It’s not exactly what I was thinking of at first.  I’d imagined some type of ray tracing showing details of cloth texture.  Howver, this demo from Andre Hoyer is infinitely cooler than what I’d first imagined.

“Cloth simulation” simulates the outline of a piece of cloth/fabric dangling on the screen, which you can drag around by various points on the object.  And the “cloth” will react and move and eventually resettle to its original hanging position.  All with realistically generated animations based on physics/gravity, and all computed in real time in JavaScript.  Simply amazing.  This is the sort of thing that wowed the world with applets 14 years ago, and wowed the world again when Flash started to make a big play in the browser a few years later.

HTML5 is coming, and the sorts of things that were reserved for plugins only will be “in browser” and common in the next few years.

“Cloth simulation” demo.