Wolf.68k

;
; 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
SGCount	EQU D6
SGDelta	EQU	D4
SGVidWidth EQU D5

	MOVEM.L	D2-D6,-(A7)
	MOVE.L	ParmSGArt(A7),SGArt2
	MOVE.L	ParmScrn(A7),SGScrn
	MOVE.L	ParmTFrac(A7),SGFrac	;Get pointer to the run structure
	MOVE.L	SGFrac,SGInt
	SWAP	SGInt
	MOVE.W	ParmCnt(A7),SGCount
	MOVE.W	ParmDelta(A7),SGDelta
	MOVE.W	VideoWidth,SGVidWidth	;Init the video width 
	MOVE.L	#0,SGArt
	SUB.W	#1,SGCount		;Adjust for count used in DBF
	
Loopy2
	MOVE.B	(SGArt2,SGArt.W),D0	;Get shape byte
	MOVE.B	D0,(SGScrn)
	ADD.W	SGFrac,SGDelta	;Adjust the delta
	ADDX.W	SGInt,SGArt		;Adjust the source byte offset
	ADD.W	SGVidWidth,SGScrn	;Next dest scan line
	DBF		SGCount,Loopy2		;Still more?
	MOVEM.L	(A7)+,D2-D6
	RTS
	END