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Modfy Agent Skeleton

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Tyler Britton2
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I have an agent primitive that I want to modify the skeleton of. Modifying the skeleton is easy, but I am trying to find a way to update an existing agent primitive with the new modified skeleton. Is there a way to do this?

If not, and I have to create a new agent primitive through something like an Agent From Rig sop, can I copy the motion clips from an existing agent to my newly created agent?
Edited by Tyler Britton2 - Feb. 18, 2025 18:23:33
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tony_a
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I think you'll need to create a new agent if you want to change the rig. You may need to re-do your skin weighting as well.

As for the motion clips, you should be able to re-target them to your new rig: https://www.youtube.com/watch?v=B4RT4OLu5E8 [www.youtube.com]

I think it depends on how drastic of a change you're making to your rig though, they may just work.
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cwhite
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In a Python SOP you can also use `hou.AgentDefinition.freeze(new_rig=...)` to make a new agent definition with a different rig (copying the clips etc to reference the new rig).
But, like the previous post suggests, if you're changing joint names you'll have limited success and would need to re-target the motion instead
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Tyler Britton2
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Thank you for the help.

The joints are all the same, so luckily, I don't need to do any retargeting.
I made a python script that will go through the input agents, and hopefully swaps the skeleton out for the one from the second input. It successfully swaps the rigs, however the skeleton doesn't seem to be swapped, it is still the one from the first input.

Any help is appreciated. 

node = hou.pwd()
input_geo = node.geometry()  # This is the writable geometry in a Python SOP
reference_geo = node.inputs()[1].geometry()  # Second input (read-only)

# Get reference agent from second input
if len(reference_geo.prims()) > 0:
    reference_agent = reference_geo.prims()[0]
    reference_def = reference_agent.definition()
    reference_rig = reference_def.rig()
    reference_shape_lib = reference_def.shapeLibrary()
    print(f"Reference rig found: {reference_rig}")
    print(f"Reference definition: {reference_def}")
    print(f"Reference shape library: {reference_shape_lib}")
else:
    print("Error: No agent in reference input (second input)")
    raise hou.NodeError("No agent in reference input")

# Process each agent in the input geometry
for i, agent in enumerate(input_geo.prims()):
    print(f"\n--- Agent #{i} ---")
    
    # Get original definition and info
    original_def = agent.definition()
    print(f"Original definition: {original_def}")
    print(f"Original rig: {original_def.rig()}")
    print(f"Original clips: {len(original_def.clips())}")
    print(f"Original layers: {len(original_def.layers())}")
    print(f"Original transform groups: {len(original_def.transformGroups())}")
    
    # Create a new frozen definition with the reference rig
    new_def = original_def.freeze(new_rig=reference_rig)
    print(f"New definition created: {new_def}")
    print(f"New rig: {new_def.rig()}")
    print(f"Clips preserved: {len(new_def.clips())}")
    print(f"Layers preserved: {len(new_def.layers())}")
    print(f"Transform groups preserved: {len(new_def.transformGroups())}")
    
    # Update the agent's definition in place
    # In a Python SOP, node.geometry() is directly modifiable
    agent.setDefinition(new_def)
    
    # Verify the change
    print(f"Updated agent: {agent}")
    print(f"New agent definition: {agent.definition()}")
    print(f"New agent rig: {agent.definition().rig()}")


Reference rig found: <hou.AgentRig rig:new_agent>
Reference definition: <hou.AgentDefinition 0x0000773c34602100>
Reference shape library: None

--- Agent #0 ---
Original definition: <hou.AgentDefinition 0x000077400e9f9780>
Original rig: <hou.AgentRig rig:agent1>
Original clips: 18
Original layers: 65
Original transform groups: 7
New definition created: <hou.AgentDefinition 0x0000773c3f3aeb00>
New rig: <hou.AgentRig rig:new_agent>
Clips preserved: 18
Layers preserved: 65
Transform groups preserved: 7
Updated agent: <hou.Agent prim #0 of geometry frozen at 0x773ff5d23c00>
New agent definition: <hou.AgentDefinition 0x0000773c3f3aeb00>
New agent rig: <hou.AgentRig rig:new_agent>
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