Hi

I have written a simple CPU raytracer which just generated this image:

I just realized that I am calculating the secondary rays origin incorrectly. I was simply adding a random number to the x and y of the origin point. This is fine when my lookat point is at the same height at my camera position but if it is higher or lower, my square aperture will be tilted. How do I find a random point in the aperture rectangle around my camera?

Some code:

//primary ray

Ray newRay = camera.GetRay(x, y, HEIGHT, WIDTH, antiX, antiY);

//convergent point on focal plane

Vec3 focalPoint = newRay.calculate(camera.focalLength);

            double origX = randOrigin(generator);

            double origY = randOrigin(generator);

            Vec3 randomOrigin(newRay.origin.x + origX, newRay.origin.y + origY, newRay.origin.z);

            //direction to focal plane

            Vec3 focalDir(focalPoint - randomOrigin);

            focalDir = focalDir.normalized();

            newRay = Ray(randomOrigin, focalDir);

Thanks

If I understand the problem correctly, you need to know which direction is "left and right" and "up and down" relative to your "focalDir" vector, correct?  You could calculate this with a few cross products, but you need to throw in another point of reference, usually an "up" vector (in this case, i'm assuming the Y vector is "up")

    zAxis = vectorMinusVector(target, camPos); //this is your current focalDir
    zAxis.vectorNormalize();
    xAxis = vectorCrossProduct(up, zAxis);
    xAxis.vectorNormalize();
    yAxis = vectorCrossProduct(zAxis, xAxis);
    vectorNormalize(yAxis);

    //now you have you an xAxis and yAxis to move around on
    pos.addVector( vectorTimesFloat(xAxis, randomX) );
    pos.addVector( vectorTimesFloat(yAxis, randomY) );

Another option would be to use the camera matrix instead of generating all new vectors.  Then all of these vectors are sorta bundled together in a neat package, and you can just do local translations, but the results would be the same.