model in a 2D space. The two main types of projection are orthographic projection (also called parallel) and perspective projection. The main characteristic of an orthographic projection is that parallel lines remain parallel after the transformation. Perspective projection utilizes the concept that if the distance between the observer and model increases, the model appears smaller than before. Essentially, perspective projection mimics human sight. Clipping Clipping is the process of removing primitives that are outside of the view box in order to facilitate the rasterizer stage. Once those primitives are removed, the primitives that remain will be drawn into new triangles that reach the next stage. Screen mapping The purpose of screen mapping is to find out the coordinates of the primitives during the clipping stage. Rasterizer stage The rasterizer stage applies color and turns the graphic elements into pixels or picture elements. See also Bounding interval hierarchy Demoscene Geometry instancing Optical feedback Quartz Composer Real time (media) Real-time raytracing Video art Video display controller References Bibliography External links RTR Portal – a trimmed-down "best of" set of links to resources Computer graphics Computer graphics