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Guide · AI video

How to keep characters consistent in AI video

Ask an AI video tool for the same character twice and you often get two different people: another face, another age, another coat. Consistency doesn't come from a better prompt alone — it comes from fixing what the character looks like once and reusing exactly that, every shot.

Why characters drift

Each generation starts from noise and your words. A description like “a tall woman in her thirties with dark hair” fits thousands of faces, so every shot picks a different one. Lighting, style words and camera terms that change from prompt to prompt make it worse: the same person looks different in a different visual language.

What actually keeps them the same

  1. Write one definitive description per character — face, age, build, hair, clothing, distinguishing marks — taken from the book, not improvised per shot.
  2. Make and approve one reference image per character (and per location) from that description.
  3. Register the reference in the tool once: a persistent character (Soul ID in Higgsfield, “elements” or reference images in Kling, Runway, Veo and others).
  4. Use one style line for the whole project — palette, lighting, lens, era — and paste it into every prompt unchanged.
  5. Use one negative line too, for what must never appear.
  6. For each shot, attach the references of everyone in it and describe only what changes: action, framing, emotion.

Locations and objects

The same rules apply to places and to objects that matter to the story — a house, a weapon, a letter. If a viewer would notice it changing, it needs a reference and a fixed description.

Limits to know

  • No tool imports a whole project: you upload references and paste prompts shot by shot.
  • Tools differ in how many references a shot accepts, and some refuse reference images with realistic faces.
  • Long sequences still need a human eye: check each clip against the reference before keeping it.

Where CAINIX fits

CAINIX does the preparation from your book: a Visual Bible with the definitive look of every character and location, image descriptions and reference images you approve, and then the Generator Pack — one ZIP with a prompt and an approved reference for every character and place, a printable sheet per character, the project's single style line and negative line, and, once the screenplay or series is written, a ready prompt per scene with the dialogue and the files to attach. It works with Higgsfield, Kling, Runway, Seedance, Veo and others.

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