Computing Camera Rays: A Robust Alternative to Rasterization
As real-time rendering shifts toward full ray tracing, calculating camera rays directly from view-projection matrices becomes essential. I explain why the standard method of subtracting near and far plane points causes catastrophic numerical cancellation, leading to jittery visuals. Instead, I present a more reliable approach that works seamlessly for both perspective and orthographic projections without needing custom code for every camera model.
I strongly advise against using the obvious strategy of computing ray direction by subtracting points on the far and near planes, as it causes catastrophic cancellation that turns smooth camera motion into a jittery mess.