I wrote a quick and dirty computer program a while ago that generates a 5pt perspective grid.
It's quite simple, just start with a big circle (which is the horizon if you look straight down into the ground and have 180degree vision), then draw centered ovals horizontally and vertically, and in the middle you draw radiating lines which works as the forward VP.
It sorta works, but the trouble is spacing the ovals, cuz the density should increase towards infinity the less oval they get, ie. the closer to the edge of vision they are. I don't know by what formula...
There's a perspective grid near the bottom here but I think it has the same problem as mine, the squares get distorted near the edges.
Jamen jag tror att han skäms, och har gömt sig. Vårt universum det är en av dom otaliga spermasatser som Herren i sin självhärliga ensamhet har runkat fram för å besudla intet.