLIKE_MIX_OFFSET : ROTLIKE_MIX_REPLACE;
+      data->flag &= ~ROTLIKE_OFFSET;
+    }
+  }
+}
+
 static void do_versions_seq_alloc_transform_and_crop(ListBase *seqbase)
 {
   for (Sequence *seq = seqbase->first; seq != NULL; seq = seq->next) {
@@ -3797,5 +3808,17 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
         do_version_bones_inherit_scale(&arm->bonebase);
       }
     }
+
+    /* Convert the Offset flag to the mix mode enum. */
+    if (!DNA_struct_elem_find(fd->filesdna, "bRotateLikeConstraint", "char", "mix_mode")) {
+      LISTBASE_FOREACH (Object *, ob, &bmain->objects) {
+        do_version_constraints_copy_rotation_mix_mode(&ob->constraints);
+        if (ob->pose) {
+          LISTBASE_FOREACH (bPoseChannel *, pchan, &ob->pose->chanbase) {
+            do_version_constraints_copy_rotation_mix_mode(&pchan->constraints);
+          }
+        }
+      }
+    }
   }
 }