n Commonly described in graphics technical terms as the process by which during the rendering of a scene, a pixel at a given x-axis|X,y-axis|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-axis|Z values.
n 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.