Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/SummerEngine/summer-engine-agentnpx agentmods add skills/summerengine/summer-engine-agent/procedural-animationWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/summerengine/summer-engine-agent/procedural-animation)<a href="https://agentmods.dev/skills/summerengine/summer-engine-agent/procedural-animation"><img src="https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/procedural-animation/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/summerengine/summer-engine-agent/procedural-animation"><img src="https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/procedural-animation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00093 | $0.03912 |
| Opus 5 | $0.00046 | $0.01956 |
| Sonnet 5 | $0.00019 | $0.00782 |
| Haiku 4.5 | $0.00009 | $0.00391 |
Grade A, and why
procedural-animation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 253 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Procedural Animation — Bones Driven by Code
Generated clips give you 80% of a character. The remaining 20% — the eye contact when an NPC speaks, feet that plant on slopes, hands that wrap a sword grip, the lean into a sprint, the recoil from a hit on the left shoulder — is procedural. In Summer Engine this is done via the SkeletonModifier3D family attached to the Skeleton3D, plus tween-driven additive blend layers on the AnimationTree. None of it is generative; this skill is a recipe set.
Honest limit: Summer Engine's current IK is good enough for look-at, foot-snap, and simple two-bone arm/leg chains. It is not a full-body IK system with weight redistribution. For combat-grappling or contact-heavy interactions, hand-author the contact frame and accept some clipping.
When to use this skill
- Feet clip into / float over uneven terrain.
- NPC head doesn't track the player during conversation — feels dead-eyed.
- Character's hand doesn't actually hold the sword — pen-through.
- Body doesn't lean into turns / aiming.
- Hit reactions need to come from the hit direction (recoil left when struck left), not just one canned animation.
- Ragdoll on death.
When NOT to use this skill
- The clip already covers it. Don't IK what mocap already nailed — adds CPU cost and rounding error.
- The character is far from the camera (LOD2+). Procedural cost outpaces visual benefit. Disable modifiers past 15m.
- You need facial animation. That's
summer:animation/facial-and-lipsync. - You haven't generated base clips yet. Skeleton modifiers compose ON TOP of clips; without a base pose they'll stack on T-pose and look wrong.
The three patterns
Almost every procedural request maps to one of these three. Pick the right one before writing code.
Pattern A — SkeletonModifier3D (post-clip bone overrides)
Attached as a child of Skeleton3D. Runs after the AnimationTree writes the pose, modifies specific bones in-place. Includes LookAtModifier3D, SkeletonIK3D (legacy, still supported), and the new (4.4+) LookAtModifier3D chain. Cheap, deterministic, no animation graph dependency.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 253 lines · 93 tokens per session scan A 2b94c0bef59a
procedural-animation is a skill published in the GitHub repository SummerEngine/summer-engine-agent (59 stars, last pushed today), licensed MIT. It adds 93 tokens to every session and 3,912 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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