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Raytraced shadows
Monday, August 30, 2004 | Permalink

Executable
Source code
RaytracedShadows.zip (949 KB)

Required:
GL_ARB_shader_objects
GL_ARB_vertex_shader
GL_ARB_fragment_shader
GL_ARB_shading_language_100
This demo shows how to generate shadows through raytracing. This is easy enough to do with simple object such as spheres, which this demo uses. Shooting a ray through a list of spheres requires few computations. In fact, assuming the GLSL compiler generates optimal code it will only need 5 instructions per sphere, and then we're getting soft shadows for free. The limit is instead on the number of interpolators, which limits the number of spheres to 7 on current hardware, unless of course you go multipass (which would be straightforward).

Press the left mouse button to kick balls around. The longer you hold the button, the stronger the kick. It will kick in the direction you're looking.

This demo should run on Radeon 9500 and up and GeForce FX 5200 and up.

2004-08-31: The demo should now work properly on nVidia cards too.