If a flat illustrated character turns into a live-action or strongly three-dimensional figure during AI video, check rendering consistency separately from identity. A recognizable face can survive while the medium changes. The starting thumbnail may be correct even though highlights, skin texture, or volumetric shading gradually replace the intended drawing style.
Define what makes the design two-dimensional
Do not rely only on the word cartoon. Name the visible rules in the approved still: a particular outline weight, flat color areas, a small number of shadow tones, simplified facial marks, and the absence of photographic surface detail. Specify which of these are deliberate design decisions rather than artifacts you hope the model will clean up.
Runway's image-to-video guidance explains that the input image supplies composition and style while the prompt describes motion and temporal progression. That is useful guidance for its model, not a guarantee that any video system will preserve every drawing rule. The acceptance card below remains a human review method, including when you use another video service.
Make a rendering lock card
| Feature | Approved rule | Failure to inspect |
|---|---|---|
| Outline | Clean, consistent illustrated contour | Lines fade into realistic edges |
| Color | Deliberate flat areas | Unrequested skin or fabric texture |
| Shading | Limited graphic shadow shapes | Continuous glossy volume |
| Face | Simplified approved marks | Photographic eyes, pores or lips |
| Motion | Readable drawn performance | Medium changes during turns |
Use the actual design's rules, not every row by default. A painted character may legitimately have texture and soft volume. The purpose is to preserve that character's chosen medium, not force all illustration into the same flat style.
Start with a motion you can inspect
For a first check, choose a modest action such as a head turn with a small hand gesture, if it suits the project. A fast full-body spin can expose unapproved back views and make a rendering failure harder to distinguish from a design gap. Reduce those uncertainties before combining complex performance and camera movement.
A hypothetical brief is: “The approved illustrated character turns slightly toward the viewer and raises one hand. Keep the same clean contour, flat painted color areas and graphic shadow shapes throughout the movement. The camera holds a readable medium view.” This is an authored planning example, not a tested universal prompt or a command that guarantees style preservation.
Inspect the transition, not just the poster frame
Check the opening, the largest change in angle or gesture, and the ending. Also play the transitions between them. A single middle still can miss a brief switch to realistic eyes or a glossy face that appears only during movement. Record identity, drawing medium, and action completion as separate decisions.
For an Imagild recreation, assign each reference its purpose and avoid letting a live-action motion reference silently become the rendering authority. If the medium changes, reject that pass even when the action is attractive. Return to an approved still, narrow the action, or revise the role description before spending on a longer sequence that would multiply the same problem.