136 lines
2.0 KiB
ArmAsm
136 lines
2.0 KiB
ArmAsm
; Tunnel (no multiply), based on the code by Hellmood
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; by deater (Vince Weaver) <vince@deater.net>
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; first try (shift/add multiply) = 160 bytes, 14 seconds/frame
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; second (lookup table mul) = 251 bytes, 9 seconds/frame
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; Zero Page
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COLOR = $30
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XCOORD = $F0
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YCOORD = $F1
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DEPTH = $F2
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VALUE = $F6
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M1 = $F7
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M2 = $F8
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FRAME = $F9
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TEMP = $FA
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; Soft Switches
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KEYPRESS= $C000
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KEYRESET= $C010
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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; ROM routines
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PLOT = $F800 ; plot, horiz=y, vert=A (A trashed, XY Saved)
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SETCOL = $F864
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SETGR = $FB40
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tunnel:
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;===================
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; init screen
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jsr SETGR ; 3
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bit FULLGR ; 3
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; jsr init_multiply_tables ; 3
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tunnel_forever:
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inc FRAME ; 2
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ldx #47 ; 2
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yloop:
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ldy #39 ; 2
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xloop:
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; Xcoord = (x-10)*4
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sec ; 1
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tya ; 1
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sbc #10 ; 2
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asl ; 1
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asl ; 1
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sta XCOORD ; 2
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; Ycoord = (y-10)*4
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sec ; 1
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txa ; 1
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sbc #10 ; 2
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asl ; 1
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asl ; 1
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; center
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sbc #24
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sta YCOORD ; 2
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; set depth to -9 (move backwards)
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lda #$f7 ; 2
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sta DEPTH ; 2
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fx5_loop:
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; get ycoord
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lda YCOORD ; 2
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; 8x8 signed multiply of M1*DEPTH
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;sta M1 ; 2
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; jsr imul ; 3
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; lda M2 ; 2
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sta VALUE ; high result in A ; 2
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; get xcoord
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lda XCOORD ; 2
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; add distance to projection (bend right)
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clc ; 1
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adc DEPTH ; 2
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;sta M1 ; 2
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; 8x8 signed multiply of M1*DEPTH
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; jsr imul ; 3
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; do the calculation
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dec DEPTH ; 2
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beq putpixel ; 2 ; is this needed?
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; load the yprojection
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lda VALUE ; 2
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; xor with the xprojection
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eor M2 ; 2
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; center walls around 0
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clc ; 1
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adc #$4 ; 2
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; test with -8, see if wall hit
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sta VALUE ; 2
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and #$f8 ; 2
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beq fx5_loop ; 2
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putpixel:
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; adjust color by frame and set
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sec ; 1
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lda DEPTH ; 2
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sbc FRAME ; 2
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eor VALUE ; 2
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and #$7 ; 2
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;adc #$20
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jsr SETCOL ; 3
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txa ; A==Y1 ; 1
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jsr PLOT ; (X2,Y1) ; 3
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dey ; 1
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bpl xloop ; 2
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dex ; 1
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bpl yloop ; 2
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bmi tunnel_forever ; 2
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