ray casting

I want to know any basic code written already for the ray casting for the Volumetric data.
Any help/suggestions/links please.

Volumetric data I would imagine is as a 256x256x256 grid, in which case if you look at any ray tracing book you will see that raytracing grids is very common. It is used as an acceleration technique, the scene is divided into sections and objects within a grid block are stored. Here each voxel will be an object and if the ray hits a grid block with a voxel then you have just hit the volumentric data.

So look up grid based accelerations, and take a look at www.raytracingnews.org

Neil Witcomb