---
title: "Identity and first frames"
description: "Two different jobs that an input image can do, and how to tell roasOS which one you want."
url: https://docs.roasos.com/concepts/identity-and-first-frames
---

# Identity and first frames

An image that you attach to a request can do two very different jobs. Give the image the correct role, or the result is wrong.

* **Identity.** "This is the person. Keep this face and this body in every shot." roasOS sends the image to the model as a character reference.
* **First frame.** "The video starts on this exact picture." The model animates the picture that you gave.

A third role is close to both, and it is neither:

* **Style reference.** "Make it look like this." The model copies the light, the colour and the material. It does not copy the person.

## The fields

| Job         | Fields                                 |
| ----------- | -------------------------------------- |
| Identity    | `avatar_id`, `elements`                |
| First frame | `image_url`, `scene_id`, `scene_image` |
| Last frame  | `end_image_url`                        |
| Style       | `references`                           |

Each model page gives the roles that the model accepts, in its **Media** section. [Nano Banana Pro](/models/image/nano-banana-pro) is an example. A role that the model does not accept gets `400 unsupported_option`.

## Choose the correct one

<Steps>
  <Step>
    ### The same person must appear in many shots

    Use identity. Create an avatar once, then send `avatar_id` on each request. Avatar creation generates its [character reference sheet](/concepts/character-reference-sheets) automatically: an original full-body image followed by a matching three-panel sheet. roasOS resolves the saved identity into the references supported by the selected model.

    <Callout type="warn">
      `avatar_id` names a roasOS gallery avatar or an avatar that your workspace already holds. Create one through `POST /v1/avatar/nano-banana-pro` or in the app. The plural resource route `POST /v1/avatars` is not a creation endpoint. `GET /v1/avatars`, `GET /v1/avatars/{id}` and `DELETE /v1/avatars/{id}` manage saved avatars.
    </Callout>

    `POST /v1/avatar/nano-banana-pro` creates an original full-body image, then generates a three-panel sheet from that image and derives its individual crops. The sheet is included in the avatar creation quote; no separate purchase or enrichment step is required.
  </Step>

  <Step>
    ### You have the exact opening picture of the clip

    Use the first frame. Send `image_url`, or send `scene_id` when the picture is a scene that roasOS made.
  </Step>

  <Step>
    ### You want the look, not the person

    Use `references`. Do not put a face in `references` and expect the face to stay the same.
  </Step>
</Steps>

## Rules to remember

* **A first frame carries its own identity.** If the first frame already shows the correct person, do not send an identity field too. The UGC family works this way: the scene is the first frame, and the person in the scene is the person in the clip.
* **Some models refuse a face.** Seedance 2.5 takes reference media, and the provider's own likeness filter refuses a human face in it. It refuses a real face and a generated face. The run then fails with `provider_rejects_face_references`, and roasOS refunds the reservation. Use Kling 4.0 when the person must stay the same. Refer to [Seedance 2.5](/models/video/seedance-2.5) and to [Kling 4.0](/models/video/kling-4).
* **A real person needs a consent record on some lanes.** A voice clone, an avatar lipsync and a recast onto an uploaded face each take a versioned attestation. Refer to [Media rights](/concepts/media-rights).
* **Do not describe the role in the prompt.** Write what the person does and where the product is. roasOS writes the placement text.
* **Do not describe the face.** The identity image does that job. A written face description fights the reference.

## From an image to a video

The usual sequence has three steps.

1. Make the still with [Nano Banana Pro](/models/image/nano-banana-pro), with `avatar_id` for the person and `product_id` for the product.
2. Send the result URL as `image_url` to a video model.
3. Poll the job and read the result. Refer to [Jobs](/concepts/jobs).

Step 2 works because a result is an immutable object on `https://cdn.roasos.com`. Refer to [Reference media and uploads](/concepts/reference-media).

One workflow does the same three steps for you, on one door: [Animate a still](/workflows/animate-a-still).

## Next

* The shots behind `product_id`: [Product kits](/concepts/product-kits).
* Put a different person in a finished clip: [Recast an actor](/workflows/recast-an-actor).
* Whose face you may send: [Media rights](/concepts/media-rights).