Bones with overlapping IK constraints would jump about unpredictably
when at least one of those constraints was either zero-influence or
disabled.
The underlying issue appears to be that depsgraph construction assumes
all IK constraints are enabled (which is necessary for e.g. animating
influence), but the IK solver code excludes disabled and zero-influence
constraints from the solve. This in turn leads to
`BKE_pose_where_is_bone` not getting called when needed in some cases.
This commit addresses the issue by always including all IK targets in
the solve even when disabled or zero-influence, and simply excluding
them from being applied.
See the discussion in #88752 for more details.
This patch was primarily authored by Brecht, but with a minor fix
by me after testing.
Co-authored-by: Brecht Van Lommel <brecht@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/110417
6b872079fe