blog/skills/concept-art-pipeline.md

# Skill: Concept Art Pipeline

End-to-end workflow for creating game character art --- from design brief through 2D concept art to 3D model export. This skill covers everything before the game engine.

## Overview

| Phase | What | Output |
|-------|------|--------|
| 1 --- Design | 2D concept art via AI image generation | Approved PNG(s) |
| 2 --- Model | 3D generation via Tripo Studio | GLB/FBX export |
| 3 --- Handoff | Reference file for the dev team | Markdown spec |

## Phase 1: 2D Concept Art

### Locking Your Art Style

Before generating anything, define your art style once and enforce it everywhere. Write it down. Here's an example for a stylised game:

- **Stylised 3D render**, anime-influenced but not full anime
- **Matte skin**, no metallic sheen, warm earthy tones
- **Neutral confident expression** --- calm determination, not fierce or smiling
- **Earthy palette**: browns, tans, dark reds, cream, black
- **Asymmetric accessories** --- different on left vs right
- **Dark grey background** for all concept art (consistent, easy to composite)

### Hard Rules (define yours)

Every project should have a "do not" list. Examples:

- NO Disney-adjacent designs (if you're going for something grittier)
- NO overly shiny or metallic materials (unless your game's style calls for it)
- NO hair falling forward over chest (won't animate well in-engine)
- NO culturally inappropriate elements (research your references)

### Cultural Direction

If your game draws from real cultures, create an approved/rejected table:

| Approved | Rejected |
|----------|----------|
| Woven natural fibres, shell jewelry | Generic "tribal" patterns |
| Specific cultural motifs (research them) | Stereotypical elements from wrong cultures |
| Natural materials (bone, wood, stone) | Modern materials that break the setting |

### Generation Steps

1. **Get the brief** --- gender, role, distinctive features, or "surprise me within the style"
2. **Generate 3 variants** using your image generation tool (see [Image Generation skill](image-generation.md))
   - T-pose, front view, consistent background
   - Naming convention: `character_<name>_front_full_v01.png`
3. **Score each variant** using a rubric (see below)
4. **Generate reference sheet** for the winner --- front, side, three-quarter, head closeup
5. **Save with metadata** --- prompt, model used, date, score

### Scoring Rubric (0--10)

| Score | Meaning | Action |
|-------|---------|--------|
| 9-10 | Perfect match to art style and brief | Approve, generate reference sheet |
| 8 | Strong, minor tweaks needed | Approve with notes, iterate once |
| 6-7 | Interesting but needs changes | Note what works, regenerate |
| 4-5 | Wrong direction, some salvageable elements | Extract what works, fresh prompt |
| 0-3 | Off-target | Drop, adjust approach |

**Score on:** style match, cultural accuracy, expression, silhouette (distinctive at distance?), technical (T-pose clean? animatable?)

### Layered Design

Design characters in separable layers for future equipment/customisation:

1. **Base body** --- simple underwear, no accessories
2. **Lower garment** --- baked into character mesh
3. **Upper garment** --- baked or swappable
4. **Hair** --- separate asset (swappable)
5. **Accessories** --- equipment slots (necklaces, bracelets, headwear)
6. **Cape/cloak** --- separate equipment piece

Generate the full character for the overall look, but keep separation in mind for 3D.

## Phase 2: 3D Model Generation

### Using Tripo Studio

[Tripo Studio](https://studio.tripo3d.ai) generates 3D models from text or images.

1. Open Tripo Studio
2. Text-to-3D or paste your approved concept art for image-to-3D
3. Use **Ultra quality**, latest model version, **Texture ON** (~35-50 credits)
4. Export as **GLB** (preferred --- preserves PBR textures) or FBX
5. Save to your project's asset pipeline

Tripo outputs ~1.5M faces with full PBR textures (basecolour, normal, ORM). You'll decimate to your target polygon budget in Blender or your engine.

### Large Hair Problem

Auto-riggers (like Mixamo) break when the mesh includes big hair --- wrong arm poses, face distortion, rig artifacts.

**Rule:** For characters with large or complex hair:
- Export a **body-only version** (no hair) for rigging
- In Tripo: use **Segment** to split hair from body, export body-only
- Hair is added back as a separate mesh after rigging

### Polygon Budget

Define your LOD targets. Example:

| LOD | Face Count | Use |
|-----|-----------|-----|
| LOD0 | 25,000 | Close-up, player character |
| LOD1 | 10,000 | Medium distance NPCs |
| LOD2 | 2,500 | Crowd/background characters |

### Texture QA Checklist

Before handoff, verify:

- [ ] PBR textures present --- basecolour, normal, roughness/metallic maps
- [ ] No UV seams on prominent areas (face, hands)
- [ ] Skin tone matches the approved concept art
- [ ] No texture stretching on limbs or torso
- [ ] Accessories have distinct materials
- [ ] Resolution 2K minimum for hero characters
- [ ] No generation artifacts (floating geometry, merged fingers, extra limbs)

## Handoff

Create a handoff document for each approved character:

1. **Character identity** --- name, role, description
2. **Concept art files** --- paths to approved PNGs
3. **3D model files** --- path to GLB/FBX exports
4. **Art direction notes** --- what to keep, what to change
5. **Technical requirements** --- shader, rig type, LOD targets, scale
6. **Known issues** --- large hair flag, texture problems, etc.

## Batch Generation

When generating multiple characters:

1. Prepare all briefs upfront
2. Generate in priority order (ship-soonest first)
3. Use free retries before spending credits
4. Score as you go --- don't batch review
5. Track credits per generation
6. Export immediately after approval (don't leave work in the cloud tool)

## Common Mistakes

| Problem | Cause | Fix |
|---------|-------|-----|
| Characters look generic | No art style lock | Define and enforce your style guide |
| Inconsistent across characters | No reference images | Use your best character as image-to-image reference |
| Metallic skin sheen | Default material settings | Use matte keywords, check PBR roughness |
| Symmetric accessories | Generation default | Explicitly describe left vs right in prompt |
| Auto-rigger fails | Large hair in mesh | Segment and export body-only |
| Low-poly look in engine | PBR textures missing | Always generate with Texture ON + PBR ON |

## Related Skills

- [Image Generation](image-generation.md) --- fal.ai Flux models and prompt patterns
- [Tripo 3D](tripo-browser-workflow.md) --- detailed Tripo Studio workflow
- [Sora 2 Video](sora2-video.md) --- animate concept art into video