Alternative method of camera control
gluLookAt computes and applies an appropriate translation & rotation
gluLookAt(cameraX, cameraY, cameraZ,
lookX, lookY, lookZ,
upX, upY, upZ)
cameraX, cameraY, cameraZ is camera location - point to look from
lookX, lookY, lookZ is point to look at
upX, upY, upZ is "up-direction" for the camera - affects camera roll