Python copy animation from armature to another armature different rest pose

Question

I have two armatures with different rest pose I wonder if there is a proper way to copy the animation from on the other as shown in the image.

Here is an example of the blend file https://ufile.io/7h1l48gv

this the code attempt for one frame but it didn't work as expected .

pos_bones = bpy.data.objects["Uncorrect"].pose.bones
pos_bones1 = bpy.data.objects["Correct"].pose.bones
for bon in range(0,len(pos_bones)):
    bone = pos_bones[bon]
    matrixPoseOrignal = pos_bones1[bon].matrix
    matrixLocalChanged = bpy.data.objects["Uncorrect"].data.bones[bone.name].matrix_local
bone.matrix = matrixLocalChanged
mat = matrixPoseOrignal.inverted() @ bone.matrix
bone.matrix = mat

Answer 1

Make constraints to visualize, then convert.

Not at all sure how the code in question is going to even be close to what you wish to achieve.

Would look at doing something akin to answer here.

PoseBone local rotation values to global with axis changed

The last example of which shows how to run thru pose bones, convert space, change the alignment and convert back.

Create pose from existing armature

This one has two armatures with two distinct rest poses, (the one with animation is an abomination) To create the animation on t pose rig from other have added constraints to copy the transforms from source to target, then loop thru and create the animation.

For your example since the bones are not using same axes, could instead copy location to but "Incorrect" bones heads at "Correct" bones heads, and use a track to constraint.

Script to constraint target pose bones to source.

import bpy
from math import pi
context = bpy.context
scene = context.scene
source = scene.objects.get("Correct")
Incorrect (sp)
target = scene.objects.get("Uncorrect")
target.animation_data_clear() # remove any ad
for pbc, pbi in zip(source.pose.bones, target.pose.bones):
    # clear  for testing
    while pbi.constraints:
        pbi.constraints.remove(pbi.constraints[0])
# locations

cl = pbi.constraints.new('COPY_LOCATION')
cl.target = pbc.id_data
cl.subtarget = pbc.name
cl.owner_space = 'POSE'
cl.target_space = 'POSE'

# rotations

tt = pbi.constraints.new('TRACK_TO')
tt.target = pbc.id_data
tt.subtarget = pbc.name
tt.owner_space = 'POSE'
tt.target_space = 'POSE' 
tt.head_tail = 1
tt.track_axis = 'TRACK_X'
tt.up_axis = 'UP_Z'
tt.use_target_z = True  

Script to convert constraints to keyframe animation

import bpy
from math import pi
context = bpy.context
scene = context.scene
remove_constraints = True
source = scene.objects.get("Correct")
Incorrect (sp)
target = scene.objects.get("Uncorrect")
action = source.animation_data.action
f = action.frame_range.x
add a keyframe to each frame of new rig
while f <= action.frame_range.y:
    scene.frame_set(f)
    context.view_layer.update()
    r2 = target.evaluated_get(context.evaluated_depsgraph_get())
    for pb in target.pose.bones:
        #pb2 = rig1.pose.bones.get(pb.name)
        m = r2.convert_space(
            pose_bone=pb, 
            matrix=pb.matrix, 
            from_space='POSE',
            to_space='LOCAL',
            )
        if pb.rotation_mode == 'QUATERNION':
            pb.rotation_quaternion = m.to_quaternion()
            pb.keyframe_insert("rotation_quaternion", frame=f)
        else:
    # add rot mode checking 
        pb.rotation_euler = m.to_euler(pb.rotation_mode)
        pb.keyframe_insert(&quot;rotation_euler&quot;, frame=f)
    pb.location = m.to_translation()

    pb.keyframe_insert(&quot;location&quot;, frame=f)
f += 1


for pb in target.pose.bones:
    # clear  for testing
    while pb.constraints:
        pb.constraints.remove(pb.constraints[0])