chore(meta): add asset-gen skill for visual asset generation
Skill for generating CK3-native art assets using the Nano Banana (Gemini 2.5 Flash Image) MCP tool. Includes style guide, category prompt templates, and DDS conversion reference. Encodes learnings from first batch: no circular frames, no vector art, no text, dark backgrounds edge-to-edge, consistent orientation within trait families, max 3 parallel generation calls. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Claude Opus 4.6
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---
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name: asset-gen
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description: >
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Generate themed visual assets for the Lords of Ash CK3 total conversion mod
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using the generate_image MCP tool (Nano Banana / Gemini 2.5 Flash Image).
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Use when generating any mod art: trait icons, modifier icons, decision
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illustrations, event backgrounds, loading screens, bookmark art, coat of arms
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emblems, religion icons, building icons, MaA icons, lifestyle assets, scheme
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icons, focus icons, activity assets, workshop thumbnail, or frontend art.
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Also use when the user asks about visual identity, art direction, asset
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pipeline, or DDS conversion. Triggers on: "generate icons", "make trait art",
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"create loading screen", "asset pipeline", "convert to DDS", "art style",
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"generate assets", "batch generate".
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---
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# Asset Generation — Lords of Ash
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Generate visually consistent, CK3-native art assets using the `generate_image`
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MCP tool.
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Asset descriptions, filenames, resolutions, and directory paths are documented
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in `docs/REQUIRED_ASSETS.md`. This skill provides the visual identity, prompt
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system, and workflow.
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## Prompt Assembly
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Every `generate_image` call uses three parts:
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```
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[STYLE PREFIX] + [CATEGORY TEMPLATE] + [ASSET DESCRIPTION from docs/REQUIRED_ASSETS.md]
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```
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Never call `generate_image` with just the asset description. Always prepend the
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style prefix and matching category template.
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- **Style prefix and color palette**: Read `references/style-guide.md`
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- **Category templates**: Read `references/category-templates.md` and match by
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asset type (trait icon, modifier icon, decision illustration, etc.)
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- **Asset description**: Look up the specific asset in `docs/REQUIRED_ASSETS.md`
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## Aspect Ratio Mapping
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| Asset Type | Pixel Size | `aspect_ratio` |
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|------------|-----------|----------------|
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| All square icons | various | `1:1` |
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| Decision illustrations | 1100x440 | `5:2` (fallback: `16:9` + crop) |
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| Event backgrounds | 1592x848 | `16:9` |
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| Loading screens | 3840x2160 | `16:9` |
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| Bookmark art | 1920x1080 | `16:9` |
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| Frontend art | 3840x2160 | `16:9` |
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| Activity headers | 1100x440 | `5:2` (fallback: `16:9` + crop) |
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| Lifestyle strips | 480x160 | `3:1` (fallback: `16:9` + crop) |
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| Perk tree backgrounds | 348x812 | `9:16` + crop |
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| Lifestyle sidebars | 608x1552 | `9:16` + crop |
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If the tool doesn't support an exact ratio, generate at the nearest standard
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ratio and resize/crop with ImageMagick.
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## Single Asset Workflow
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1. Find the asset in `docs/REQUIRED_ASSETS.md` — note filename, resolution,
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directory, DDS format, and description.
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2. Read `references/style-guide.md` for the style prefix.
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3. Read `references/category-templates.md` for the matching template.
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4. Assemble the full prompt and call `generate_image` with correct `aspect_ratio`.
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5. Save the PNG to `lords_of_ash/` at the correct `gfx/` path.
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6. Report what was generated.
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## Batch Workflow
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When generating multiple assets of the same type:
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1. Read the style prefix and category template once.
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2. Iterate through assets in `docs/REQUIRED_ASSETS.md` for that category.
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3. Use the same style prefix and template for every asset.
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4. Call `generate_image` in batches of **no more than 3 parallel calls** at a
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time. Wait for each batch to complete before starting the next. This avoids
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overwhelming the image generation API.
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5. Save PNGs to correct paths after each batch.
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6. Report summary: count generated, failures, paths written.
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## DDS Conversion
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CK3 requires DDS format. After generating PNGs, convert using the format
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mapping and commands in `references/dds-conversion.md`.
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All output paths are under `lords_of_ash/gfx/`. The full directory structure is
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documented at the end of `docs/REQUIRED_ASSETS.md`.
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## Critical Rules
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- Always prepend the style prefix — without it, images drift in style.
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- Icons need dark/near-black backgrounds — light backgrounds break CK3 UI.
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- Trait icons are 120x120, NOT 60x60. Modifier icons are 60x60.
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- Trait icons MUST be uncompressed ARGB in DDS, not DXT5.
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- CoA emblems MUST be uncompressed ARGB for the color mask system.
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- Modifier icons need mipmaps; trait icons do not.
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- Decision illustrations: weight composition right (left side has UI overlay).
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- Filenames are case-sensitive on Linux — match mod code exactly.
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- Append "absolutely no text, no letters, no words, no labels, no titles, no
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captions, no watermarks" to icon prompts — the model tends to add text despite
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weaker phrasing.
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- Never use circular medallion/coin framing for icons — the model defaults to
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round compositions which leave white/light corners on a square canvas. Enforce
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"flat square, dark background edge-to-edge" in the prompt.
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- Icons must be symbolic motifs only, not scenes or landscapes. If the model
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generates an environment instead of an icon, the prompt needs stronger
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"this is an icon, not a scene" language.
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- Enforce painterly style explicitly — the model sometimes drifts to vector/flat
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graphic/mobile game art. Add "painterly style only — NOT vector art, NOT flat
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graphic design, NOT mobile game art" when this happens.
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- For trait families that form a progression (e.g. weak/strong/savant), describe
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the same base motif in each prompt and only vary the intensity/effects. Specify
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orientation ("horizontal", "not tilted") to keep compositions consistent.
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- Allomantic energy uses cyan-blue, never green or purple.
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## Quality Checklist
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After generating, verify:
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- Colors match the palette (no oversaturated neons, no pastels)
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- Composition matches the category template
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- No unwanted text, labels, or signatures
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- Dark/near-black background for icons
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- Resolution correct (or needs crop/resize)
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- Visually distinguishable from similar assets in same category
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- Ash, mist, or metallic elements present where appropriate
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