Roto / Paint Artist

What they do

Roto and paint is the preparation layer everything else is built on. Roto means hand-animating shapes to isolate elements a keyer cannot: an actor shot against a real background who has to sit behind a CG object, hair against a busy street, a hand crossing in front of a screen replacement. The method is articulated: break the subject into separate shapes that match how the body actually bends, shoulder, upper arm, forearm, hand, then set keyframes on the clearest frames and let the shapes carry between them, adding keys wherever the interpolation drifts. Motion blur and partial transparency are the hard parts, and full occlusion is handled with shape lifetimes rather than by fighting the interpolation. Paint means removing what is in the plate and should not be: tracking markers, rigs, wires, safety padding, crew and their reflections, modern signage, a lens flare in the wrong place, or a blemish on a face. Techniques run from tracked clean-plate patches to frame-by-frame hand painting when nothing tracks. Days are long, the work is judged at full size and full speed, and success means nobody ever mentions the shot. It is also the traditional route into a facility, because it teaches plate discipline faster than anything else.

What they decide

The calls that belong to this role and no other.

• How a subject is broken into articulated shapes, which determines whether the roto holds
• Where the keyframes go, and how many a shot needs
• Whether a removal is a tracked clean-plate patch, a projection, or hand-painted per frame
• How much edge softness and motion blur a matte carries
• When a plate cannot be fixed at this stage and needs a different solution (raises it; supervisor decides)

Principles of the craft

• Articulate the shape to the anatomy. Shapes that match real joints deform believably between keys. One big shape around a whole arm will always need a key on every frame, which is how a two-day shot becomes a week.
• Key the clear frames first. Find the frames where the subject is unambiguous, shape those precisely, then work into the ambiguous frames from both sides. Starting at frame one and walking forward guarantees drift.
• The edge carries the believability. Motion blur, hair and semi-transparency are where a matte is judged. A hard-edged matte through a fast movement will read as a cut-out even if the outline is perfect.
• Judge at speed and at size. Roto and paint faults are temporal: chatter, pop, a patch that breathes. They are invisible when scrubbing frame by frame and obvious at twenty-four frames a second on a big screen.
• A tracked patch beats hand painting whenever the plate allows it, because tracked work is temporally stable by construction and hand-painted work has to be made stable by effort.
• Prep quality sets the ceiling for the shot. Every compositor's edge problem downstream is either a plate problem or a matte problem, and the matte is the one that can still be fixed.

Common mistakes

• One shape for a complex subject, which forces a keyframe on every frame and still chatters
• Keying every frame from the start, producing a matte that is technically accurate and visibly unstable
• Ignoring motion blur, so the matte is correct on the still frames and wrong in movement
• Hand-painting something that a planar track would have held steady
• The experienced artist's mistake: perfecting a matte far past what the shot needs, on a matte that is going to be heavily blurred in comp
• Not checking the matte against the actual comp, so effort goes into edges nobody will see

How to learn it

Exercises and routes in, not a reading list.

• Roto a hand crossing frame in a hundred-frame shot twice: once as a single shape and once articulated into fingers, palm and wrist. Time both and compare stability at full speed.
• Take a shot with heavy motion blur and try to make the matte read correctly during the blur. This single exercise is most of what separates competent roto from unusable roto.
• Remove a tracking marker from a moving shot three ways: tracked patch, projection from a clean plate, and frame-by-frame paint. Play all three in a loop and note which one breathes.
• Shoot a plate with an object, then shoot the same plate without it as a clean plate. Do the removal with and without the clean plate. This teaches what to ask for on set.
• Use an assisted roto tool on a shot you have already done by hand. Note where the model's prediction held and where you had to override it, because knowing where to place a correcting key is the skill that survives.