I never found an explanation for delta polygons. How are they made? the actual hline drawing must be more or less the same basic idea? The line routine I made years ago used mask tables and a unrolled loop inbetween that I moved the PC to the correct place for the current line. I never found any documentation on it, but it seemd to be the easiest way to do it.
One thing I thought about was a way to make sure you don't draw polygons on top of each other if you have many polygons on the screen at once. First sort the polygons so they are drawn FRONT to back, then calc the first polygon and create a table with left and right values for all hline spans, then instead of drawing them, just save the table and start with the next polygon. If the coordinates for a line span in that polygon is between the ones that are currently in the table, then clip if it's partially hidden or ignore it.
After all polygons are calculated you have a buffer with info about all line spans on the screen. Maybe something like: color,start_x,end_x,color,end_x,color,end_x
the previous line's end coordinate would be the next ones start coord.
It sounds like it could be a fast way to draw polygons if you have the entire screen filled or maybe it would still be to much so you don't gain anything usefull in framrate
Atleast I guess you could save the tables for every frame and then draw all spans like in an animation
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