Volume Rendering in Renderman

[Gravedigger]

not sure if brickmaps are the best way to do this. if you've access to RPS15 you can read closest points in a pointcloud. like this you could do an interpolation and get smooth results. if you don't have RPS15 you'd have to write your own algorithm to find the closest points

how are you reading the brickmaps at the moment? i think you're result is simply wrong

grs
Patrik

[nycsamurai]

I'm raymarching through the volume. This is what the shader looks like. Even with 10000 steps, and a tiny filterradius it looks like crap. If I limit the values (with something like if(density > 0.11 && density < 0.22)) you get the render below. It seems like a typical raymarch. I'm subtracting opacity based on the density value but it seems to do the trick.


volume bkcloud(point position = point(0, 0, 5); float num_steps = 10000;
string filename = ""; color cloud_color = 1;)
{
float len = length(I);
float step_size = len/num_steps;
point In = normalize(I);
point p_cur = P - I;
Oi = 0;
normal N0 = 0;
float depth = 2;
float density = 0;
p_cur = p_cur - (depth * In);

//get initial opacity
// texture3d(filename, p_cur, N0, "nebuladensity", density);
// Oi = density;
Oi = 0;

//march down incident ray
while(len > 0)
{
texture3d(filename, p_cur, N0, "nebuladensity", density,
"filterradius", 0.0001);
//if(density > 0.11 && density < 0.22)
Oi += (1 - Oi) * step_size * density;
Ci += (1 - Oi) * step_size * cloud_color * density;

p_cur += step_size * normalize(I);
len -= step_size;
}

}



http://johnlukasiewicz.com/renderman/nebula_render.png

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