Custom Raytracer in COPs

[konstantin magnus]

I wrote a custom render engine in COPs today. While 'engine' is probably a bit far fetched, it's a little ray tracer experimentally supporting:

• Meshes with UV coordinates
• Shading on diffuse textures
• Multiple point lights (including color, intensity, size)
• Area shadows and light attenuation
• Ambient occlusion
• Specular highlights
• Reflections with varying roughness

The snippet basically transforms the pixel canvas to the camera position and shoots rays around using VEX functions like intersect() and primuv().
The rendering process only takes a few seconds. I still have to figure the licensing fees, though

COP_render.hipnc

[Librarian]

thanx fully functional on 16.5

[konstantin magnus]

Here are the single passes for now:

[mestela]

Funny to stumble across this thread a year later, after I'd been struggling to implement it all day. Worse, to realise I had given it a heart already back when it was first posted, so I'd seen it and forgotten about it!

 

[konstantin magnus]

Hi Matt, I can relate to that. The only way to even top this, might be finding your own postings really interesting and new after a few years ; )

[konstantin magnus]

A quick example for raytracing through several layers of texture opacity:

string image_path = chs('image_path');

vector uv = relbbox(0, v@P);
vector4 clr = colormap(image_path, uv);

v@Cd = vector(clr);
f@Alpha = clr[3];

vector pos[];
int prim[];
vector uvw[];
intersect_all(1, v@P, v@N * 1e3, pos, prim, uvw);

vector color_sum = 0.0;
float alpha_sum = 0.0;
foreach(int i; int pr; prim){
    vector color = primuv(1, 'Cd', pr, uvw[i]);
    float alpha = primuv(1, 'Alpha', pr, uvw[i]);
    float mask = alpha * (1.0 - alpha_sum);
    color_sum += color * mask;
    alpha_sum += mask;
    if(alpha_sum >= 1.0) break;
}

v@Cd = color_sum;
f@Alpha = alpha_sum;

 

raytrace_alphas.hiplc

[vinyvince]

Sexy fish @konstantin magnus

Something i have been thinking, is to be able to sample in 3d space all decals or texture bombing stuff so the mesh will inherit the normal from then, and dynamically update build its normal map or eight color from that.. Do you see what i mean @konstantin magnus?

I know i could sample the color and so in point space, but obviously everyone will prefer not to have a very high density mesh to get correct sampling result, so i picture this more on the shader based context... Am i right ?

 

 

 

________________________________________________________________

Vincent Thomas   (VFX and Art since 1998)
Senior Env and Lighting  artist & Houdini generalist & Creative Concepts
 http://fr.linkedin.com/in/vincentthomas

 

[konstantin magnus]

I wrote an article explaining the code for the COPs raytracer a little:

https://procegen.konstantinmagnus.de/custom-raytracer