# Act-One (Runway)

**Source:** https://promtable.com/glossary/act-one

> Act-One is Runway's performance-capture feature that takes a webcam recording of a person's face and retargets the performance onto a generated character — making AI-generated characters convincingly act.

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Act-One is Runway's performance-capture feature that takes a webcam recording of a person's face and retargets the performance onto a generated character — making AI-generated characters convincingly act.

Launched by Runway in late 2024, Act-One was the first widely-used AI tool that solved character performance capture without motion-capture rigs. The user records a short video of themselves performing the lines + expressions, supplies a character reference image, and Act-One generates a clip of the character performing the same way. Quality is good enough for narrative work, ads, and short films. By 2026 Act-One has become a standard tool in AI-assisted filmmaking workflows alongside Gen-4. Major limitation: extreme angles and overlapping faces still struggle.

## When to use

- AI-assisted filmmaking and animation.
- Ads requiring character dialogue.
- Performance capture without mocap rigs.

## Common mistakes

- Trying to retarget faces with extreme rotation — degrades quickly.
- Cropping too tight — Act-One needs context to retarget convincingly.

## Related terms

- [diffusion-model](https://promtable.com/glossary/diffusion-model)
- [voice-cloning](https://promtable.com/glossary/voice-cloning)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/act-one
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