motion

Motion Generation Skills

How an agent turns a character mesh into a usable animated FBX — and how to judge whether the result is shippable.

Motion assets are a special category: many clip / mesh / engine formats, per-character skeletons, and unit conventions that static-mesh QA does not cover. Prefer the gen_motion operator first; when a format or retarget edge case is outside what the operator already handles, the agent may edit the retarget code (<REPO_PATH>/operators/gen_motion/funcs/retarget_utils/ and related steps) rather than inventing a one-off workaround outside the pipeline.

This skill covers the whole motion chain in 3AGameFactory:

character mesh (.glb/.obj/…)
        │
        ▼
   rig  (Puppeteer)          →  rig.txt + skeleton.txt + mesh.obj
        │
        ▼
   motion (MoMask | Mixamo | …) →  motion.bvh / source.fbx
        │
        ▼
   retarget (world-delta)    →  retargeted.fbx + animation.fbx + mapping.json
        │
        ▼
   import (Blender / UE5)    →  engine-ready skeletal asset

Entry point: <REPO_PATH>/pipeline/assets_gen/gen_motion/run.py. Operator: <REPO_PATH>/operators/gen_motion/operator.py. Code the agent should read before changing anything: this file, then the module docstrings under <REPO_PATH>/operators/gen_motion/funcs/.

Get the clip by download first

Text-to-motion generation quality and controllability are not good enough yet. MoMask produces a plausible-looking clip from a sentence, but you cannot reliably control timing, style, exact limb trajectories, foot contact, or how the clip loops — and re-prompting rarely converges on what the plan asked for.

So for any real game deliverable, download a clip first and prefer Mixamo:

1. Mixamo — the default source. Broad, consistent, game-oriented humanoid library on one skeleton (mixamorig:*), so SOURCE_SKELETONS already knows it and retargeting is predictable. It is login-gated, so download by hand: FBX Binary, Skin = Without Skin, then use task_type=retarget with motion_source=mixamo and global_scale=0.01 (centimetres).
2. Other libraries — MoCap Online, CMU BVH, or a local clip, per Motion sources. Check each licence; Bandai-Namco is research-only.
3. MoMask text-to-motion — use it when no downloadable clip fits, when the motion is unusual enough that no library has it, or for a quick placeholder while the game is being assembled. Say that it is the generated route, and expect to review it harder.