How The Girl Who Cried Pearls tracked CG mouth replacements with invisible UV ink

befores & afters' technical deep dive (2026-01-06, building on its 2025-11-24 overview) reports how The Girl Who Cried Pearls (Chris Lavis & Maciek Szczerbowski, National Film Board of Canada) solved CG mouth-replacement tracking without altering its stop-motion puppets. Directors refused the VFX team's usual asks -- cutting away a puppet's nose and ears, shrinking its head, or adding visible tracking markers. Technical director Eric Pouliot tested highlighters and glow-in-the-dark paint, both of which failed on the puppets' porous latex skin, before landing on the OPTICZ Invisible Ink Pen, a UV-reactive marker built for security document marking. Marked in invisible ink, the puppets were then shot with Dragonframe's multi-exposure feature paired to a DMX-automated UV light: one exposure per frame for the final beauty image, one under UV to reveal the tracking dots, both frame-locked automatically. The technique -- folded into the wiki at UV-ink tracking for CG face replacement -- is catalogued here as a third path for puppet dialogue animation alongside continuous resculpting and physical replacement-face inventories: the CG mouth is composited on afterward, tracked from marks the camera could see but the audience never could.