This is an idea I had.
Let's start by peeking at a simplified pipeline -
First, we render the Viewed From Light Shadow Maps that will contain the Z from the depth buffer. So far, as usual for shadow mapping.
Next, comes the first pass that is part of my idea. It executes a pixel shader, because we need the Zbuffer.
Shadow Map is sampled here for the first pass of the Path Tracing. It is explained why, later.
“Hit x,y,z” has simply the visible part of the projected geometry. Instead of saving the color, it saves …