A Look at Pathfinder

The float texture containing the masks for our simple scene might look something like this:

It is very common when dealing with vector graphics to separate the computation of coverage (whether a pixel is in or out of the path) shading (color of the pixel if it is covered). In pathfinder, the edge quads are equivalent to groups of vertical rays coming from the top of the tile, writing the contribution of a single edge to all pixels below the edge, down to the bottom of the tile. Rather than only writing the winding number between edges, pathfinder simply writes the contribution of each edge to all pixels below it, which will give the same result since the contribution of two edges can cancel each other out if our imaginary ray was going in then out of the path before reaching the pixel.

Source: nical.github.io