1 line
4.7 KiB
Plaintext
1 line
4.7 KiB
Plaintext
;
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; Assembly language functions for wolf 3-D
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; By Bill Heineman
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; 9-12-94 (Rev to use tight loop for scale code)
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;
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; Call the compiled scaler
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; void ScaleGlue(void *TextPtr,t_compscale *CodePtr);
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;
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CASE ON
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WALLHEIGHT EQU 128+1
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EXPORT IO_ScaleWallColumn
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EXPORT SpriteGlue
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IMPORT VideoPointer:DATA
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IMPORT VideoWidth:DATA
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IMPORT ScaleDiv:DATA
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IMPORT ArtData:DATA
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IMPORT MacViewHeight:DATA
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IO_ScaleWallColumn PROC
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Adder1 EQU 20
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ParmX EQU 4+Adder1
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ParmScale EQU 6+Adder1
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ParmTile EQU 8+Adder1
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ParmColumn EQU 10+Adder1
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;
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; D0 = Temp, A0 = Temp
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;
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RegScrn EQU A0 ;Pointer to the screen
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RegArt2 EQU A1 ;True pointer to art
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RegArt EQU D1 ;Offset into the shape
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RegDelta EQU D2 ;Delta counter
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RegFrac EQU D3 ;Fixed point fraction
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RegInt EQU D4 ;Fixed point integer
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RegVidWidth EQU D5 ;Width of the screen in bytes
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RegScale EQU D6 ;Scale factor
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MOVEM.L D2-D6,-(A7) ;Save my registers
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MOVE.L #0,RegScale ;Force scale to a long value
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MOVE.W ParmScale(A7),RegScale ;Preload the scale factor
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CMP.W #0,RegScale ;Scale of zero?
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BEQ.S ByeBye ;Exit now! (Can't draw zero height)
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MOVE.W ParmX(A7),D0 ;Get the X coord
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MOVE.L VideoPointer,RegScrn ;Init the screen pointer
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ADD.W D0,RegScrn ;Add the X coord
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MOVE.W VideoWidth,RegVidWidth ;Init the video width
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LEA ScaleDiv,RegArt2 ;Get pointer to the scaler recipocal table
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MOVE.W RegScale,D0 ;Place scale value in temp
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LSL.W #2,D0 ;Mul by 4 for longword index
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MOVE.L (RegArt2,D0.W),RegFrac ;Get the precalced fraction
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ADD.W RegScale,RegScale ;Convert scale to pixel value
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MOVE.W ParmColumn(A7),RegArt ;Get the column index to the art
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LSL.W #7,RegArt ;I have the pixel index
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MOVE.W ParmTile(A7),D0
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LSL.W #2,D0 ;Shift down 7 up 2
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LEA ArtData,RegArt2 ;Get pointer to my shape ptr array
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MOVE.L (RegArt2,D0.W),RegArt2 ;Get the base pointer to the art in A2
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MOVE.W MacViewHeight,D0 ;Get the height
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CMP.W D0,RegScale ;Clipping needed?
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BCC.S ClipTop ;Do the clipped version
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SUB.W RegScale,D0 ;How many line are clear?
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LSR.W #1,D0 ;Number of lines to jump DOWN (Center it)
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MULU.W RegVidWidth,D0 ;Mul by bytes per line
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ADD.L D0,RegScrn ;Add to the screen pointer
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MOVE.L RegFrac,RegInt ;Copy the full fixed point number
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SWAP RegInt ;Isolate the integer
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MOVE.W #0,RegDelta ;Zap the delta
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SUB.W #1,RegScale ;-1 from the count for DBF
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;
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; This is the tight loop that draws the scaled line
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; RegArt2/RegArt = Source ptr
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; RegScrn = Video pointer
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; RegFrac = Scale fraction
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; RegInt = Scale integer
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; RegDelta = Scale delta
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; RegScale = Pixel count (Max MacViewHeight)
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;
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Loopy
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MOVE.B (RegArt2,RegArt.W),D0 ;Move shape byte
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MOVE.B D0,(RegScrn)
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ADD.W RegFrac,RegDelta ;Adjust the delta
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ADDX.W RegInt,RegArt ;Adjust the source byte offset
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ADD.W RegVidWidth,RegScrn ;Next dest scan line
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DBF RegScale,Loopy ;Still more?
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ByeBye ;Exit
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MOVEM.L (A7)+,D2-D6
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RTS
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ClipTop
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SUB.W D0,RegScale ;Number of lines clipped
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LSR.W #1,RegScale ;True number of lines skipped from top
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MOVE.W RegFrac,RegDelta ;Init the delta for the mul
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MULU.W RegScale,RegDelta ;Make the new delta for skipped lines
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MOVE.L RegDelta,D0 ;Copy the delta
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SWAP D0 ;Isolate the integer
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ADD.W D0,RegArt ;Skip the hidden lines
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MOVE.L RegFrac,D0
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SWAP D0
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MULU.W RegScale,D0
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ADD.W D0,RegArt
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MOVE.L RegFrac,RegInt ;Copy the full fixed point number
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SWAP RegInt ;Isolate the integer
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MOVE.W MacViewHeight,RegScale ;Use maximum height
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SUB.W #1,RegScale ;Adjust for DBF
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JMP Loopy
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;
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; Call the compiled scaler to draw a run of the line
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;
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;void SpriteGlue(Byte *a,LongWord b,Byte *c,Word d,Word e);
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SpriteGlue PROC
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Off EQU 20
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ParmSGArt EQU 4+Off ;Pointer to the 6 byte run structure
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ParmTFrac EQU 8+Off ;Pointer to the scaler
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ParmScrn EQU 12+Off ;Pointer to the run base address
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ParmCnt EQU 16+Off ;Line count
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ParmDelta EQU 18+Off ;Initial delta
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SGArt2 EQU A0 ;Pointer to the 6 byte run structure
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SGScrn EQU A1 ;Pointer to the run base address
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SGArt EQU D1
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SGFrac EQU D2 ;Pointer to the scaler
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SGInt EQU D3 ;Pointer to the video
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SGCount EQU D6
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SGDelta EQU D4
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SGVidWidth EQU D5
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MOVEM.L D2-D6,-(A7)
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MOVE.L ParmSGArt(A7),SGArt2
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MOVE.L ParmScrn(A7),SGScrn
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MOVE.L ParmTFrac(A7),SGFrac ;Get pointer to the run structure
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MOVE.L SGFrac,SGInt
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SWAP SGInt
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MOVE.W ParmCnt(A7),SGCount
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MOVE.W ParmDelta(A7),SGDelta
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MOVE.W VideoWidth,SGVidWidth ;Init the video width
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MOVE.L #0,SGArt
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SUB.W #1,SGCount ;Adjust for count used in DBF
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Loopy2
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MOVE.B (SGArt2,SGArt.W),D0 ;Get shape byte
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MOVE.B D0,(SGScrn)
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ADD.W SGFrac,SGDelta ;Adjust the delta
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ADDX.W SGInt,SGArt ;Adjust the source byte offset
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ADD.W SGVidWidth,SGScrn ;Next dest scan line
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DBF SGCount,Loopy2 ;Still more?
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MOVEM.L (A7)+,D2-D6
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RTS
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END
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