Wolf3D-Mac/Wolf.68k

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