A crease is a shared polygon boundary, across which no smoothing is performed.

Poser defines a crease angle for each actor in properties. Edge angles below this angle are considered "smooth" and the renderer will attempt to simulate a continuous smooth surface, instead of a pair of flat polygons, passing through that edge. Edges above the crease angle are considered creases (tight folds) and smoothing doesn't happen.

In a long row of polygons if some are above the crease angle and some below, you'll get mysterious regions of sharp crease followed by no crease, even though to your eye they are nearly identical regions.

The default crease angle is 80 degrees.

Crease/smooth decisions are only made where adjacent polygons are welded by common vertices. If polygons are not welded, their joined edges are merely an illusion and are never smoothed out.

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