Method and apparatus for shadow generation through depth mapping

Abstract

A method and apparatus for creating shadowed scenes for interactive image generation. Shadowing is effected by generation of a shadowing coefficient for each pixel, which is then used when the scene is rendered. The present invention utilizes z-buffer and projective texture mapping facilities of an image generation system. Generation of the shadow coefficient is achieved by the steps of: rendering the scene from the viewpoint of a light source using z-buffering to create a two dimensional depth map from said z-buffer; storing the depth map in texture mapping storage; rendering the scene from the viewpoint of the viewer; for every pixel in view creating an index info said depth map and a iterated depth value; retrieving a predetermined number of depth map samples from the depth map based on the position of a depth map index; comparing said iterated depth value with each of the depth map samples to determine which of the depth map samples are in shadow; creating a weighted average shadow coefficient from the results of the comparisons; and using the shadow coefficient for rendering. Optionally, the values in the depth map are offset by an amount dependent on the slope of the distance function relative to the depth map indices. The scene is then rendered utilizing surfaces and/or shading information. The shadow coefficient is used to calculate the pixel intensity thus creating realistic shadow effect.