486quake.exe: Fast ("blob") model renderer broken?

[maikmerten]

Hello there,

this is comparing 486quake.exe and 586quake.exe from https://github.com/goshhhy/486quake/releases/tag/1.09-r8

To speed up model rendering, Quake will render only a coarse approximation of "far away" models. IIRC, it'll just emit a suitably colored pixel per triangle instead of "properly" rasterizing the triangle as usual (I think this is called the "blob" renderer).

With 486quake.exe, it appears that pixels are missing or misplaced, making the models somewhat appear like a "see through" pixel cloud, instead of solid objects:

486quake.mp4

With 586quake.exe, the approximate model rendering appears to work fine (just like WinQuake):

586quake.mp4

Another obvious place to test this is with the two patrolling grunts at the entrance of the base - as they walk away from the observer, in 486quake.exe they disintegrate a fair bit, becoming partially see-through.

As is obvious from the screen captures, I'm testing this in Dosbox-X. I didn't yet have the opportunity to test on actual hardware.