GSCats/terrain.s
blondie7575 4a9958e5ac Added power indicator to crosshair
Fixed years-old bug in terrain unclipper which caused it to spray garbage in bank 3. My god, what a bug.
2023-06-25 18:43:07 -07:00

554 lines
8.9 KiB
ArmAsm

;
; terrain
;
; Created by Quinn Dunki on 7/29/17
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; renderTerrain
;
; No stack operations permitted here!
;
; Trashes all registers
;
renderTerrain:
FASTGRAPHICS
lda #0
sta SCRATCHL2 ; Row counter
lda #$5f1f ; 4 Point stack to end of affected VRAM
tcs ; 2
sec
lda #compiledTerrainEnd-VISIBLETERRAINWINDOW-4
sbc mapScrollPos
sta PARAML0
renderTerrainLoop:
; Note that DP register is normally $0000, so that is used as the BG/BG case
lda #$0011 ; BG/FG
ldx #$1111 ; FG/FG
ldy #$1100 ; FG/BG
jmp (PARAML0)
renderRowComplete:
lda PARAML0
sec
sbc #COMPILEDTERRAINROW
sta PARAML0
tsc
clc
adc #320
tcs
lda SCRATCHL2
inc
cmp lastCompiledTerrainY
beq renderRowCont
bcs renderTerrainDone
renderRowCont:
sta SCRATCHL2
bra renderTerrainLoop
renderTerrainDone:
SLOWGRAPHICS
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; craterTerrain
;
; PARAML0 = X pos of center in pixels from logical left terrain edge
; PARAML1 = Y pos of center in pixels from bottom terrain edge
; Y = Radius of circle, in pixels (minimum is 3)
;
; Trashes SCRATCHL
craterTerrain:
SAVE_AX
stz craterTerrainAccumulator
lda #TERRAINWIDTH ; Convert X pos to terrain-right byte count
sec
sbc PARAML0
sty SCRATCHL ; Center width in bytes
sbc SCRATCHL
sbc SCRATCHL
and #$fffe ; Force even
clc
adc #terrainData
sta PARAML0
tya
asl
tay
lda circleTable,y ; Look up circle data
sta SCRATCHL
tya ; Iterate over diameter words
asl
tay
craterTerrainLoop:
dey
dey
bmi craterTerrainDone
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
bmi craterTerrainZero
sta SCRATCHL2
sec
lda (PARAML0),y
sbc SCRATCHL2
bmi craterTerrainLoop
; Circle value is lower, so use that
clc
adc craterTerrainAccumulator ; Track total crater material
sta craterTerrainAccumulator
lda SCRATCHL2 ; Replace terrain height with cratered value
sta (PARAML0),y
bra craterTerrainLoop
craterTerrainZero: ; Circle went negative so clip to 0
lda #0
sta (PARAML0),y
bra craterTerrainLoop
craterTerrainDone:
lda #1
sta terrainDirty
RESTORE_AX
rts
craterTerrainAccumulator:
.word 0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; clipTerrain
;
; 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
; Shadow stack into $E04000 to save clipped data fast
tsc
sta STACKPTR
lda #CLIPPEDTERRAINSTACK
tcs
sec
lda #COMPILEDTERRAINROW*MAXTERRAINHEIGHT-4
sbc mapScrollPos
tay
ldx #0
clipTerrainLoop:
lda compiledTerrain,y
pha
lda #$4cea ; NOP followed by JMP
sta compiledTerrain,y
iny
iny
lda compiledTerrain,y
pha
lda #renderRowComplete
sta compiledTerrain,y
tya
sec
sbc #COMPILEDTERRAINROW+2
tay
inx
cpx lastCompiledTerrainY
bcc clipTerrainLoop
beq clipTerrainLoop
; Put stack back where it belongs
tsc
sta clippedTerrainStackPtr
lda STACKPTR
tcs
RESTORE_AXY
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; unclipTerrain
;
; 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.
;
; On first move-left unclip every second row is unclipped incorrectly
unclipTerrain:
SAVE_AXY
phd
lda #(CLIPPEDTERRAINSTACK & $f000)
pha
pld ; Point direct page at our clip data
sec
lda #COMPILEDTERRAINROW*MAXTERRAINHEIGHT-4
sbc mapScrollPos
tay
sec ; Find stopping point for stack-relative addressing
lda clippedTerrainStackPtr
and #$0fff
sbc #3 ; -3 for starting offset
sta STACKPTR
lda #$0fff-3 ; Start at the bottom of the stack
tax
unclipTerrainLoop:
lda 2,x
sta compiledTerrain,y
iny
iny
lda 0,x
sta compiledTerrain,y
tya
sec
sbc #COMPILEDTERRAINROW+2
tay
dex ; Walk up the stack to reverse the data
dex
dex
dex
cpx STACKPTR ; When x hits the top of the stack, we're done
bne unclipTerrainLoop
pld
RESTORE_AXY
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrain
;
;
;
compileTerrain:
SAVE_AY
ldy #0
lda #compiledTerrain
sta PARAML0
compileTerrainLoop:
sty PARAML1
jsr compileTerrainRow
iny
cpy #MAXTERRAINHEIGHT
beq compileTerrainDone
clc
lda #COMPILEDTERRAINROW
adc PARAML0
sta PARAML0
bra compileTerrainLoop
compileTerrainDone:
RESTORE_AY
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrainChunk
;
; Y = First row to compile (bottom-relative)
; X = Last row to compile (bottom-relative)
; A = |X-Y|
;
; Trashes A,Y, SCRATCHL, PARAML0, PARAML1
;
compileTerrainChunk:
;HARDBRK
stx SCRATCHL
sty PARAML0
; Compute the start of memory affected
lda #COMPILEDTERRAINROW
sta PARAML1
jsr mult16
clc
adc #compiledTerrain
sta PARAML0
compileTerrainChunkLoop:
sty PARAML1
;HARDBRK
jsr compileTerrainRow
iny
cpy SCRATCHL
beq compileTerrainChunkDone
clc
lda #COMPILEDTERRAINROW
adc PARAML0
sta PARAML0
bra compileTerrainChunkLoop
compileTerrainChunkDone:
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; compileTerrainRow
;
; PARAML0 = Start of compiled row data
; PARAML1 = Row index
;
; Note: DA = PHX = FG/FG
; 48 = PHA = FG/BG
; 5A = PHY = BG/FG
; 0B = PHD = BG/BG
compileTerrainRow:
SAVE_AXY
ldy #0
ldx #0
compileTerrainColumnLoop:
stz compileTerrainOpcode
; Check column 0
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn0BG
beq compileTerrainColumn0BG
; Column 0 is FG, so check column 1
inx
inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn1BG
beq compileTerrainColumn1BG
; Columns 0 and 1 are FG/FG, so PHX
lda #$00da
compileTerrainColumn2:
sta compileTerrainOpcode ; Cache results so far
; Check column 2
inx
inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn2BG
beq compileTerrainColumn2BG
; Column 2 is FG, so check column 3
inx
inx
lda terrainData,x
cmp PARAML1
bcc compileTerrainColumn3BG
beq compileTerrainColumn3BG
; Columns 2 and 3 are FG/FG, so PHX
lda compileTerrainOpcode
ora #$da00
compileTerrainColumnStore:
sta (PARAML0),y
inx
inx
iny
iny
cpy #VISIBLETERRAINWIDTH
bne compileTerrainColumnLoop
RESTORE_AXY
rts
compileTerrainColumn0BG:
; Column 0 is BG, so check column 1
inx
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
compileTerrainColumn1BG:
; Columns 0 and 1 are FG/BG, so PHY
lda #$005a
bra compileTerrainColumn2
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
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:
.word 0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; prepareRowRendering:
;
; Set SCBs to match rendering mode of each terrain line
;
; Trashes SCRATCHL, SCRATCHL2
;
prepareRowRendering:
SAVE_AXY
ldx #199
stz SCRATCHL2
stz lastCompiledTerrainY
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
inc lastCompiledTerrainY
prepareRowRenderingLoopNext:
inc SCRATCHL2
dex
cpx #200-MAXTERRAINHEIGHT
bne prepareRowRenderingLoop
prepareRowRenderingDone:
;HARDBRK
RESTORE_AXY
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; generateTerrain
;
; Trashes everything
;
generateTerrain:
ldy #0
ldx #0
lda #terrainData
sta SCRATCHL
generateTerrainLoop:
lda sineTable,x
lsr
lsr
clc
adc #30
sta (SCRATCHL),y
iny
iny
inx
inx
inx
inx
txa
and #$03ff
tax
cpy #TERRAINWIDTH
bne generateTerrainLoop
; lda #1 ; Debug values
; sta terrainData
; lda #2
; sta compiledTerrain-4
rts
compiledTerrain:
.repeat COMPILEDTERRAINROW * MAXTERRAINHEIGHT
.byte $42
.endrepeat
compiledTerrainEnd:
clippedTerrainStackPtr:
.word 0