Animated Asset

Animated asset pipeline

Turns a one-line idea ("a cheerful corgi") into a rigged voxel creature with 13 animation clips, exported as glTF. Four stages, each with a QA gate. Run them in order; never skip a gate — a bad early artifact wastes every later stage.

Exactly ONE gate is a manual user pick — present the material, then stop and wait:

1. concept selection (stage 1): the user picks one of four generated concept images.

Every other gate is automated; ask the user only when one fails twice in a row.

Layout

assets//                      (PascalCase name, e.g. Corgi)
  concept/candidate_{1..4}.png      stage 1 candidates + concept_sheet.png + concept.json (CDN urls)
  _mesh.glb                   stage 2: Hunyuan-3D output
  .vox                        stage 3: MagicaVoxel voxels, 5 cm cells, facing -Y
  previews/_vox_{front,side,top}.png
  layout.json, _rules.py      stage 4: derived body plan + voxel->bone rules
  _rigged.blend               stage 4: the rig, all clips stashed in the NLA
  _animated.glb               stage 4: EXPORT — every clip as a glTF animation
  report.json, run.log              guards, timings, everything that was run

Tools live in this repo: tools/pipeline/concept.py, tools/pipeline/run_creature.py, tools/voxelizer/ (build once with CMake), tools/rig/ (Blender scripts + clip modules). Requirements: Blender 5.2 LTS on PATH (or BLENDER=/path), a fal API key (FAL_KEY or ~/.fal/key), Python 3.10+ with Pillow for the contact sheets.

Stage 1 — concept image (fal text-to-image)

Model: bytedance/seedream/v5/pro/text-to-image. Use the fal-ai MCP tools (run_model / submit_job + check_job) when that server is connected; otherwise run

python tools/pipeline/concept.py  --idea "a cheerful corgi" --len-m 0.9 \
       --anatomy "" --colors ""

Prompt rules (the template is in concept.py and [references/fal-generation.md](references/fal-generation.md)): depict the animal AS voxel art ("large chunky visible cubes, MagicaVoxel style, roughly N cubes long"), side three-quarter view, legs clearly separated from each other and the ground, plain light-grey background, whole model in frame. Thin parts (tails, whiskers, antler tines) must be thickened into slabs or omitted — they shred at 5 cm. --len-m is the real-world length; cube counts in the prompt follow from it (1 cube = 10 cm in the prompt, 5 cm in the voxels).

Auto QA first: view each candidate. Reject any that are not blocky axis-aligned cubes, lack a plain background, crop the body, fuse the limbs, or grow thin appendages. Fewer than 2 survivors → regenerate before involving the user.

USER PICK (mandatory): show concept_sheet.png and STOP until they choose. Keep the picked candidate's fal CDN URL — stage 2 takes it directly.

Stage 2 — image to 3D (Hunyuan-3D), Stage 3 — voxelize, Stage 4 — rig + animate

One command runs all three and writes the report:

python tools/pipeline/run_creature.py  --image-url  --len-m 0.9

What it does, and the gates it applies:

• Mesh — fal-ai/hunyuan-3d/v3.1/pro/image-to-3d, generate_type: Normal, PBR on,

face_count: 100000 (plenty for voxels, 4x smaller download). ~2.5 min. If the rear comes out wrong (Hunyuan hallucinates unseen views), pass a back-view image via back_image_url.

• Voxelize — tools/voxelizer cuts the mesh at 5 cm cells (--long-axis = 2 x metres x 10).

Facing is detected from the voxel grid (the taller end is the head) and the yaw is swept automatically. Check previews/_vox_side.png: the head must be at the image LEFT. The heuristic fails on animals whose rump is higher than the head (rhino, boar) or whose tail is raised (skunk); fix those by re-running the voxelizer with --yaw and passing --vox.

• Rig — tools/rig/voxrig.py derives the body plan from the grid (leg zone = bottom layers

still split into separate blobs, tail = narrow trailing slices, head = whatever rises at the front) and writes _rules.py (voxel -> bone). generic_quad_build.py builds a 14-bone quadruped rig with rigid per-bone weights, authors Idle / Walk / Gallop / Graze / Alert, then exec's every module in tools/rig/clips/ (Trot, Jump, Sit, Sleep, Shake, Stretch, LookAround, Rear) and exports the glTF. Gaits are scaled by leg length; the same maths runs on a fox and a hippo.

QA gate (numeric, never visual): report.json → stages.rig.guards. DIRECTION GUARD: OK means every planted foot sweeps tailward and touches the ground in the Walk; suspension: YES means the Gallop has an airborne frame (legs one voxel tall can't — the clip still exports). Every extra clip prints its own EXTRA CLIP : N frames | guard: OK .... Read [references/rigging-traps.md](references/rigging-traps.md) before touching any rig code — it is the accumulated list of things that silently produce wrong animation, including why vision-model judges cannot be trusted to tell a forward walk from a backward one.

Optional: add --video to render a 3/4-view preview MP4 per clip into previews/.

Stage 5 — use it

_animated.glb imports into Godot, Unity, Unreal and three.js with all clips as named animations (Idle, Walk, Gallop, ... same names on every animal, so a state machine can key on them). The .blend keeps the rig editable. (tiny-voxel additionally bakes the clips into its own rigid-part runtime format; that baker is engine-specific and not part of this repo.)

Wrap up

Report one line per stage: model used, voxel dims and count, clips exported, and any gate that needed a retry. Leave the unpicked candidates in concept/ — never delete.

Scope

Quadrupeds only. The rig is one body plan with derived proportions; bipeds, birds, snakes and anything with a moving tail need their own build script. Blocky voxel animals are the easy case for both meshing and weights — nothing here claims organic characters.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: rehan-remade
• Source: rehan-remade/animated-asset-skill
• License: MIT

Install and usage instructions live in the source repository linked above.