Basic ray tracing examples?

[AardmanCGI]

Hi,
Does anyone have a really basic example of ray tracing along arbitrary paths in a vray plugin texture? I looked at the dirt shader example but that seems to rely on a Max include (#include "../../../3dsmax_plugins/common/vraydirt_impl.h") to work and I don't have Max.

I am just looking for example code which does something like this (in psudocode):

someData hitValues;
vector rayOrig;
vector rayDir;
bool hit = trace (rayOrig, rayDir, hitValues);

if (hit)
{
vector hit = hitValues.Normal;
float rayDistance = hitValues.rayDist;
}


Could you point me to anything like that?
Thanks,

Philip

[vlado]

I'm attaching the vraydirt_impl.h file here; it does not really contain any 3ds Max specific code. It's somewhat more complicated that what you need, but I hope the main points are clear:

1) You need to create a new ray context out of the existing one using VRayContext::newSpawnContext();
2) You need to fill in the ray direction etc in the rayparams member of the ray context;
3) Declare an IntersectionData structure to hold the result of the nearest hit;
4) Call VRayContext::vray->findIntersection() to get the nearest hit;
5) Do whatever you need with the intersection;
6) Potentially call findIntersection() again to find the rest of the hits along the ray;
7) Release the ray context using VRayContext::releaseContext().

If you need to trace multiple rays for the same shading point, it will be faster to reuse the same ray context, rather than creating a new one from scratch for each ray.

Best regards,
Vlado

[AardmanCGI]

Thanks again for a quick reply. That's really helpful.
One more question - how do I test code changes for material/texture plugins in maya? I seem to have to restart Maya everytime I make a code change otherwise Maya crashes. Is there a way to refresh the plugin to test code changes as I am working on a plugin?
Thanks

[t.petrov]

If you won't need to change any parameters on your shader/texture you can export a vrscene file and then you can use the V-Ray Standalone, which is quite a lot faster in regards to startup and debugging.

There is some documentation how to export a vrscene file: http://www.spot3d.com/vray/help/maya...translator.htm

[vlado]

You could also try unloading and reloading the V-Ray for Maya plugin itself - it should cause all the V-Ray plugins to be reloaded on the next render.

Best regards,
Vlado

[AardmanCGI]

Great, I'll try that. Thanks!