# Vrm Roundtrip CI Gate

> Gate VRM importer/exporter changes using Blender, UniVRM, and VRM4U round-trip metrics. Use when PRs can affect bones, expressions, materials, or animation fidelity.

- Skill: `grtninja/vrm-roundtrip-ci-gate` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add grtninja/vrm-roundtrip-ci-gate`
- Raw SKILL.md: https://api.skillmd.com/api/skills/grtninja/vrm-roundtrip-ci-gate/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: grtninja (https://skillmd.com/u/grtninja)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/grtninja/vrm-roundtrip-ci-gate

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# VRM Roundtrip CI Gate

Use this skill to set up and enforce reproducible VRM round-trip checks.

## Workflow

1. Select canonical fixture VRMs and lock their checksums.
2. Run round-trip stages (Blender -> Unity/UniVRM -> Unreal/VRM4U -> Blender).
3. Compute bucketed deltas for rig, expressions, materials, and animation timing.
4. Enforce thresholds with a deterministic gate script.
5. Fail closed when any bucket exceeds limits.

## Threshold Defaults

- Bone rotation: <= 0.5 degrees per axis
- Bone position: <= 0.001 units
- Blendshape weight delta: <= 0.02
- Name/slot mismatches: immediate fail

## Commands

```bash
python3 scripts/metrics_gate.py \
  --report-json /path/to/roundtrip-report.json \
  --max-rot-deg 0.5 \
  --max-pos 0.001 \
  --max-blend 0.02
```

## References

- `references/roundtrip-buckets.md`
- `references/pin-matrix.md`

## Loopback

If gate fails:

1. Report failing bucket and fixture.
2. Block exporter/runtime promotion.
3. Re-run after targeted fix only.