Since the Jaguar blitter is very slow, I want to avoid overdraw.

The broken memory controller does not like span buffer. So BeamTree it is (WIP)

For touchpad:

Portals can clip other polygons in 3d => beam . Portals cannot use NDC. Infinite precision does not like NDC because it add another multiplication to all vertices on screen. NDC does help with culling, but lazy precison float clip away the bulk at low precision anyway. Clipping of edges is a bit easier with NDC.

Pixel needs two MUL to shear the x of two vertices to the center. NDC needs one MUL y after clipping. I guess I should store the (x,y) = z * FoV.xy on the 3d vertex. Then for edges add / sub in pixel like in NDC. Each ordinate can be null if the vertex does not have an edge across the respective border. Can nullable be interpreted as the 0th order of lazy precision?

With screen area partition, z is resolved after x,y (I found no good way to aggregate z on a node (minimax belongs to quadtree)). So no clipping or culling can happen. Homogenous coordinates here mean that we use normals in 3d instead of projected 2d vectors. So, internally, there are beams! But this is only the case because I gave up on rounding the screen x,y to digits after a division. Division is deferred. No easy to debug, small values.