ref: 6638e8580dee0e8691a54da80058be66ab78bcd4
dir: /dr.asm/
IDEAL MODEL MEDIUM,C P286 SCREENSEG = 0a000h FINEANGLES = 3600 DEG90 = 900 DEG180 = 1800 DEG270 = 2700 DEG360 = 3600 OP_JLE = 07eh OP_JGE = 07dh EXTRN finetangent:DWORD ; far array, starts at offset 0 EXTRN HitHorizWall:FAR EXTRN HitVertWall:FAR EXTRN HitHorizDoor:FAR EXTRN HitVertDoor:FAR EXTRN HitHorizPWall:FAR EXTRN HitVertPWall:FAR DATASEG EXTRN viewwidth:WORD EXTRN tilemap:BYTE EXTRN spotvis:BYTE EXTRN pixelangle:WORD EXTRN midangle:WORD EXTRN angle:WORD EXTRN focaltx:WORD EXTRN focalty:WORD EXTRN viewtx:WORD EXTRN viewty:WORD EXTRN viewx:DWORD EXTRN viewy:DWORD EXTRN xpartialup:WORD EXTRN ypartialup:WORD EXTRN xpartialdown:WORD EXTRN ypartialdown:WORD EXTRN tilehit:WORD EXTRN pixx:WORD EXTRN wallheight:WORD ; array of VIEWWIDTH entries EXTRN xtile:WORD EXTRN ytile:WORD EXTRN xtilestep:WORD EXTRN ytilestep:WORD EXTRN xintercept:DWORD EXTRN yintercept:DWORD EXTRN xstep:DWORD EXTRN ystep:DWORD EXTRN doorposition:WORD ; table of door position values EXTRN pwallpos:WORD ; amound a pushable wall has been moved CODESEG ;------------------- ; ; xpartialbyystep ; ; multiplies long [ystep] (possibly negative), by word [xpartial] (in BX) ; ; returns dx:ax ; trashes bx,cx,di ; ;------------------- PROC xpartialbyystep NEAR ; ; setup ; mov ax,[WORD ystep] mov cx,[WORD ystep+2] or cx,cx ; is ystep negatice? jns @@multpos ; ; multiply negative cx:ax by bx ; neg cx neg ax sbb cx,0 mul bx ; fraction*fraction mov di,dx ; di is low word of result mov ax,cx ; mul bx ; units*fraction add ax,di adc dx,0 neg dx neg ax sbb dx,0 ret ; ; multiply positive cx:ax by bx ; EVEN @@multpos: mul bx ; fraction*fraction mov di,dx ; di is low word of result mov ax,cx ; mul bx ; units*fraction add ax,di adc dx,0 ret ENDP ;------------------- ; ; ypartialbyxstep ; ; multiplies long [xstep] (possibly negative), by word [ypartial] (in BP) ; ; returns dx:ax ; trashes cx,di,bp ; ;------------------- PROC ypartialbyxstep NEAR ; ; setup ; mov ax,[WORD xstep] mov cx,[WORD xstep+2] or cx,cx ; is ystep negatice? jns @@multpos ; ; multiply negative cx:ax by bx ; neg cx neg ax sbb cx,0 mul bp ; fraction*fraction mov di,dx ; di is low word of result mov ax,cx ; mul bp ; units*fraction add ax,di adc dx,0 neg dx neg ax sbb dx,0 ret ; ; multiply positive cx:ax by bx ; EVEN @@multpos: mul bp ; fraction*fraction mov di,dx ; di is low word of result mov ax,cx ; mul bp ; units*fraction add ax,di adc dx,0 ret ENDP ;============================ ; ; AsmRefresh ; ; ;============================ PROC AsmRefresh PUBLIC AsmRefresh push si push di push bp mov [pixx],0 ;--------------------------------------------------------------------------- ; ; Setup to trace a ray through pixx view pixel ; ; CX : angle of the ray through pixx ; ES : points to segment of finetangent array for this block of code ; ; Upon entrance to initialize block ; ; BX : xpartial ; BP : ypartial ; ;--------------------------------------------------------------------------- EVEN pixxloop: mov ax,SEG finetangent mov es,ax mov cx,[midangle] ; center of view area mov bx,[pixx] shl bx,1 add cx,[pixelangle+bx] ; delta for this pixel cmp cx,0 jge not0 ;---------- ; ; -90 - -1 degree arc ; ;---------- add cx,FINEANGLES ; -90 is the same as 270 jmp entry360 not0: cmp cx,DEG90 jge not90 ;---------- ; ; 0-89 degree arc ; ;---------- entry90: mov [xtilestep],1 ; xtilestep = 1 mov [ytilestep],-1 ; ytilestep = -1 mov [BYTE cs:horizop],OP_JGE ; patch a jge in mov [BYTE cs:vertop],OP_JLE ; patch a jle in mov bx,DEG90-1 sub bx,cx shl bx,2 mov ax,[es:bx] mov dx,[es:bx+2] mov [WORD xstep],ax mov [WORD xstep+2],dx ; xstep = finetangent[DEG90-1-angle] mov bx,cx shl bx,2 mov ax,[es:bx] mov dx,[es:bx+2] neg dx neg ax sbb dx,0 mov [WORD ystep],ax mov [WORD ystep+2],dx ; ystep = -finetangent[angle] mov bx,[xpartialup] ; xpartial = xpartialup mov bp,[ypartialdown] ; ypartial = ypartialdown jmp initvars not90: cmp cx,DEG180 jge not180 ;---------- ; ; 90-179 degree arc ; ;---------- mov ax,-1 mov [xtilestep],ax ; xtilestep = -1 mov [ytilestep],ax ; ytilestep = -1 mov [BYTE cs:horizop],OP_JLE ; patch a jle in mov [BYTE cs:vertop],OP_JLE ; patch a jle in mov bx,cx shl bx,2 mov ax,[es:bx-DEG90*4] mov dx,[es:bx+2-DEG90*4] neg dx neg ax sbb dx,0 mov [WORD xstep],ax mov [WORD xstep+2],dx ; xstep = -finetangent[angle-DEG90] mov bx,DEG180-1 sub bx,cx shl bx,2 mov ax,[es:bx] mov dx,[es:bx+2] neg dx neg ax sbb dx,0 mov [WORD ystep],ax mov [WORD ystep+2],dx ; ystep = -finetangent[DEG180-1-angle] mov bx,[xpartialdown] ; xpartial = xpartialdown mov bp,[ypartialdown] ; ypartial = ypartialdown jmp initvars not180: cmp cx,DEG270 jge not270 ;---------- ; ; 180-269 degree arc ; ;---------- mov [xtilestep],-1 ; xtilestep = -1 mov [ytilestep],1 ; ytilestep = 1 mov [BYTE cs:horizop],OP_JLE ; patch a jle in mov [BYTE cs:vertop],OP_JGE ; patch a jge in mov bx,DEG270-1 sub bx,cx shl bx,2 mov ax,[es:bx] mov dx,[es:bx+2] neg dx neg ax sbb dx,0 mov [WORD xstep],ax mov [WORD xstep+2],dx ; xstep = -finetangent[DEG270-1-angle] mov bx,cx shl bx,2 mov ax,[es:bx-DEG180*4] mov dx,[es:bx+2-DEG180*4] mov [WORD ystep],ax mov [WORD ystep+2],dx ; ystep = finetangent[angle-DEG180] mov bx,[xpartialdown] ; xpartial = xpartialdown mov bp,[ypartialup] ; ypartial = ypartialup jmp initvars not270: cmp cx,DEG360 jge not360 ;---------- ; ; 270-359 degree arc ; ;---------- entry360: mov ax,1 mov [xtilestep],ax ; xtilestep = 1 mov [ytilestep],ax ; ytilestep = 1 mov [BYTE cs:horizop],OP_JGE ; patch a jge in mov [BYTE cs:vertop],OP_JGE ; patch a jge in mov bx,cx shl bx,2 mov ax,[es:bx-DEG270*4] mov dx,[es:bx+2-DEG270*4] mov [WORD xstep],ax mov [WORD xstep+2],dx ; xstep = finetangent[angle-DEG270] mov bx,DEG360-1 sub bx,cx shl bx,2 mov ax,[es:bx] mov dx,[es:bx+2] mov [WORD ystep],ax mov [WORD ystep+2],dx ; ystep = finetangent[DEG360-1-angle] mov bx,[xpartialup] ; xpartial = xpartialup mov bp,[ypartialup] ; ypartial = ypartialup jmp initvars not360: ;---------- ; ; 360-449 degree arc ; ;---------- sub cx,FINEANGLES ; -449 is the same as 89 jmp entry90 ;--------------------------------------------------------------------------- ; ; initialise variables for intersection testing ; ;--------------------------------------------------------------------------- initvars: call NEAR xpartialbyystep ; xpartial is in BX add ax,[WORD viewy] adc dx,[WORD viewy+2] mov [WORD yintercept],ax mov [WORD yintercept+2],dx mov si,[focaltx] add si,[xtilestep] mov [xtile],si ; xtile = focaltx+xtilestep shl si,6 add si,dx ; xspot = (xtile<<6) + yinttile call NEAR ypartialbyxstep ; ypartial is in BP add ax,[WORD viewx] adc dx,[WORD viewx+2] mov [WORD xintercept],ax mov cx,dx mov bx,[focalty] add bx,[ytilestep] mov bp,bx ; ytile = focalty+ytilestep mov di,dx shl di,6 add di,bx ; yspot = (xinttile<<6) + ytile mov bx,[xtile] mov dx,[WORD yintercept+2] mov ax,SCREENSEG mov es,ax ; faster than mov es,[screenseg] ;--------------------------------------------------------------------------- ; ; trace along this angle until we hit a wall ; ; CORE LOOP! ; ; All variables are killed when a wall is hit ; ; AX : scratch ; BX : xtile ; CX : high word of xintercept ; DX : high word of yintercept ; SI : xspot (yinttile<<6)+xtile (index into tilemap and spotvis) ; DI : yspot (xinttile<<6)+ytile (index into tilemap and spotvis) ; BP : ytile ; ES : screenseg ; ;--------------------------------------------------------------------------- ;----------- ; ; check intersections with vertical walls ; ;----------- EVEN vertcheck: cmp dx,bp vertop: ; 0x7e = jle (ytilestep==-1) jle horizentry ; 0x7d = jge (ytilestep==1) vertentry: test [BYTE tilemap+si],0ffh ; tilehit = *((byte *)tilemap+xspot); jnz hitvert passvert: mov [BYTE spotvis+si],1 ; *((byte *)spotvis+xspot) = true; add bx,[xtilestep] ; xtile+=xtilestep mov ax,[WORD ystep] add [WORD yintercept],ax ; yintercept += ystep adc dx,[WORD ystep+2] mov si,bx shl si,6 add si,dx ; xspot = (xtile<<6)+yinttile jmp vertcheck EVEN hitvert: mov al,[BYTE tilemap+si] ; tilehit = *((byte *)tilemap+xspot); mov [BYTE tilehit],al or al,al ; set flags jns notvertdoor jmp vertdoor notvertdoor: mov [WORD xintercept],0 mov [WORD xintercept+2],bx mov [xtile],bx mov [WORD yintercept+2],dx mov [ytile],dx call FAR HitVertWall jmp nextpix ;----------- ; ; check intersections with horizontal walls ; ;----------- EVEN horizcheck: cmp cx,bx horizop: ; 0x7e = jle (xtilestep==-1) jle vertentry ; 0x7d = jge (xtilestep==1) horizentry: test [BYTE tilemap+di],0ffh ; tilehit = *((byte *)tilemap+yspot); jnz hithoriz passhoriz: mov [BYTE spotvis+di],1 ; *((byte *)spotvis+yspot) = true; add bp,[ytilestep] ; ytile+=ytilestep mov ax,[WORD xstep] add [WORD xintercept],ax ; xintercept += xstep adc cx,[WORD xstep+2] mov di,cx shl di,6 add di,bp ; yspot = (xinttile<<6)+ytile jmp horizcheck EVEN hithoriz: mov al,[BYTE tilemap+di] ; tilehit = *((byte *)tilemap+yspot); mov [BYTE tilehit],al or al,al ; set flags js horizdoor mov [WORD xintercept+2],cx mov [xtile],cx mov [WORD yintercept],0 mov [WORD yintercept+2],bp mov [ytile],bp call FAR HitHorizWall jmp nextpix ;--------------------------------------------------------------------------- ; ; next pixel over ; ;--------------------------------------------------------------------------- nextpix: mov ax,[pixx] inc ax mov [pixx],ax cmp ax,[viewwidth] jge done jmp pixxloop done: pop bp pop di pop si retf ;=========================================================================== ;============= ; ; hit a special horizontal wall, so find which coordinate a door would be ; intersected at, and check to see if the door is open past that point ; ;============= horizdoor: mov [xtile],bx ; save off live register variables mov [WORD yintercept+2],dx test al,040h ; both high bits set == pushable wall jnz horizpushwall mov bx,ax and bx,7fh ; strip high bit shl bx,1 ; index into word width door table mov ax,[WORD xstep] mov dx,[WORD xstep+2] sar dx,1 rcr ax,1 ; half a step gets to door position add ax,[WORD xintercept] ; add half step to current intercept pos adc dx,cx ; CX hold high word of xintercept cmp cx,dx ; is it still in the same tile? je hithmid ; ; midpoint is outside tile, so it hit the side of the wall before a door ; continuehoriz: mov bx,[xtile] ; reload register variables mov dx,[WORD yintercept+2] jmp passhoriz ; continue tracing ; ; the trace hit the door plane at pixel position AX, see if the door is ; closed that much ; hithmid: cmp ax,[doorposition+bx] ; position of leading edge of door jb continuehoriz ; ; draw the door ; mov [WORD xintercept],ax ; save pixel intercept position mov [WORD xintercept+2],cx mov [WORD yintercept],8000h ; intercept in middle of tile mov [WORD yintercept+2],bp call FAR HitHorizDoor jmp nextpix ;============ ; ; hit a sliding horizontal wall ; ;============ horizpushwall: mov ax,[WORD xstep+2] ; multiply xstep by pwallmove (0-63) mul [pwallpos] mov bx,ax mov ax,[WORD xstep] mul [pwallpos] add dx,bx sar dx,1 ; then divide by 64 to accomplish a rcr ax,1 ; fixed point multiplication sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 add ax,[WORD xintercept] ; add partial step to current intercept adc dx,cx ; CX hold high word of xintercept cmp cx,dx ; is it still in the same tile? jne continuehoriz ; no, it hit the side ; ; draw the pushable wall at the new height ; mov [WORD xintercept],ax ; save pixel intercept position mov [WORD xintercept+2],dx mov [WORD yintercept+2],bp mov [WORD yintercept],0 call FAR HitHorizPWall jmp nextpix ;=========================================================================== ;============= ; ; hit a special vertical wall, so find which coordinate a door would be ; intersected at, and check to see if the door is open past that point ; ;============= vertdoor: mov [xtile],bx ; save off live register variables mov [WORD yintercept+2],dx test al,040h ; both high bits set == pushable wall jnz vertpushwall mov bx,ax and bx,7fh ; strip high bit shl bx,1 ; index into word width doorposition mov ax,[WORD ystep] mov dx,[WORD ystep+2] sar dx,1 rcr ax,1 ; half a step gets to door position add ax,[WORD yintercept] ; add half step to current intercept pos adc dx,[WORD yintercept+2] cmp [WORD yintercept+2],dx ; is it still in the same tile? je hitvmid ; ; midpoint is outside tile, so it hit the side of the wall before a door ; continuevert: mov bx,[xtile] ; reload register variables mov dx,[WORD yintercept+2] jmp passvert ; continue tracing ; ; the trace hit the door plane at pixel position AX, see if the door is ; closed that much ; hitvmid: cmp ax,[doorposition+bx] ; position of leading edge of door jb continuevert ; ; draw the door ; mov [WORD yintercept],ax ; save pixel intercept position mov [WORD xintercept],8000h ; intercept in middle of tile mov ax,[xtile] mov [WORD xintercept+2],ax call FAR HitVertDoor jmp nextpix ;============ ; ; hit a sliding vertical wall ; ;============ vertpushwall: mov ax,[WORD ystep+2] ; multiply ystep by pwallmove (0-63) mul [pwallpos] mov bx,ax mov ax,[WORD ystep] mul [pwallpos] add dx,bx sar dx,1 ; then divide by 64 to accomplish a rcr ax,1 ; fixed point multiplication sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 sar dx,1 rcr ax,1 add ax,[WORD yintercept] ; add partial step to current intercept adc dx,[WORD yintercept+2] cmp [WORD yintercept+2],dx ; is it still in the same tile? jne continuevert ; no, it hit the side ; ; draw the pushable wall at the new height ; mov [WORD yintercept],ax ; save pixel intercept position mov [WORD yintercept+2],dx mov bx,[xtile] mov [WORD xintercept+2],bx mov [WORD xintercept],0 call FAR HitVertPWall jmp nextpix ENDP END