Soft area shadows from a single shadow map

I knew you could create soft shadows from mulitple shadow maps and doing some averaging to blend them into a single soft shadow. But I didnt know you could do it with only a single shadow map. But Bertrand Bry-Marfing found a way and put the shader up on his site:

http://www.3db-site.com/html/renderman_shaders.php


So now I've been able to compile the shader and use it in maya with 3delight. I was going to try for something like this after I got the occlusion stuff to work but since he had the shader already I figured I could give it a go. It also works with deep shadowmaps !