Ray setup in CUDA using OpenGL-supplied matrices

I'm working on a project where I port my CUDA code for usage as a module in a big application which maintains its own OpenGL state. My module basically is a volume renderer. I am now facing the problem that I have to setup the rays of the volume renderer to exactly mimic the开发者_运维知识库 OpenGL camera, so that my volume renderering fits with the rest of the rendered scene.

At the point where my CUDA code is called there is a viewing matrix (no model-view matrix) and a projection matrix set. I already extracted the frustum parameters and the camera position in world space.

u *= -c_pp.right;
v *= -c_pp.top;

Ray eyeRay;
eyeRay.o = make_float3(c_camPosition); //origin
eyeRay.d = normalize(make_float3(u, v, -c_pp.near)); //direction

u and v are normalized screen coordinates running from -1 to 1. c_pp describes the view frustum using top, right and near. I'm now looking for the appropriate matrix I have to multiply with so that eyeRay.d shows in the right direction. So far using the viewing matrix or its transposed or inverted version failed.

Update:

Changed u *= -c_pp.right to u *= c_pp.right and everything works by multiplying eyeRay.d with the inverse viewing matrix.

Complete fixed code:

u *= c_pp.right;
v *= -c_pp.top;

Ray eyeRay;
eyeRay.o = make_float3(c_camPosition); //origin
eyeRay.d = make_float3(u, v, -c_pp.near)); //direction
eyeRay.d = mul(c_invViewMatrix, eyeRay.d);

with c_inViewMatrix being the inverse view matrix.

This question has been answered by the original poster inline. The answer is to change u *= -c_pp.right to u *= c_pp.right (sign change). See above.

I've added this answer to reduce the number of unanswered questions in the CUDA tag to help make it more useful.