In 1976, Scott Roth created a flip book animation in Bob Sproull's computer graphics course at Caltech using ray tracing with a simple pinhole camera model. The scanned pages are shown as a video on the right. Roth's computer program noted an edge point at a pixel location if the ray intersected a bounded plane different than that of its neighbors. Of course, a ray could intersect multiple planes in space, but only the surface point closest to the camera was noted as visible. The edges are jagged because only a coarse resolution was practical with the computing power of the time-sharing DEC PDP-10 used. The “terminal” was a Tektronix storage-tube display for text and graphics. Attached to the display was a printer which would create an image of the display on thermal paper. (Although a surface normal could have been computed at every ray-surface intersection for grayscale rendering, the pixels of the display were only binary: green or black.) Roth extended the framework, introducing the term "ray casting" in the context of computer graphics and solid modeling.