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raycast: some optimization
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Vince Weaver
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8c820ab203
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@ -3,11 +3,13 @@
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; coded by huseyin kilic (wisdom)
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; copyright (c) 2009-2013 crescent
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.include "hardware.inc"
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; zero page
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V2 = $2D
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COLOR = $30
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RAYPOSX = $61
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RAYPOSXH = $62
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RAYPOSY = $63
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@ -66,6 +68,9 @@ main:
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;---------------------------------------
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; sin/cos table generator
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;---------------------------------------
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; first generate sine for 0..63 (0..90 degrees)
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lda #$00
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tay
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gensin_loop:
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@ -82,13 +87,18 @@ gensin_loop:
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; x = $00
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; y = $40
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; next generate
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gensin_loop2:
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lda sin_t,X
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sta sin_t+$0100,X ; needed for cos extension
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sta sin_t-1+$40,Y
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eor #$ff
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sta sin_t+$80,X
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sta sin_t-1+$c0,Y
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sta sin_t+$0100,X ; copy at $100 so cosine easier
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sta sin_t-1+$40,Y ; store 90-180 degrees
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eor #$ff ; invert
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sta sin_t+$80,X ; store for 180-270 degrees
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sta sin_t-1+$c0,Y ; store for 270-360 degrees
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inx
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dey
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bpl gensin_loop2
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@ -100,7 +110,7 @@ gensin_loop2:
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loop_main:
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; cast 40 rays for each screen column
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; starting with rightmost one
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; yr is used as global column index
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; Y is used as global column index
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; throughout the rest of the program
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ldy #39
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@ -108,7 +118,7 @@ loop_ray:
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; determine current ray's direction
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; by taking player's current direction
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; and fov into account
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; fov is 40 brads out of 256 brads
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; fov is 40 b-rads out of 256 b-rads
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tya
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clc
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@ -151,27 +161,22 @@ loop_dist:
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jsr addsteptopos
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; on return from last call, ar is cell (block) value
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; ar = 0 means empty cell, so continue tracing
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; A == 0 means empty cell, so continue tracing
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beq loop_dist
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skip_dist:
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; now ar contains the value in reached map position
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; now A contains the value in reached map position
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; (or last cell value fetched if max distance is reached)
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; use ar or xr to colorize the block
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; use A or X to colorize the block
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; and #$07
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; ora #$03
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stx COLORS+1
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sta COLORS+1
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; find out visible block height
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; according to distance
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ldx #$ff
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txa
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; fill the single char that appears on screen
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; (as in char $a0 in default charset)
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; dirty but needed because of size restriction
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; sta $2900,y
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; txa
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; calculate visible block height through simple division
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lda #<blocksize
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@ -181,120 +186,82 @@ loop_div:
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sbc DISTANCE
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bcs loop_div
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; xr = half of visible block height
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; X = half of visible block height
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txa
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;---------------------------------------
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; vertical line
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;---------------------------------------
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; yr = x position (screen column)
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; ar = half height (zero height is ok)
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cmp #13 ; height > 12?
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; Y = x position (screen column)
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; A = half height (zero height is ok)
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cmp #24 ; height > 24?
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bcc vline_validheight
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lda #12 ; make sure max height = 12
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lda #23 ; make sure max height = 24
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vline_validheight:
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asl ; calculate full height
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sta HEIGHTS+1 ; store for looping below
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eor #$ff ; subtract full height from screen height
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; sec ; (24 rows)
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adc #24+1 ; +1 because of sec
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; sec ; (48 rows)
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adc #48+1 ; +1 because of sec
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lsr ; sky/floor heights are equal to each other
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sta HEIGHTS
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sta HEIGHTS+2
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.if 0
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; jsr setheights ; dirty again, but works
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;F2C1 85 F8 STA $F8
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;F2C3 85 FA STA $FA
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;F2C5 4C 7D F4 JMP $F47D
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;F47D 38 SEC
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;
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;F47E A9 F0 LDA #$F0
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;F480 4C 2D FE JMP $FE2D
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;FE2D 8E 83 02 STX $0283
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;
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;FE30 8C 84 02 STY $0284
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;FE33 60 RTS
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.endif
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; loop through 3 sections of one screen column
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; i.e. sky - wall - floor
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ldx #$02
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; ldx #$02
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vline_loop:
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; load color
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; lda COLORS,X
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; jsr SETCOL
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sty $FE
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; vline sky, 0 to heights[0]
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; VLINE A,$2D at Y
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lda #$77 ; sky blue
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sta COLOR
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; vline sky
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lda #$77
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jsr SETCOL
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lda HEIGHTS
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sta $2D
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lda HEIGHTS+0
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sta V2
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lda #0
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ldy $FE
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; ldy $FE
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jsr VLINE
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jsr VLINE ; VLINE A,$2D at Y (Y preserved, A=V2)
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; vline wall
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; vline wall, heights[0] to heights[0]+heights[1]
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lda #$FF
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jsr SETCOL
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ldx COLORS+1
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stx COLOR
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lda HEIGHTS
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; A already HEIGHTS+0
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; lda HEIGHTS+0
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clc
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adc HEIGHTS+1
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sta $2D
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lda HEIGHTS
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sta V2
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ldy $FE
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lda HEIGHTS+0
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; ldy $FE
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jsr VLINE ; VLINE A,$2D at Y
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; vline floor
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; vline floor, heights[0]+heights[1]-47
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lda #$66
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jsr SETCOL
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ldx #$88
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stx COLOR
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lda #47
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sta $2D
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ldx #47
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stx V2
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lda HEIGHTS
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clc
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adc HEIGHTS+1
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ldy $FE
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; A already heights[0]+heights[1]
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; lda HEIGHTS
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; clc
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; adc HEIGHTS+1
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; ldy $FE
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jsr VLINE ; VLINE A,$2D at Y
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ldy $FE
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; ldy $FE
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.if 0
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dec HEIGHTS,X
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bmi vline_sectioncomplete
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txs ; dirty way of saving xr temporarily
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ldx CURRENTROW ; this was reset before the distance loop
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; there are two ways used in this program to set up
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; current row address, either through kernal call ($e549)
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; or by directly modifiying zp pointer
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;jsr setrowptr ; call $e549 in main if you comment out this line
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lda linel_t,x
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sta ROWPTR
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lda LINEH_T,x
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sta ROWPTRH
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tsx
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lda COLORS,x ; each section can be assigned to a different color
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sta (ROWPTR),y
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; advance to next screen row
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inc CURRENTROW
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bne vline_loop ; absolute jump, as CURRENTROW never reaches zero
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vline_sectioncomplete:
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; advance to next column section
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dex
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bpl vline_loop
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.endif
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;---------------------------------------
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; advance to next ray/column
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