Imported from simon0191/a-los-traques (.claude/skills/generate-poses/SKILL.md). Install upstream with npx skills add simon0191/a-los-traques --skill generate-poses. Copyright stays with the author.

Generate Pose Keypoints

End-to-end pipeline for extracting per-frame pose keypoints from a fighter's sprite animations. Writes one poses.json per fighter, colocated with the sprite strips, describing head/hand/foot positions plus derived orientation angles. Consumed at runtime to attach visual elements (hats, weapons, effects) to body parts with correct rotation.

When to use

Run this after a fighter's sprites have been fully generated and had their facing direction corrected via /generate-fighter. Don't run it before Phase 4 of that skill — the post-hoc -flop fixes will swap left* and right* keypoints across animations and invalidate every derived angle.

Prerequisites

• assets/manifests/poses_{id}.json exists. If not, copy poses_simon.json and change output + fighter.
• All 13 animation PNG strips exist at public/assets/fighters/{id}/{anim}.png. Check with ls public/assets/fighters/{id}/.
• uv is on the PATH. First invocation installs MediaPipe + OpenCV into an isolated cache under scripts/asset-pipeline/pose/.venv.
• ImageMagick (magick) is on the PATH — same dependency as the fighter pipeline.

Workflow

1. Smoke-test with debug previews

Run the pipeline with --debug so skeleton overlays are written to assets/_raw/poses/{id}/{anim}_debug.png:

node scripts/asset-pipeline/cli.js poses assets/manifests/poses_{id}.json --debug

First run downloads MediaPipe model weights (~30 MB) and can take up to a minute. Subsequent runs complete in ~10s for all 13 animations.

The pipeline prints a per-animation summary at the end. Example:

  - simon/idle: 4/4 frames detected
  - simon/block: 1/2 frames detected (review debug strip)
  - simon/knockdown: 2/4 frames detected (review debug strip)

Partial detection in block, hurt, and knockdown is expected — the character's pose is ambiguous (arms over face, body horizontal) and the affected frames are stored as detected: false.

2. Review debug strips

Open the debug strips for three representative animations and show them to the user:

open assets/_raw/poses/{id}/idle_debug.png
open assets/_raw/poses/{id}/light_punch_debug.png
open assets/_raw/poses/{id}/knockdown_debug.png

Ask: "Does the skeleton track the character's actual body — head on head, wrists on wrists?"

• If yes, proceed.
• If the skeleton is consistently mirrored (left/right swapped) across a whole animation, that usually means Phase 4 of /generate-fighter wasn't run for that animation. Confirm with the user and re-run the fighter pipeline's facing fixes before regenerating poses.
• If detection is wrong only for specific frames inside block/hurt/knockdown, leave as-is — these are marked detected: false and runtime code should skip attachment for those frames.

3. Verify JSON output

Confirm the output file exists and has all 13 animations:

jq '.animations | keys' public/assets/fighters/{id}/poses.json

Sanity-check a derived block for a character standing upright and facing right:

jq '.animations.idle.frames[0].derived' public/assets/fighters/{id}/poses.json

Expect head.roll near 0 and torso.angle near 90. Large deviations on the very first idle frame usually indicate a detection problem worth investigating.

4. Commit

Stage the manifest (if new) and the generated JSON:

git add assets/manifests/poses_{id}.json public/assets/fighters/{id}/poses.json

The assets/_raw/poses/{id}/ directory holds intermediate frame splits and debug previews — it's regeneratable and should not be committed.

Output shape

One JSON file per fighter, colocated with sprites:

public/assets/fighters/{id}/poses.json

Top-level fields: version, fighter, frameSize (128), model, generatedAt, animations.

Each animation has frameCount and a frames array. Each frame has:

• index, detected, avgVisibility
• keypoints — 23 named landmarks as {x, y, v}. Coordinates are pixel-space relative to the 128×128 frame, top-left origin, y down (matches Phaser sprite-child coords).
• derived — head {center, roll, yaw, pitch}, torso {center, angle}, {left,right}Hand {anchor, angle}, {left,right}Foot {anchor, angle}. Angles are degrees, counter-clockwise from +x axis. Phaser rotates clockwise, so renderer code must negate.

When detected: false, both keypoints and derived are null.

Key lessons

• Run after /generate-fighter Phase 4. Facing fixes (magick -flop) happen post-hoc and swap left/right semantics. Run poses before that, and the JSON is wrong.
• Transparent backgrounds break pose models. detect.py composites each RGBA frame over mid-gray (128,128,128) before inference. Never composite over green — some sprites have green flames that would bleed.
• static_image_mode=True is required so MediaPipe doesn't try to track state across unrelated animations.
• model_complexity=2 (heavy) is more tolerant of limbs at the frame edge (common in heavy_kick, special). Still <2 minutes total for 800 frames.
• Cached frame splits in assets/_raw/poses/{id}/{anim}/frame_*.png are reused across runs. Delete the directory to force re-split if a sprite strip changed.
• poses.json is consolidated per fighter — one file holds all 13 animations. Regenerating a single animation rewrites the whole file.