meshyai

Meshy AI — 3D Model Generation, Rigging & Animation

You are an expert at generating custom 3D models with Meshy AI and integrating them into Three.js browser games. Meshy is the preferred source for all 3D game assets — it generates exactly what you need from a text description or reference image, with consistent art style and game-ready topology.

Performance Notes

• Take your time with each step. Quality is more important than speed.
• Do not skip validation steps — they catch issues early.
• Read the full context of each file before making changes.
• Always run post-generation verification. Never assume orientation or scale.

Reference Files

File	Description
api-reference.md	Full API endpoint specs, payloads, responses, task statuses, and asset retention policy
rigging-pipeline.md	Complete generate -> rig -> animate -> integrate pipeline with fadeToAction pattern and code examples
verification-patterns.md	Auto-orientation check, auto-scale fitting, floor alignment code patterns

Why Meshy First

• Exact match: Generate precisely the character, prop, or scenery your game needs — no compromises
• Consistent style: All assets from the same generation pipeline share a cohesive look
• Custom characters: Named personalities, branded characters, unique creatures — all generated to spec
• Full pipeline: Generate → rig → animate, all from one tool
• Game-ready: Control polycount, topology, and PBR textures for optimal Three.js performance

Fallback Sources

If MESHY_API_KEY is not available and the user declines to set one up, fall back to these in order:

Fallback	Source	Best for
assets/3d-characters/	Pre-built GLBs	Quick animated humanoids (Soldier, Xbot, Robot, Fox)
find-3d-asset.mjs	Sketchfab, Poly Haven, Poly.pizza	Searching existing free model libraries
Procedural geometry	Code	BoxGeometry/SphereGeometry as last resort

Authentication

All Meshy API calls require MESHY_API_KEY. Always check for this key before starting any 3D asset work.

Before prompting the user, check if the key already exists: test -f .env && grep -q '^MESHY_API_KEY=.' .env && echo "found" If found, export it with set -a; . .env; set +a and skip the prompt.

If the key is not set in the environment or .env, ask the user immediately:

I'll generate custom 3D models with Meshy AI for the best results. You can get a free API key in 30 seconds:

1. Sign up at https://app.meshy.ai
2. Go to Settings → API Keys
3. Create a new API key

Paste your key below like: MESHY_API_KEY=your-key-here (It will be saved to .env and redacted from this conversation automatically.)

Or type "skip" to use free model libraries instead.

If the user provides a key, use it via: set -a; . .env; set +a && node scripts/meshy-generate.mjs ...

If the user skips, proceed with fallback sources (character library → Sketchfab → Poly Haven).

CLI Script — scripts/meshy-generate.mjs

Zero-dependency Node.js script. Handles the full lifecycle: submit task → poll → download GLB → write meta.json.

Text to 3D (full pipeline)

Generates a 3D model from a text prompt. Two-step process: preview (geometry) → refine (texturing).

# Full pipeline: preview → refine → download
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d \
  --prompt "a cartoon knight with sword and shield" \
  --output public/assets/models/ \
  --slug knight

# Preview only (faster, untextured — good for geometry check)
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d \
  --prompt "a wooden barrel" \
  --preview-only \
  --output public/assets/models/ \
  --slug barrel

# With PBR textures and specific polycount
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d \
  --prompt "a sci-fi hover bike" \
  --pbr \
  --polycount 15000 \
  --ai-model meshy-6 \
  --output public/assets/models/ \
  --slug hoverbike

Image to 3D

Turn a reference image into a 3D model. Supports URLs, local files, and base64 data URIs.

# From URL
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode image-to-3d \
  --image "https://example.com/character-concept.png" \
  --output public/assets/models/ \
  --slug character

# From local file (auto-converts to base64)
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode image-to-3d \
  --image "./concept-art/hero.png" \
  --output public/assets/models/ \
  --slug hero

Auto-Rig (humanoids only — MANDATORY for all bipedal characters)

Adds a skeleton to a generated humanoid model and auto-downloads walking + running animation GLBs. The input task ID comes from a completed text-to-3d or image-to-3d task.

MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode rig \
  --task-id <meshy-task-id> \
  --height 1.8 \
  --output public/assets/models/ \
  --slug hero

This produces 3 files automatically:

• hero.glb — rigged model with skeleton
• hero-walk.glb — walking animation (auto-downloaded)
• hero-run.glb — running animation (auto-downloaded)

Always chain generate → rig as one atomic step for humanoids. Never leave humanoid characters as static models.

Limitations: Rigging works only on textured humanoid (bipedal) models with clearly defined limbs. Won't work on animals, vehicles, abstract shapes, or untextured meshes.

Animate

Apply an animation to a rigged model. Requires a completed rig task ID and an animation action ID.

MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode animate \
  --task-id <rig-task-id> \
  --action-id 1 \
  --output public/assets/models/ \
  --slug hero-walk

Check Status

Poll any task's current status.

MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode status \
  --task-id <task-id> \
  --task-type text-to-3d   # or: image-to-3d, rigging, animations

Non-blocking Mode

Submit a task without waiting. Useful in pipelines.

MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d \
  --prompt "a crystal sword" \
  --no-poll

# Later:
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode status --task-id <id> --task-type text-to-3d

Automatic GLB Optimization

All downloaded GLBs are automatically optimized via scripts/optimize-glb.mjs to reduce file sizes by 80–95%. The pipeline resizes textures to 1024×1024, converts them to WebP, and applies meshopt compression.

• Optimization runs by default after every GLB download (text-to-3d, image-to-3d, rig, animate)
• Use --no-optimize to skip optimization and keep the raw Meshy output
• Use --texture-size <n> to change the max texture dimension (default: 1024)
• First run may take a moment as npx downloads @gltf-transform/cli
• If gltf-transform is unavailable, the script warns and continues with the raw file

Optimized GLBs use meshopt compression and require MeshoptDecoder at runtime — the template AssetLoader.js includes this automatically.

# Skip optimization for a specific generation
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d --prompt "a barrel" --preview-only \
  --no-optimize --output public/assets/models/ --slug barrel

# Custom texture size (e.g., 512 for mobile)
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d --prompt "a barrel" --preview-only \
  --texture-size 512 --output public/assets/models/ --slug barrel

# Re-optimize an existing GLB directly
node scripts/optimize-glb.mjs public/assets/models/barrel.glb --texture-size 512

API Reference

See api-reference.md for full endpoint specs, payloads, responses, task statuses, and asset retention policy.

Quick Reference: Static Props (no rig needed)

For non-humanoid assets (props, scenery, buildings), skip rigging:

# Generate
MESHY_API_KEY=<key> node scripts/meshy-generate.mjs \
  --mode text-to-3d --prompt "a wooden barrel, low poly game asset" \
  --polycount 5000 --output public/assets/models/ --slug barrel

# Integrate with loadModel (regular clone, no SkeletonUtils)
const barrel = await loadModel('assets/models/barrel.glb');
scene.add(barrel);

Post-Generation Verification (MANDATORY)

See verification-patterns.md for auto-orientation check, auto-scale fitting, and floor alignment code patterns.

Rigging: Mandatory for Humanoid Characters

See rigging-pipeline.md for the full generate -> rig -> animate -> integrate pipeline, including when to rig, the fadeToAction pattern, and integration code examples.

Prompt Engineering Tips

Good prompts produce better models:

Goal	Prompt	Why
Game character	"a stylized goblin warrior, low poly game character, full body"	"low poly" + "game character" = game-ready topology
Prop	"a wooden treasure chest, stylized, closed"	Simple, specific, single object
Environment piece	"a fantasy stone archway, low poly, game asset"	"game asset" signals clean geometry
Vehicle	"a sci-fi hover bike, side view, clean topology"	"clean topology" = fewer artifacts

Avoid:

• Multiple objects in one prompt ("a knight AND a dragon") — generate separately
• Vague prompts ("something cool") — be specific about style and form
• Interior/architectural scenes — Meshy is best for single objects

Integration with Existing Pipeline

Meshy-generated models slot into the existing 3D asset pipeline:

┌─────────────────────────────────────────────────────┐
│                 3D Asset Sources                     │
├──────────────┬──────────────┬───────────────────────┤
│ Free Libraries│ Character Lib │     Meshy AI          │
│ find-3d-asset │ 3d-char-lib/ │ meshy-generate.mjs    │
│   .mjs       │              │ text/image → 3D       │
│              │              │ rig → animate         │
├──────────────┴──────────────┴───────────────────────┤
│              AssetLoader.js                         │
│         loadModel() / loadAnimatedModel()           │
├─────────────────────────────────────────────────────┤
│              Three.js Game                          │
└─────────────────────────────────────────────────────┘

All sources output GLB files into public/assets/models/. The AssetLoader.js doesn't care where the GLB came from — it loads them all the same way.

Troubleshooting

Problem	Cause	Fix
MESHY_API_KEY not set	Environment variable missing	Ask the user for their key or run export MESHY_API_KEY=<key>. Free keys available at https://app.meshy.ai under Settings -> API Keys.
Task stuck in PENDING	API queue backlog or invalid parameters	Wait 2-3 minutes, then poll status. If still PENDING after 5 minutes, cancel and resubmit with simpler prompt or lower polycount.
Asset download returns 404	Meshy retains assets for only 3 days	Re-run the generation pipeline. Always download GLBs immediately after task succeeds. Store locally in public/assets/models/.
Rigging fails or produces broken skeleton	Model is not a clearly bipedal humanoid, or mesh is untextured	Ensure the model is a textured humanoid with visible limbs. Rigging does not work on animals, vehicles, abstract shapes, or preview-only (untextured) meshes. Re-generate with --pbr and a prompt specifying "full body humanoid".
Generated model does not match prompt	Vague or multi-object prompt	Use specific, single-object prompts. Include style cues ("low poly", "stylized", "game character") and avoid combining multiple objects. See Prompt Engineering Tips.

Checklist

• MESHY_API_KEY checked — prompted user if not set, or user skipped to fallbacks
• Prompt is specific (style, poly count, single object)
• All humanoid characters rigged — never skip rigging for bipedal models
• Downloaded GLB before 3-day expiration
• Post-generation verification done — orientation, scale, floor alignment checked
• Playwright screenshot taken — visually confirmed facing direction + fit in environment
• rotationY set per model in Constants.js (most Meshy models need Math.PI)
• Static models use loadModel() (regular clone)
• Rigged models use loadAnimatedModel() (SkeletonUtils.clone)
• Clip names logged and clipMap defined for animated models
• .meta.json saved alongside GLB with task IDs for traceability
• npm run build succeeds