Hand tracking v9 — Smear
Fingertips become brushes loaded with the camera's own pixels, smearing colour only where they travel; at rest the path can rewind and unpaint itself.
The camera image itself never shows: instead the hand drags rounded daubs of it across a black canvas, so skin, sky and shadow appear only where fingers have travelled. The live hand rides on top as a thin rainbow outline, marking where the brush currently is.
Each tracked point samples the hidden source frame — webcam, clip or still — at its own position and stamps a coloured disc, interpolating extra stamps along fast moves so strokes never break up. The stamps live in one ordered list, which enables a rewind mode: once the hand rests long enough, daubs peel off the newest end and the painting retraces itself stroke by stroke.
