GSCats/terrain.s

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;
; terrain
;
; Created by Quinn Dunki on 7/29/17
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; renderTerrain
;
; No stack operations permitted here!
;
; Trashes all registers
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;
renderTerrain:
FASTGRAPHICS
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lda #0
sta SCRATCHL2 ; Row counter
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lda #$5f1f ; 4 Point stack to end of affected VRAM
tcs ; 2
sec
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lda #compiledTerrainEnd-VISIBLETERRAINWINDOW-4
sbc mapScrollPos
sta PARAML0
renderTerrainLoop:
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; Note that DP register is normally $0000, so that is used as the BG/BG case
lda #$0011 ; BG/FG
ldx #$1111 ; FG/FG
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ldy #$1100 ; FG/BG
jmp (PARAML0)
renderRowComplete:
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lda PARAML0
sec
sbc #COMPILEDTERRAINROW
sta PARAML0
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tsc
clc
adc #320
tcs
lda SCRATCHL2
inc
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cmp lastCompiledTerrainY
beq renderRowCont
bcs renderTerrainDone
renderRowCont:
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sta SCRATCHL2
bra renderTerrainLoop
renderTerrainDone:
SLOWGRAPHICS
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; craterTerrain
;
; PARAML0 = X pos of center in pixels from logical left terrain edge
; PARAML1 = Y pos of center in pixels from bottom terrain edge
; Y = Radius of circle, in pixels
;
; Trashes SCRATCHL
craterTerrain:
SAVE_AX
lda #TERRAINWIDTH ; Convert X pos to terrain-right byte count
sec
sbc PARAML0
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sty SCRATCHL ; Center width in bytes
sbc SCRATCHL
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and #$fffe ; Force even
clc
adc #terrainData
sta PARAML0
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lda circleTable,y ; Look up circle data
sta SCRATCHL
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tya ; Iterate over diameter
asl
tay
craterTerrainLoop:
dey
dey
bmi craterTerrainDone
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tya
clc
adc PARAML0 ; Clip to terrain edges
cmp #terrainData
bmi craterTerrainDone
cmp #terrainDataEnd
bpl craterTerrainLoop
lda (SCRATCHL),y ; Fetch circle Y value
clc
adc PARAML1 ; Convert to terrain-space
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bmi craterTerrainZero
sta SCRATCHL2
lda (PARAML0),y
cmp SCRATCHL2
bmi craterTerrainLoop
lda SCRATCHL2 ; Circle value is lower, so use that
sta (PARAML0),y
bra craterTerrainLoop
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craterTerrainZero: ; Circle went negative so clip to 0
lda #0
sta (PARAML0),y
bra craterTerrainLoop
craterTerrainDone:
lda #1
sta terrainDirty
RESTORE_AX
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; clipTerrain
;
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; Saves the compiled terrain data that we overwrite into
; a buffer at $E04000. We do this by shadowing the stack
; to that area and pushing.
;
clipTerrain:
SAVE_AXY
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; Shadow stack into $E04000 to save clipped data fast
tsc
sta STACKPTR
lda #CLIPPEDTERRAINSTACK
tcs
sec
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lda #COMPILEDTERRAINROW*MAXTERRAINHEIGHT-4
sbc mapScrollPos
tay
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ldx #0
clipTerrainLoop:
lda compiledTerrain,y
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pha
lda #$4cea ; NOP followed by JMP
sta compiledTerrain,y
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iny
iny
lda compiledTerrain,y
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pha
lda #renderRowComplete
sta compiledTerrain,y
tya
sec
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sbc #COMPILEDTERRAINROW+2
tay
inx
cpx lastCompiledTerrainY
bcc clipTerrainLoop
beq clipTerrainLoop
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; Put stack back where it belongs
tsc
sta clippedTerrainStackPtr
lda STACKPTR
tcs
RESTORE_AXY
rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; unclipTerrain
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;
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; Restores the compiled terrain data that we wrote
; to a buffer at $E04000. We do this by mapping the stack
; to $4000, then using stack-relative addressing to pull the data.
; We can't pop the data because it's all stored in reverse.
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;
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; On first move-left unclip every second row is unclipped incorrectly
unclipTerrain:
SAVE_AXY
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phd
lda #(CLIPPEDTERRAINSTACK & $ff00)
pha
pld ; Point direct page at our clip data
sec
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lda #COMPILEDTERRAINROW*MAXTERRAINHEIGHT-4
sbc mapScrollPos
tay
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lda clippedTerrainStackPtr
and #$00ff
tax
inx
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unclipTerrainLoop:
lda 2,x
sta compiledTerrain,y
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iny
iny
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lda 0,x
sta compiledTerrain,y
tya
sec
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sbc #COMPILEDTERRAINROW+2
tay
inx
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inx
inx
inx
cpx #$100 ; When x hits the top of the stack, we're done
bne unclipTerrainLoop
pld
RESTORE_AXY
rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrain
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;
;
;
compileTerrain:
SAVE_AY
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ldy #0
lda #compiledTerrain
sta PARAML0
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compileTerrainLoop:
sty PARAML1
jsr compileTerrainRow
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iny
cpy #MAXTERRAINHEIGHT
beq compileTerrainDone
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clc
lda #COMPILEDTERRAINROW
adc PARAML0
sta PARAML0
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bra compileTerrainLoop
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compileTerrainDone:
jsl compileTerrainSpans
RESTORE_AY
rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrainRow
;
; PARAML0 = Start of compiled row data
; PARAML1 = Row index
;
; Note: DA = PHX = FG/FG
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; 48 = PHA = FG/BG
; 5A = PHY = BG/FG
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; 0B = PHD = BG/BG
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compileTerrainRow:
SAVE_AXY
ldy #0
ldx #0
compileTerrainColumnLoop:
stz compileTerrainOpcode
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; Check column 0
lda terrainData,x
cmp PARAML1
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bcc compileTerrainColumn0BG
beq compileTerrainColumn0BG
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; Column 0 is FG, so check column 1
inx
inx
lda terrainData,x
cmp PARAML1
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bcc compileTerrainColumn1BG
beq compileTerrainColumn1BG
; Columns 0 and 1 are FG/FG, so PHX
lda #$00da
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compileTerrainColumn2:
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sta compileTerrainOpcode ; Cache results so far
; Check column 2
inx
inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn2BG
beq compileTerrainColumn2BG
; Column 2 is FG, so check column 3
inx
inx
lda terrainData,x
cmp PARAML1
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bcc compileTerrainColumn3BG
beq compileTerrainColumn3BG
; Columns 2 and 3 are FG/FG, so PHX
lda compileTerrainOpcode
ora #$da00
compileTerrainColumnStore:
sta (PARAML0),y
inx
inx
iny
iny
cpy #VISIBLETERRAINWIDTH
bne compileTerrainColumnLoop
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RESTORE_AXY
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rts
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compileTerrainColumn0BG:
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; Column 0 is BG, so check column 1
inx
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inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn01BG
beq compileTerrainColumn01BG
; Columns 0 and 1 are BG/FG, so PHA
lda #$0048
bra compileTerrainColumn2
compileTerrainColumn01BG:
; Columns 0 and 1 are BG/BG, so PHD
lda #$000b
bra compileTerrainColumn2
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compileTerrainColumn1BG:
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; Columns 0 and 1 are FG/BG, so PHY
lda #$005a
bra compileTerrainColumn2
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compileTerrainColumn2BG:
; Column 2 is BG, so check column 3
inx
inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn23BG
beq compileTerrainColumn23BG
; Columns 2 and 3 are BG/FG, so PHA
lda compileTerrainOpcode
ora #$4800
bra compileTerrainColumnStore
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compileTerrainColumn23BG:
; Columns 2 and 3 are BG, so PHD
lda compileTerrainOpcode
ora #$0b00
bra compileTerrainColumnStore
compileTerrainColumn3BG:
; Columns 2 and 3 are FG/BG, so PHY
lda compileTerrainOpcode
ora #$5a00
bra compileTerrainColumnStore
compileTerrainOpcode:
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.word 0
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; prepareRowRendering:
;
; Set SCBs to match rendering mode of each terrain line
;
; Trashes SCRATCHL, SCRATCHL2
;
prepareRowRendering:
SAVE_AXY
ldx #199
stz SCRATCHL2
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stz lastCompiledTerrainY
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prepareRowRenderingLoop:
lda #0
PLAYERPTR_Y
sec
lda playerData+GO_POSY,y
sbc #GAMEOBJECTHEIGHT
cmp SCRATCHL2
bcc prepareRowRenderingCompileMode
beq prepareRowRenderingCompileMode
jsr enableFillMode
bra prepareRowRenderingLoopNext
prepareRowRenderingCompileMode:
jsr disableFillMode
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inc lastCompiledTerrainY
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prepareRowRenderingLoopNext:
inc SCRATCHL2
dex
cpx #200-MAXTERRAINHEIGHT
bne prepareRowRenderingLoop
RESTORE_AXY
rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; generateTerrain
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;
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; Trashes everything
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;
generateTerrain:
ldy #0
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ldx #0
lda #terrainData
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sta SCRATCHL
generateTerrainLoop:
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lda sineTable,x
lsr
lsr
clc
adc #30
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sta (SCRATCHL),y
iny
iny
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inx
inx
inx
inx
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txa
and #$03ff
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tax
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cpy #TERRAINWIDTH
bne generateTerrainLoop
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; lda #1 ; Debug values
; sta terrainData
; lda #2
; sta compiledTerrain-4
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rts
compiledTerrain:
.repeat COMPILEDTERRAINROW * MAXTERRAINHEIGHT
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.byte $00
.endrepeat
compiledTerrainEnd:
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clippedTerrainStackPtr:
.word 0
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