chelch5/sprite-pipeline

Sprite Pipeline

Overview

Use this skill for 2D sprite generation and normalization. This workflow is intentionally anchored around one approved frame and a whole-strip generation pass because frame-by-frame generation drifts too easily.

This skill is 2D-specific. If the request is for 3D characters, meshes, or materials, route back through ../game-studio/SKILL.md.

Core Workflow

1. Start from an approved in-game seed frame.
   • The seed frame should already reflect the right silhouette, palette, costume, and proportions.
2. Build a larger transparent reference canvas around that frame.
   • Use ../../scripts/build_sprite_edit_canvas.py.
3. Ask for the full animation strip in one edit request.
   • Do not generate each frame independently unless the user explicitly accepts lower consistency.
4. Normalize the result into fixed-size game frames.
   • Use ../../scripts/normalize_sprite_strip.py.
   • Use one shared scale across the whole strip.
   • Align frames with one shared anchor, typically bottom-center.
5. Optionally lock frame 01 back to the shipped seed frame.
   • Do this when the animation should begin from the exact idle or base pose already in game.
6. Render a preview sheet and inspect the animation in-engine before approving it.
   • Use ../../scripts/render_sprite_preview_sheet.py.

Prompting Rules

Always preserve these invariants in the prompt:

• same character
• same facing direction
• same palette family
• same silhouette family
• same readable face or key features
• same outfit proportions
• transparent background
• exact frame count and slot layout

Always ask for:

• one strip at once
• a transparent canvas
• no scenery, labels, or poster composition
• crisp pixel-art clusters for pixel work
• production asset tone, not concept art

Using Image Generation

For live asset generation or edits, use the installed imagegen skill in this workspace. This skill defines the game-specific process; imagegen handles the API-backed generation or edit execution.

Script Recipes

Create a reference canvas:

python3 scripts/build_sprite_edit_canvas.py \
  --seed output/sprites/idle-01.png \
  --out output/sprites/hurt-edit-canvas.png \
  --frames 4 \
  --slot-size 256 \
  --canvas-size 1024

Normalize a raw strip:

python3 scripts/normalize_sprite_strip.py \
  --input output/sprites/hurt-raw.png \
  --out-dir output/sprites/hurt \
  --frames 4 \
  --frame-size 64 \
  --anchor output/sprites/idle-01.png \
  --lock-frame1

Render a preview sheet:

python3 scripts/render_sprite_preview_sheet.py \
  --frames-dir output/sprites/hurt \
  --out output/sprites/hurt-preview.png \
  --columns 4

Quality Gates

• proportions stay stable across frames
• frame-to-frame size does not drift
• action reads clearly at game scale
• transparency is preserved
• frame 01 matches the shipped sprite when lockback is enabled
• preview looks correct before any in-engine asset index update

References

• Detailed workflow: ../../references/sprite-pipeline.md
• Shared frontend context: ../game-ui-frontend/SKILL.md