Transfer matrices from a bone space to another

snippets/bpy/dump_matrix_in_bone_space_and_transfer.py

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+## Dump matrices of objects relative to a bone space and apply on another one
+
+import bpy
+import mathutils
+import json
+
+### Convert an object matrix to bone space
+
+def convert_attr(Attr):
+    '''Convert given value to a Json serializable format'''
+    if isinstance(Attr, (mathutils.Vector,mathutils.Color)):
+        return Attr[:]
+    elif isinstance(Attr, mathutils.Matrix):
+        return [v[:] for v in Attr]
+    elif isinstance(Attr,bpy.types.bpy_prop_array):
+        return [Attr[i] for i in range(0,len(Attr))]
+    else:
+        return(Attr)
+
+obj = bpy.data.objects['char_rig']
+ref_bone = obj.pose.bones["hips"]
+
+scn = bpy.context.scene
+
+d = {}
+for i in range(scn.frame_start, scn.frame_end+1):
+    # scn.frame_current = i
+    scn.frame_set(i) # actually refresh
+
+    ob_dict = {}
+    ## using selection
+    for ob in bpy.context.selected_objects:
+        ob_dict[ob.name] = convert_attr(ref_bone.matrix.inverted() @ ob.matrix_world)
+
+    ## using a list of names
+    # for ob_name in ['obj_name_01', 'obj_name_02']:
+    #     ob = scn.objects.get(ob_name)
+    #     if not ob:
+    #         continue
+    #     ob_dict[ob_name] = convert_attr(ref_bone.matrix.inverted() @ ob.matrix_world)
+
+    if ob_dict:
+        d[i] = ob_dict
+
+## dict ex: d = { 100 : {'ob_name_01' : Matrix} }
+
+## Set to clipboard
+bpy.context.window_manager.clipboard = json.dumps(d, indent='\t')
+
+
+## -------------------------
+
+
+### Apply dumped value on new bone space
+
+## load from clipboard
+d = json.loads(bpy.context.window_manager.clipboard)
+
+obj = bpy.data.objects['char_rig']
+ref_bone = obj.pose.bones["hips"]
+
+for k, ob_dic in d.items():
+    i = int(k)
+    scn.frame_set(i) # set frame and refresh data
+    print(scn.frame_current)
+
+    ## Set all objects in dict ()
+    for ob_name, mat_in_bone_space in ob_dic.items():
+        ob = scn.objects.get(ob_name)
+        if not ob:
+            continue
+
+        ob.matrix_world = ref_bone.matrix @ mathutils.Matrix(mat_in_bone_space)
+
+        ## Add keyframe
+        for chan in ('location', 'rotation_euler'):
+            # if has_channel_key_at_frame(ob, channel=chan):
+            #     # key only when needed...
+            #     ob.keyframe_insert(chan,frame=i)
+            ob.keyframe_insert(chan, frame=i)