AI 3D Generation for Game Assets: Draft Fast, Commit Slow

One of the biggest surprises building my AI video-story pipeline was how much the when to spend money question dominates 3D work. A single Hunyuan3D generation with PBR costs $0.525. A Trellis draft? Two cents. Get the order wrong and you're burning money on geometry that's wrong from the start.

After a few wasted generations I landed on a hard rule: never run Hunyuan3D on the first attempt. Draft with Trellis first, get shape approval, then commit to the full pipeline.

The Decision Tree

Need a 3D model?
  ├── Draft / concept → Trellis ($0.02) — fast shape check
  │     └── Approved? → Hunyuan3D v3 ($0.525 with PBR) — production GLB
  ├── Need rigging + animation? → Meshy API (subscription)
  └── Text-only input? → Hunyuan3D text-to-3D (skip Trellis)

The key insight is that Trellis and Hunyuan3D are solving different problems. Trellis gives you a rough shape bake in seconds — good enough to catch a bad silhouette or a topology problem before you commit real money. Hunyuan3D gives you a production-quality GLB with PBR channels (Base Color, Metallic/Roughness, Normal, AO) that can go straight into a game engine.

Tool Comparison

That Replicate number is not a typo. Trellis on fal.ai costs $0.02. The same model hosted on Replicate costs $0.82. Always check which platform is hosting the model before you run anything.

Stage 1 — Trellis Draft

Trellis runs via the fal.ai Python SDK. A minimal draft script:

import fal_client, os, time

result = fal_client.run(
    "fal-ai/trellis",
    arguments={"image_url": image_url}
)
glb_url = result["model_url"]

The output is a .glb with baked flat colour — no PBR, no normal map. That's fine for the draft stage. You're checking shape, proportions, and whether the model reads well from the camera angles you plan to use.

Total turnaround: about 30–60 seconds. Cost: $0.02.

Stage 2 — Hunyuan3D Final

Only run after the draft shape is approved:

result = fal_client.run(
    "fal-ai/hunyuan3d-v3/image-to-3d",
    arguments={
        "input_image_url": image_url,
        "enable_pbr": True,      # +$0.15 — always worth it for finals
        "face_count": 500000,
        "generate_type": "Normal",
    }
)
glb_url = result["model_urls"]["glb"]["url"]
# also available: ["obj"], ["fbx"], ["usdz"]

With enable_pbr: True the total is $0.525. You can push it to $0.825 by adding multiview input and a higher face count, but that's only worth it for hero assets. For background props, base + PBR is enough.

The Meshy Pipeline (Rigging + Animation)

For game assets that need to move, Meshy's REST API gives you the full pipeline: image → 3D → remesh → rig → animate. The credit costs stack up:

On the Pro plan ($12/mo, ~100 gens) each generation is around $0.12–0.36. At the Max plan ($45/mo, ~1,000 gens) it drops to about $0.045 per generation — much more economical if you're running a full game art pipeline.

The workflow is async (Meshy queues tasks), so the script polls for completion:

task_id = meshy_client.create_3d_task(image_url)
while meshy_client.get_task(task_id)["status"] != "SUCCEEDED":
    time.sleep(5)
glb_url = meshy_client.get_task(task_id)["model_url"]

GLB Analysis — Know Before You Ship

Before any model goes into a game engine, I run a GLB audit:

python3 ~/.claude/skills/glb-analyzer/generate.py /path/to/model.glb

This generates a self-contained model_analysis.html with an embedded Three.js viewer and a full PBR channel report. No server required — just open the file.

The thresholds I use:

Spaceship Test — Real Numbers

My first real test was a spaceship concept generated from a fal.ai image. Results after a Trellis draft:

• File size: 1.36 MB
• Geometry: 1 mesh, 9,572 triangles, 6,584 vertices
• PBR: none (Trellis only bakes flat colour)
• Verdict: PC game-ready (< 15k tris) ✅

The shape was clean enough that I'd approve it for Hunyuan3D if the project called for a production version. Total cost to validate: $0.02.

The Rule That Saves Money

The pipeline only works if you enforce the draft gate. It's tempting to skip Trellis when you have a clean reference image and high confidence — but even a $0.375 miss stings more than a few cents of validation. Draft first, commit once.

For static assets going into cutscenes: Trellis → Hunyuan3D + PBR.
For game characters that need to walk: Trellis → Meshy full pipeline.
For background props where rigging doesn't matter: Trellis → Hunyuan3D base (no PBR, save $0.15).

The two-cent draft is the cheapest design review you'll ever run.