Module sky 

Sky-texture resource for the textured-sky startsky path.

Mirror of voxlap’s skypic / skylng[] / skylat[] / skybpl / skyxsiz / skyysiz / skylngmul globals (voxlap5.c:220- 234). Built once when a host calls Engine::set_sky; the per-frame search state (sky_curlng / sky_curdir / sky_off) lives on ScanScratch and gets reset before each frame’s opticast.

Voxlap loads the sky from a .png (loadsky), then builds two lookup tables:

• lng[y] for y in 0..ysiz: (cos, sin) of the row’s latitude angle. Drives the per-ray search in gline’s frustum prep.
• lat[x] for x in 0..xsiz: packed (xoff << 16) | (-yoff & 0xffff) where xoff = cos(...)·32767, yoff = sin(...)·32767. Used by phase_startsky to find the texel column for each pixel ray.

After table init, voxlap decrements xsiz by one (“skyxsiz–; //Hack for assembly code”, voxlap5.c:3968). The lat[] table still has original_xsiz entries; the search starts from index xsiz (= post-decrement value, originally an out-of-range index, used as the initial edi cursor).

Structs

Sky

Sky texture + precomputed angle-lookup tables.