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Phillip Schuster

Power Render and Volumetric Fog

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Hi !!

does anyone of you has an idea how to do volumetric fog with Power Render. I know about what is done rendering Volumetric Fog (Spherical), but I don't know exactly how to create the Fog-Map. It's done the following way:

Cast a ray for each vertex to the view position and check if this ray intersects a volume sphere. If so, compute the point where the ray gets in the sphere and the second point where the ray leaves the sphere. Then compute the length of the way the ray traveled through the sphere (very easily, you have to points). Then you will need to compute out of that information a number between 0 and 255 (0 is black->no fog, 255 is full fog).
But, that's quite easy to do (ray casting and sphere intersection). But, how do I know where my pixel is in the fog map ????

When I have the fog map, I simply have to render this face again, but with the fog map as the texture and UV-Coordinates set correctely. (In Power Render 3, you can do that Multitexturing, but in Power Render 2.6 you will need to do a second render pass).

Any ideas ??

Phillip

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