# ray tracer: shooting ray

## Recommended Posts

takis    150
Hello, I have implemented arcball into my raytracer. The arcball works perfectly.
glPushMatrix();
glMultMatrixf(m_pArcBall->getrotationmatrix().ptr());
m_pDocument->draw();
glPopMatrix();

For my raytracer, do i have to recalculate my viewposition en viewdirection if i am using my arcball? Can i recalculate it like this: viewpos=m_pArcBall->getrotationmatrix()*viewpos; viewdir=m_pArcBall->getrotationmatrix()*viewdir; where eye=viewpos and center=viewpos+viewdir

##### Share on other sites
takis    150
I just want to know if i rotate an object with arcball. Do i have to change the eye of the camera in order to shoot rays to the object?

How can i extract the eye and the center from the model_view matrix?

[code]
void ArcBall::mouseMove(float mouseX, float mouseY, float viewW, float viewH)
{
// map [0, w] to [-1, 1] and [0, h] to [-1, 1]
float x=2*mouseX/viewW-1.0f;
float y=2*((viewH-mouseY)/viewH)-1.0f;

Vector3D vTo=mapToSphere(x,y);

m_qDrag.setFromPoints(m_vFrom,vTo);
m_qNow.product(m_qDrag,m_qDown);

Quaternion q=m_qNow;
q.conjugate();

m_mTrans=q.getRotationMatrix();
}
[\code]

##### Share on other sites
Max_Payne    757
I will try to answer, but I'm afraid you aren't being clear enough. Could you specify what you call an "arcball", and precisely what it is you're trying to do?

When you rotate the camera, you necessarily have to emit the rays in a different direction, because it rotates the image plane around the camera's origin. You just have to rotate the corners of this image rectangle around, and use that to interpolate the pixel positions.