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ReC98/libs/sprite16/sprite16.inc

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[Reverse-engineering] [th03] SPRITE16 calls Aha! TH03's in-game graphics run in line-doubled 640×200 simply because that's what this SPRITE16.COM version was written for, making use of the PC-98 EGC for optimized blitting. Doesn't seem all *too* optimized though, given that it chooses to effectively draw every sprite twice, just in case it might overlap with something that's already in VRAM. It first clears the previous VRAM content at the drawing position according to the sprite's alpha mask, then ORs in the actual sprite data. The EGC can do monochrome alpha- tested blitting just as well as the GRCG, but once the sprite data covers all bitplanes, ORing is apparently the best it can do by itself? More technical details on the raster operations in the next push! Completes P0056, funded by rosenrose and [Anonymous].
2019-11-03 11:47:10 +00:00
; Function numbers for the SPRITE16.COM driver, according to SPRITE16.DOC.
; Only includes functions that are actually used in TH03.
SPRITE16 = 42h
SPRITE16_GENERATE_ALPHA = 1
SPRITE16_PUT = 2
SPRITE16_SET_MONO = 3
SPRITE16_SET_COLOR = 4
SPRITE16_SET_OVERLAP = 5
SPRITE16_SET_MASK = 8
OVERLAP_CLEAR = 1
OVERLAP_OR = 0