Rotoscoping
The technique of manually or semi-automatically tracing mask outlines frame by frame to isolate subjects from their backgrounds. Used as a last resort when automated keying fails.
Rotoscoping is the technique of manually tracing subject outlines using Bezier curves or splines on each frame to generate precise masks (mattes). Originally invented in the 1910s for animation, modern VFX relies on rotoscoping for foreground isolation when chroma key cannot be applied.
Footage shot without green screens, scenes where subject and background colors are similar, or materials with reflections require manual masking for clean separation.
- Shape interpolation: Automatic interpolation between keyframed shapes reduces labor. A typical workflow sets keyframes every 5 frames on 24fps footage
- Hierarchical roto: Separate shapes for body parts (arms, torso, head) follow joint articulation. Per-part management simplifies corrections when limbs overlap
- Edge treatment: Motion blur and hair boundaries require feathering and soft mattes over hard-edged shapes for natural transitions
- AI-assisted roto: Machine learning generates initial masks automatically, allowing artists to focus on refinement. Tools like DaVinci Resolve's
Magic Maskexemplify this trend
Feature films may require rotoscoping on thousands of shots, with dedicated roto artist teams at VFX studios. Work time per shot ranges from hours to days depending on complexity. Despite AI advances, human oversight remains essential for production-quality results.