Two armature, two rest pose, fixing animations

Question

So I have one FBX that have it's own armature and one object. Let's call it T pose. I have second FBX that contains one armature with let's say walk animation.

I am trying to assign walk animation to object with t-pose with no success. What have I tried so far:

• Adding just walk armature to object won't work. I mean I can add the armature, but walk armature's rest pose is different than t-pose's rest pose. If I just change armature, animation is awkward.

• I wrote one simple Python script that copy rest pose of walk animation and paste it to rest pose of t-pose. That didn't helped.

• tried Copying FBX animation to armature

Am I right that deformations in animations are just offsets from rest pose?

I see others had same problems like: Merge multiple fbx animations into single rig or Import fbx animation

Is there any solution for this? Any comment is appreciated.

Answer 1

The solution is rather simple.

You need to add Bone Constraint -> Copy Transforms to armature without animation. As Target add armature with animation, and as a Bone, bone with the same name. Rinse and repeat for all bones.

Here is the code that automates all:

• Creates constraints and link bones with other armature
• Iterate over all frames, apply transform, and insert keyframes for all bones
• Delete constrains

Just fill source and target armature, and animation from and to. Moreover, you can just call add_constraints() function which will link armatures and bones.

import bpy

source = "Bip001"
target = "Bip001.001"
frame_from = 0
frame_to = 35

# add constrains and link them with target bones
def add_constraints():
    global source, target
    
    source_ob = bpy.data.objects[source]
    
    for bone in source_ob.pose.bones:
        sel_bone=source_ob.data.bones[bone.name]
        sel_bone.select=True
        bpy.context.object.data.bones.active=sel_bone

        trans_bone = bpy.context.object.pose.bones[bone.name]
        if trans_bone.constraints.find('Copy Transforms') == -1:
            if bpy.data.objects[target].pose.bones.get(bone.name) is not None:
                bpy.ops.pose.constraint_add(type='COPY_TRANSFORMS')
                trans_bone.constraints["Copy Transforms"].target = bpy.data.objects[target]
                trans_bone.constraints["Copy Transforms"].subtarget = bone.name

# delete previously created constrains     
def del_constraints( ):
    for bone in bpy.context.selected_pose_bones:
        copyLocConstraints = [ c for c in bone.constraints if c.type == 'COPY_TRANSFORMS' ]
        # Iterate over all the bone's copy location constraints and delete them all
        for c in copyLocConstraints:
            bone.constraints.remove( c ) # Remove constraint

def apply_animation():
    global source, target, frame_from, frame_to
    #set keying set to whole character
    #we have all bones selected
    scene = bpy.context.scene
    for frame in range(frame_from, frame_to ):
        scene.frame_current = frame
        scene.frame_set(scene.frame_current)
        # apply visual transfrom to pose Ctrl+A
        bpy.ops.pose.visual_transform_apply()
        # insert all keyframes -> press I
        bpy.ops.anim.keyframe_insert_menu(type='__ACTIVE__', confirm_success=True) 

def select_all_bones():
    global source, target
    ob = bpy.data.objects[source]
    for bone in ob.pose.bones:
        b=ob.data.bones[bone.name]
        b.select=True
        bpy.context.object.data.bones.active=b
      
ks = bpy.data.scenes["Scene"].keying_sets_all
ks.active = ks['Whole Character'] 

ob = bpy.data.objects[source]
# uncomment line below if you are using Blender version below 2.8 and comment out 2nd line
#bpy.context.scene.objects.active = ob 
bpy.context.view_layer.objects.active = ob
bpy.ops.object.mode_set(mode='POSE')  
#select_all_bones()
add_constraints()
apply_animation()
del_constraints()