Forward Shadow Mapping

Forward shadow mapping is a new approach to real-time shadow generation. The traditional shadow map algorithm maps the pixels in the eye's view backward into the depth buffers of light sources (i.e. shadow maps), which is similiar to and often implemented as an extension to texture mapping. Our algorithm reverses this process by using 3-D image warping techniques to transform shadow map pixels forward into the eye's view to directly indicate which pixels are lit; it does not interfere with normal texture mapping and easily supports anti-aliased shadow edges and projective textures.  Access to shadow maps and projective textures is in pixel-sequential order. This algorithm has advantages when speed of texture mapping becomes the performance bottleneck, which is often the case in visual simulation and game applications.
Forward Shadow Mapping, Hansong Zhang, Rendering Techniques '98, Proceedings of the 9th EuroGraphics Rendering Workshop, Vienna, Austria, June 29-July 1, 1998, Drettakis, G., Max, N. (eds.) ISBN 3-211-83213-0 (Postscript. Figures: 2 4a 2 4b 5a 6 )

This figures illustrates the shaodow generation pipeline for one implementation of forward shadow mapping which supports projective textures and anti-aliased shadow edges. The final image as well as intermediate images are shown.
512x512 final images using a 512x512 shadow map. The projective texture is the same as the one in the pineline figure (spotlight with grid pattern). The modulation buffer is blurred for the left image and not blurred for the right. You have to click on the images for larger versions to better see the difference.
512x512 final images using a 256x256 shadow map. The modulation buffer is blurred for the left image and not blurred for the right.
This image is taken from a interactive demo of walking robot in a spotlight. 

Back to Hansong's home page.