298 lines
4.9 KiB
ArmAsm
298 lines
4.9 KiB
ArmAsm
;
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; terrain (in E1 bank)
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;
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; Fill-mode terrain rendering code snippets
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; that live in bank E1 for maximum speed.
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;
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; Created by Quinn Dunki on 7/29/17
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;
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.include "equates.s"
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.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
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.org $800
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; renderTerrainSpans:
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;
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;
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renderTerrainSpans:
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SAVE_AXY
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SAVE_DBR
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FASTGRAPHICS
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lda #UNRENDERCACHESTACK ; Prepare unrender cache
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tcs
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lda #MAXTERRAINHEIGHT-1
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sec
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sbc lastCompiledTerrainY
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beq renderTerrainRowSpansSkip ; All terrain needs compiled rendering
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renderTerrainSpansLoop:
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sta PARAML1
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; Find row data
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lda PARAML1
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asl ; Shifts must match SPANROWBYTES
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asl
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asl
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asl
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asl
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tay
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lda terrainSpanData,y
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sta SCRATCHL ; Track span color
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; Find VRAM row
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lda PARAML1
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asl
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tax
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lda vramRowInvertedSpanLookup,x
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tax
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adc #160
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sta PARAML0 ; Watch for end of VRAM row
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; Find span that intersects left logical edge
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lda #0
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clc
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renderTerrainRowSpansFindLeftLoop:
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adc terrainSpanData+2,y
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cmp leftScreenEdge
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bpl renderTerrainRowSpansFoundLeft
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iny
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iny
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sta CACHEDATA
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lda SCRATCHL
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eor #%110000 ; Toggle span color cache
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sta SCRATCHL
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lda CACHEDATA
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bra renderTerrainRowSpansFindLeftLoop
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renderTerrainRowSpansFoundLeft:
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sec
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sbc leftScreenEdge ; A now holds remainder of leftmost span
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; and Y points to leftmost span
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renderTerrainRowSpansLoop:
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sta SCRATCHL2
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; Set fill mode byte for this span
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lda SCRATCHL
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sta VRAMBANK,x
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; Cache the index we wrote to so we can erase later
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phx
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; Advance to end of span
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clc
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txa
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adc SCRATCHL2
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cmp PARAML0
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bpl renderTerrainRowSpansDone
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tax
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; Prepare for next span
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iny
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iny
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lda SCRATCHL
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eor #%110000 ; Toggle span color cache
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sta SCRATCHL
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lda terrainSpanData+2,y
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bra renderTerrainRowSpansLoop
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renderTerrainRowSpansDone:
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lda PARAML1
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dec
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bne renderTerrainSpansLoop
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pea 0 ; Null-terminate the unrender cache
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renderTerrainRowSpansSkip:
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SLOWGRAPHICS
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RESTORE_DBR
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RESTORE_AXY
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rtl
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; unrenderTerrainSpans:
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;
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;
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unrenderTerrainSpans:
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SAVE_AXY
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SAVE_DBR
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phb
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pea $e1e1 ; Work entirely in bank E1 for all local read/writes
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plb
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plb
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ldy #UNRENDERCACHESTACK-1
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unrenderTerrainSpansLoop:
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lda 0,y
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beq unrenderTerrainSpansDone
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tax
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lda #0
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sta a:0,x
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dey
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dey
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bra unrenderTerrainSpansLoop
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unrenderTerrainSpansDone:
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plb
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RESTORE_DBR
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RESTORE_AXY
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rtl
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; compileTerrainSpans:
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;
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;
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compileTerrainSpans:
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pha
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SAVE_DBR
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lda #0
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compileTerrainSpansLoop:
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sta PARAML1
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jsr compileTerrainSpansRow
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lda PARAML1
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inc
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cmp #MAXTERRAINHEIGHT
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bne compileTerrainSpansLoop
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RESTORE_DBR
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pla
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rtl
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; compileTerrainSpansRow:
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;
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; PARAML1 = Row index (bottom relative)
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;
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; Trashes SCRATCHL
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;
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compileTerrainSpansRow:
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SAVE_AXY
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lda PARAML1
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asl ; Shifts must match SPANROWBYTES
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asl
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asl
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asl
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asl
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clc
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adc #terrainSpanData
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sta SCRATCHL
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ldy #0
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ldx #TERRAINWIDTH-2
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lda terrainDataFar,x ; Figure out start value for row
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cmp PARAML1
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bcs compileTerrainSpansRowInitGreen
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compileTerrainSpansRowInitBlack:
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lda #$0010 ; First span is black
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sta (SCRATCHL) ; Initialize the row
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inc SCRATCHL
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inc SCRATCHL
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ldy #-1
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compileTerrainSpansRowBlackStart:
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iny
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compileTerrainSpansRowBlackLoop:
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lda terrainDataFar,x
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cmp PARAML1
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bcs compileTerrainSpansBlackEnd
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dex
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dex
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iny
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cpx #-2
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bne compileTerrainSpansRowBlackLoop
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compileTerrainSpansBlackEnd:
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tya ; Store this span's length
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sta (SCRATCHL)
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inc SCRATCHL
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inc SCRATCHL
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dex ; Begin searching for next span
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dex
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cpx #0
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bmi compileTerrainSpansRowDone
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ldy #0
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bra compileTerrainSpansRowGreenStart
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compileTerrainSpansRowDone:
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RESTORE_AXY
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rts
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compileTerrainSpansRowInitGreen:
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lda #$0020 ; First span is green
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sta (SCRATCHL) ; Initialize the row
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inc SCRATCHL
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inc SCRATCHL
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ldy #-1
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compileTerrainSpansRowGreenStart:
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iny
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compileTerrainSpansRowGreenLoop:
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lda terrainDataFar,x
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cmp PARAML1
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bcc compileTerrainSpansGreenEnd
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dex
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dex
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iny
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cpx #-2
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bne compileTerrainSpansRowGreenLoop
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compileTerrainSpansGreenEnd:
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tya ; Store this span's length
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sta (SCRATCHL)
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inc SCRATCHL
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inc SCRATCHL
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dex ; Begin searching for next span
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dex
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cpx #0
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bmi compileTerrainSpansRowDone
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ldy #0
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bra compileTerrainSpansRowBlackStart
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terrainSpanData:
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.repeat MAXTERRAINHEIGHT
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.word 0 ; Start value (0=BG)
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.repeat MAXSPANSPERROW
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.word 0 ; Length (in bytes)
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.endrepeat
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.endrepeat
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vramRowInvertedSpanLookup = $16C0 ; This table is copied to here by the loader
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.export renderTerrainSpans
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.export unrenderTerrainSpans
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.export compileTerrainSpans
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; Suppress some linker warnings - Must be the last thing in the file
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.SEGMENT "ZPSAVE"
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.SEGMENT "EXEHDR"
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.SEGMENT "STARTUP"
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.SEGMENT "INIT"
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.SEGMENT "LOWCODE"
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