# AI3D API v2 model: tripo-retopology

Retopologize or decimate an existing 3D model with Tripo's mesh decimate endpoint.

- AI3D model ID: `tripo-retopology` (native Tripo API, `mesh/decimate`)
- Task: `model_to_model`
- Provider adapter: `tripo`
- Default provider model version: `v2.0` (smart retopology); `v1.0` is basic decimation
- Availability: listed in `GET /v2/models` only once Tripo operations are enabled on the deployment. Until then `POST /v2/jobs` returns `400 unknown model`.
- Provider reference: <https://developers.tripo3d.ai/en/docs/mesh-decimate>

Create a normal prepaid AI3D job. Do not call Tripo directly or put a provider key in a client.

```http
POST https://api.ai3d.dev/v2/jobs
Authorization: Bearer <AI3D_API_KEY>
Content-Type: application/json
Idempotency-Key: <unique-request-id>
```

```json
{
  "model": "tripo-retopology",
  "source_job_id": "3f6c0e2e-6a3f-4f1e-9d0c-1b2a3c4d5e6f",
  "input": {
    "face_limit": 5000,
    "quad": false
  }
}
```

Source model: send exactly one of these top-level fields. Do not put them inside `input`.

- `source_job_id`: the UUID of your own completed Tripo job (`tripo-h31-image`, `tripo-h31-text`, `tripo-p1-image`, `tripo-p1-text`, or `tripo-p1-multiview`).
- `model_url`: a public HTTPS link to a GLB, GLTF, FBX, OBJ, or STL file (up to 150 MB at Tripo). AI3D does not fetch it; Tripo does. URL input is not verified for this operation; prefer `source_job_id`.

Jobs created by Fal-hosted Tripo models or any other provider cannot be used as `source_job_id` and return 422. Use `model_url` instead; for a public GLB or GLTF job you can pass its public viewer artifact URL.

Optional `input` settings: `model` (`v2.0` or `v1.0`), `face_limit` (required), `quad`, and `bake` (v2.0 only; rejected for `v1.0`).

`face_limit` windows:

- `v2.0`: 500 to 20,000 faces, or 500 to 10,000 when `quad` is true.
- `v1.0`: 1 to 2,000,000, or 1 to 150,000 when `quad` is true.

Reserve (an upper bound, in Tripo credits at $0.01 each):

| `model` | Credits | USD |
| --- | --- | --- |
| `v2.0` or omitted | 30 | 0.30 |
| `v1.0` | 10 | 0.10 |

AI3D reserves before dispatch and settles against Tripo's reported credits, never more than the reserve. A job that fails at Tripo is not charged.

Errors: `404` source job not found (also returned for another account's job), `409` source job has not completed successfully, `422` invalid settings or a source job that cannot be used. Failed jobs report `provider_input_invalid`, `provider_request_rejected`, or `provider_insufficient_credits`.

Output: the retopologized model is archived in `artifacts` (usually GLB) together with a preview image. Poll `GET /v2/jobs/{job_id}` until `succeeded`, `failed`, or `submission_unknown`. Use the same idempotency key when safely retrying a timed-out request.