5.6Pinning and Letting Go

A pin can hold for the whole shot or only for part of it. With Active only between frames the painted points are free cloth before From; at From the pin takes them where they are, with no jump; after To it lets go and they keep the motion the pin gave them.

For a soft follow, set the Pin's Weight below 1: each painted point is drawn toward the object it follows by a damped spring, so it follows the animation smoothly while the cloth, a Tnpix Volume and collisions still act on it. A fleshy body pinned to its skinned character this way rides the animation, still jiggles and keeps its volume. The Weight is the share of the motion it follows: 0.5 follows half and sags behind, 0.9 about 93 percent; for a region that should hold almost firm, use a Weight near 1.

When the region should follow the character's own animation rather than another object — a cuff on a skinned arm, a collar on a skinned neck — use a Tnpix Preserve instead of a Pin: its painted points sit on the animation below the Solver, whatever was near them at the first frame (see Tnpix Preserve in Chapter 3).

When pinned cloth can tear, Min piece lets small torn pieces fall from the pin, and Reach stops a pin that starts late from pulling back pieces that have already fallen away.

To let a pin go point by point rather than all at once, give it an Active Zone: an Influence Helper over the pinned region, animated to slide off it. Each point is let go as the zone leaves it - a cape peels off the shoulders from one side to the other. With Stays held once touched on, the zone works the other way round: a helper swept over the cloth picks up every point it passes, as a hand gathering cloth would. On a Tnpix Stitch the same zone closes a seam like a zipper: sweep the helper along the seam and it closes behind it.

Tick Invert in the Active Zone group to turn the zone round: the modifier then acts everywhere the zone does not reach. A Pin with Invert and Stays free once touched lets go of every point the helper passes - sweep it along the pinned edge and the cloth peels off behind it. A Stitch with Invert and Stays open once touched unzips a sewn seam the same way, and a Tear with Invert and Stays protected once touched never tears where the helper has been. On Tnpix Forces, Invert keeps the wind out of the zone.