With industrial design drawings, we're taught to use contour lines to convey an object's form. Most of you already know what I mean, but laypeople, look at the sketches above (courtesy of ID Sketching, by the way). Obviously the lines you see bisecting the camera lenses, and the centerlines on the car and the objects in the bottom sketch are not meant to appear on the finished product, but they quickly help your eye detect contour and volume.
A research team at Japan's AIST (Advanced Industrial Science & Technology) has cleverly exploited this idea and applied it towards motion-capture and measuring applications. What they've done is designed a grid pattern comprised of wavy lines, then used a projector to cast it onto whatever's being scanned. After recording the proceedings with a high-speed camera, software then examines the grid, frame-by-frame; by observing the way each line breaks, the software can calculate the volume.
See it in action: