GSCats/terrain_e1.s

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;
; terrain (in E1 bank)
;
; Fill-mode terrain rendering code snippets
; that live in bank E1 for maximum speed.
;
; Created by Quinn Dunki on 7/29/17
;
.include "equates.s"
.include "macros.s"
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UNRENDERCACHESTACK = $7ff ; Stack downwards from bottom of VRAM. Mirrored from $01 into $E1!
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OP16
.org $800
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; renderTerrainSpans:
;
;
renderTerrainSpans:
SAVE_AXY
SAVE_DBR
FASTGRAPHICS
lda #UNRENDERCACHESTACK ; Prepare unrender cache
tcs
lda #MAXTERRAINHEIGHT-1
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sec
sbc lastCompiledTerrainY
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renderTerrainSpansLoop:
sta PARAML1
; Find row data
lda PARAML1
asl ; Shifts must match SPANROWBYTES
asl
asl
asl
asl
tay
lda terrainSpanData,y
sta SCRATCHL ; Track span color
; Find VRAM row
lda PARAML1
asl
tax
lda vramRowInvertedSpanLookup,x
tax
adc #160
sta PARAML0 ; Watch for end of VRAM row
; Find span that intersects left logical edge
lda #0
clc
renderTerrainRowSpansFindLeftLoop:
adc terrainSpanData+2,y
cmp leftScreenEdge
bpl renderTerrainRowSpansFoundLeft
iny
iny
sta CACHEDATA
lda SCRATCHL
eor #%110000 ; Toggle span color cache
sta SCRATCHL
lda CACHEDATA
bra renderTerrainRowSpansFindLeftLoop
renderTerrainRowSpansFoundLeft:
sec
sbc leftScreenEdge ; A now holds remainder of leftmost span
; and Y points to leftmost span
renderTerrainRowSpansLoop:
sta SCRATCHL2
; Set fill mode byte for this span
lda SCRATCHL
sta VRAMBANK,x
; Cache the index we wrote to so we can erase later
phx
; Advance to end of span
clc
txa
adc SCRATCHL2
cmp PARAML0
bpl renderTerrainRowSpansDone
tax
; Prepare for next span
iny
iny
lda SCRATCHL
eor #%110000 ; Toggle span color cache
sta SCRATCHL
lda terrainSpanData+2,y
bra renderTerrainRowSpansLoop
renderTerrainRowSpansDone:
lda PARAML1
dec
bne renderTerrainSpansLoop
pea 0 ; Null-terminate the unrender cache
SLOWGRAPHICS
RESTORE_DBR
RESTORE_AXY
rtl
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; unrenderTerrainSpans:
;
;
unrenderTerrainSpans:
SAVE_AXY
SAVE_DBR
phb
pea $e1e1 ; Work entirely in bank E1 for all local read/writes
plb
plb
ldy #UNRENDERCACHESTACK-1
unrenderTerrainSpansLoop:
lda 0,y
beq unrenderTerrainSpansDone
tax
lda #0
sta a:0,x
dey
dey
bra unrenderTerrainSpansLoop
unrenderTerrainSpansDone:
plb
RESTORE_DBR
RESTORE_AXY
rtl
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrainSpans:
;
;
compileTerrainSpans:
pha
SAVE_DBR
lda #0
compileTerrainSpansLoop:
sta PARAML1
jsr compileTerrainSpansRow
lda PARAML1
inc
cmp #MAXTERRAINHEIGHT
bne compileTerrainSpansLoop
RESTORE_DBR
pla
rtl
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrainSpansRow:
;
; PARAML1 = Row index (bottom relative)
;
; Trashes SCRATCHL
;
compileTerrainSpansRow:
SAVE_AXY
lda PARAML1
asl ; Shifts must match SPANROWBYTES
asl
asl
asl
asl
clc
adc #terrainSpanData
sta SCRATCHL
ldy #0
ldx #TERRAINWIDTH-2
lda terrainDataFar,x ; Figure out start value for row
cmp PARAML1
bcs compileTerrainSpansRowInitGreen
compileTerrainSpansRowInitBlack:
lda #$0010 ; First span is black
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sta (SCRATCHL) ; Initialize the row
inc SCRATCHL
inc SCRATCHL
ldy #-1
compileTerrainSpansRowBlackStart:
iny
compileTerrainSpansRowBlackLoop:
lda terrainDataFar,x
cmp PARAML1
bcs compileTerrainSpansBlackEnd
dex
dex
iny
cpx #-2
bne compileTerrainSpansRowBlackLoop
compileTerrainSpansBlackEnd:
tya ; Store this span's length
sta (SCRATCHL)
inc SCRATCHL
inc SCRATCHL
dex ; Begin searching for next span
dex
cpx #0
bmi compileTerrainSpansRowDone
ldy #0
bra compileTerrainSpansRowGreenStart
compileTerrainSpansRowDone:
RESTORE_AXY
rts
compileTerrainSpansRowInitGreen:
lda #$0020 ; First span is green
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sta (SCRATCHL) ; Initialize the row
inc SCRATCHL
inc SCRATCHL
ldy #-1
compileTerrainSpansRowGreenStart:
iny
compileTerrainSpansRowGreenLoop:
lda terrainDataFar,x
cmp PARAML1
bcc compileTerrainSpansGreenEnd
dex
dex
iny
cpx #-2
bne compileTerrainSpansRowGreenLoop
compileTerrainSpansGreenEnd:
tya ; Store this span's length
sta (SCRATCHL)
inc SCRATCHL
inc SCRATCHL
dex ; Begin searching for next span
dex
cpx #0
bmi compileTerrainSpansRowDone
ldy #0
bra compileTerrainSpansRowBlackStart
terrainSpanData:
.repeat MAXTERRAINHEIGHT
.word 0 ; Start value (0=BG)
.repeat MAXSPANSPERROW
.word 0 ; Length (in bytes)
.endrepeat
.endrepeat
vramRowInvertedSpanLookup:
.word $9d00,$9c60,$9bc0,$9b20,$9a80,$99e0,$9940,$98a0,$9800,$9760,$96c0,$9620,$9580,$94e0,$9440,$93a0,$9300,$9260,$91c0,$9120
.word $9080,$8fe0,$8f40,$8ea0,$8e00,$8d60,$8cc0,$8c20,$8b80,$8ae0,$8a40,$89a0,$8900,$8860,$87c0,$8720,$8680,$85e0,$8540,$84a0
.word $8400,$8360,$82c0,$8220,$8180,$80e0,$8040,$7fa0,$7f00,$7e60,$7dc0,$7d20,$7c80,$7be0,$7b40,$7aa0,$7a00,$7960,$78c0,$7820
.word $7780,$76e0,$7640,$75a0,$7500,$7460,$73c0,$7320,$7280,$71e0,$7140,$70a0,$7000,$6f60,$6ec0,$6e20,$6d80,$6ce0,$6c40,$6ba0
.word $6b00,$6a60,$69c0,$6920,$6880,$67e0,$6740,$66a0,$6600,$6560,$64c0,$6420,$6380,$62e0,$6240,$61a0,$6100,$6060,$5fc0,$5f20
.word $5e80,$5de0,$5d40,$5ca0,$5c00,$5b60,$5ac0,$5a20,$5980,$58e0,$5840,$57a0,$5700,$5660,$55c0,$5520,$5480,$53e0,$5340,$52a0
.word $5200,$5160,$50c0,$5020,$4f80,$4ee0,$4e40,$4da0,$4d00,$4c60,$4bc0,$4b20,$4a80,$49e0,$4940,$48a0,$4800,$4760,$46c0,$4620
.word $4580,$44e0,$4440,$43a0,$4300,$4260,$41c0,$4120,$4080,$3fe0,$3f40,$3ea0,$3e00,$3d60,$3cc0,$3c20,$3b80,$3ae0,$3a40,$39a0
.word $3900,$3860,$37c0,$3720,$3680,$35e0,$3540,$34a0,$3400,$3360,$32c0,$3220,$3180,$30e0,$3040,$2fa0,$2f00,$2e60,$2dc0,$2d20
.word $2c80,$2be0,$2b40,$2aa0,$2a00,$2960,$28c0,$2820,$2780,$26e0,$2640,$25a0,$2500,$2460,$23c0,$2320,$2280,$21e0,$2140,$20a0
.export renderTerrainSpans
.export unrenderTerrainSpans
.export compileTerrainSpans
; Suppress some linker warnings - Must be the last thing in the file
.SEGMENT "ZPSAVE"
.SEGMENT "EXEHDR"
.SEGMENT "STARTUP"
.SEGMENT "INIT"
.SEGMENT "LOWCODE"