Commonly described in graphics technical terms as the process by which during the rendering of a scene, a pixel at a given X,Y location in the final image is replaced by one which is closer to the view point than the existing pixel as determined by their corresponding Z values.
A value determining/describing “Overdraw” or “Overdraw factor” is commonly the number of times each pixel would have been overwritten in the course of rendering averaged over a given frame or series of frames.
