Apple-2-SW/dos33fsprogs
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bubble: more code comments

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This commit is contained in:
Vince Weaver 2024-01-04 12:53:45 -05:00
parent d75f8e43f3
commit a62c101066
1 changed files with 30 additions and 1 deletions
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31
graphics/hgr/bubble/bubble.s
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@ -389,6 +389,22 @@ th_smc:
; "fast" hplot, Xpos in X, Ypos in A
; Apple II hi-res is more-or-less 280x192
; two consecutive pixels on are white
; single pixels are colored based on palette
; we treat things as a monochrome display, on a color
; display odd/even pixels will have different colors
; The Y memory offset is a horrible interleaved mess, so we use
; a lookup table we generated at start. We also add in
; the proper value for page-flipping
; Apple II hi-res is 7 pixels/byte, so we also pre-generate
; div and mod by 7 tables at start and use those
; instead of dividing by 7
; We cheat and don't worry about the X positions larger
; than 256 because our algorithm only goes up to 208
tay ; 2
lda hposn_low,Y ; 4
sta GBASL ; 3
@ -403,6 +419,8 @@ th_smc:
lda mod7_table,X ; 4
tax ; 2
; 31
; get current 7-bit pixel range, OR in to set new pixel
lda (GBASL),Y ; 5
ora log_lookup,X ; 4
sta (GBASL),Y ; 6
@ -454,9 +472,14 @@ flip2:
bit PAGE2
jmp next_frame
;.include "hgr_clear_part.s"
.include "hgr_table.s"
; we could calculate these, or else build them from
; a 0..pi/2 table to save a lot of space
; the alignment was there to potentially save cycles on page
; crossing. Maybe not as useful that the cosine
; goes off the page
.align $100
sin_table_low:
.byte $00,$06,$0C,$12,$19,$1F,$25,$2B,$31,$38,$3E,$44,$4A,$50,$56,$5C
@ -508,12 +531,18 @@ cos_table_high_tail:
.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
; pre-calc table for R*I
; note this would be easy to calculate at startup
; to save space
rl:
.byte $00,$06,$0C,$12,$19,$1F,$25,$2B
.byte $32,$38,$3E,$45,$4B,$51,$57,$5E
.byte $64,$6A,$71,$77,$7D,$83,$8A,$90
.byte $96,$9D,$A3,$A9,$AF,$B6,$BC,$C2
; which of 7 pixels to draw
; note high bit is set to pick blue/orange palette
; clear to get purple/green instead
log_lookup:
.byte $81,$82,$84,$88,$90,$A0,$C0,$80