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I have four meshes with shape keys. Two cubes and two spheres. Across all meshes, the shape key names are identical and transform the meshes in similar ways. The shape keys on the first cube and the first sphere are animated with keyframes. Using this script (curtesey of @Harry McKenzie), it is possible to copy over the animated shape keys from Cube 1 to Cube 2 and from Sphere 1 to Sphere 2, because they have matching vertex counts respectively.

def copy_shape_keys(src, tgt):
    # Throw error if vertex count doesn't match
    if len(src.data.vertices) != len(tgt.data.vertices):
        raise RuntimeError('Objects have different vertex count!')

# Delete all shape keys of the target mesh
if tgt.data.shape_keys:
    for key in tgt.data.shape_keys.key_blocks:
        tgt.shape_key_remove(key)

keys = src.data.shape_keys

for key in keys.key_blocks:
    # Rebuild shape keys of target mesh using vertex data from source mesh
    k = tgt.shape_key_add(name=key.name, from_mix=False)
    for i, v in enumerate(src.data.vertices):
        k.data[i].co = key.data[i].co
    k.value = key.value

    # Create new action for every animated shape key
    data = tgt.data.shape_keys.animation_data_create()
    data.action = bpy.data.actions.new(name=key.name+"_action")

    # Copy fcurves from source to target
    for fc in keys.animation_data.action.fcurves:
        tgt_fc = data.action.fcurves.new(data_path=fc.data_path)
        for kf in fc.keyframe_points:
            tgt_fc.keyframe_points.insert(kf.co.x, kf.co.y)




source_obj = bpy.data.objects.get("Cube 1")
target_obj = bpy.data.objects.get("Cube 2")
copy_shape_keys(source_obj, target_obj)

Because this script relies on a perfect topology match, it fails to copy the animated shape keys from Cube 1 to any sphere or from Sphere 1 to any cube.

Animated shape keys on the right

How can this script be altered to allow all scenarios to work? In other words: How can this script be altered to only look at the shape key names, and not vertex data from other meshes, to copy over keyframes?

This question is a follow up to this thread.

Jonas Görke
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    It is not possible. Blender requires both shapes to have the same vertex count. Just create or dissolve vertices on the other shape to make them match count. – Harry McKenzie Aug 10 '23 at 01:35
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    Adding to @HarryMcKenzie's comment, the relevant doc part https://docs.blender.org/manual/en/latest/animation/shape_keys/introduction.html#adding-and-removing-vertices – taiyo Aug 10 '23 at 08:27
  • Is the only way to access shape key animations truly to copy all data from the ground up? Could there not be a more naive approach of just looking at the shape key value fields in the UI? It is easy to do manually by copy and pasting the keyframes into the timeline. – Jonas Görke Aug 10 '23 at 09:02
  • I would also like to add that using the script which was provided in the question of the original thread, it is possible to copy static shape key values from a cube to a sphere. Why can't this be extended to animated shape key values? – Jonas Görke Aug 10 '23 at 16:00

0 Answers0