ack3d/ack_lib/ACKRTN3.ASM

IDEAL
JUMPS
P386
P387            ; Allow 386 processor

model flat

codeseg

include "ackrtn.inc"

extrn   _gMultiWalls:word
extrn   _WallDistTable:dword
extrn   _BackDropRows:dword
extrn   _FloorCeilRtn:dword
extrn   _Resolution:word
extrn   _ScreenOffset:word
extrn   _bmDistance:dword
extrn   _bmWall:dword
extrn   _scPtr:dword
extrn   _VidTop:dword
extrn   _VidBottom:dword
extrn   _Floors1:dword
extrn   _Floors2:dword
extrn   _PlayerAngle:word
extrn   _BackArray:dword
extrn   _gWinStartX:word
extrn   _gWinStartY:word
extrn   _gWinEndX:word
extrn   _gWinEndY:word
extrn   _gWinHeight:word
extrn   _gWinWidth:word
extrn   _gCenterRow:word
extrn   _gCenterOff:word

extrn   _scVid:dword
extrn   _scWall:dword
extrn   _scPal:dword
extrn   _scdst:word
extrn   _scwht:word
extrn   _scmulti:word
extrn   _sctopht:word
extrn   _scbotht:word
extrn   _scsavwht:word
extrn   _scmulcnt:word
extrn   _scsavVid:dword
extrn   _scbNum:word
extrn   _scMulData:dword
extrn   _scColumn:dword
extrn   _WallbMaps:dword

extrn   _FloorMap:word
extrn   _CeilMap:word
extrn   _LastWallHeight:word
extrn   _ViewAngle:word
extrn   _ScreenOffset:word
extrn   _xPglobal:dword
extrn   _yPglobal:dword
extrn   _xBegGlobal:dword
extrn   _yBegGlobal:dword
extrn   _aeGlobal:dword
extrn   _xGridGlobal:dword
extrn   _yGridGlobal:dword
extrn   _xPglobalHI:dword
extrn   _yPglobalHI:dword
extrn   _rbaTable:dword
extrn   _rsHandle:dword
extrn   _LastX1:dword
extrn   _LastY1:dword
extrn   _iLastX:dword
extrn   _iLastY:dword
extrn   _MaxDistance:word
extrn   _ErrorCode:word
extrn   _xMapPosn:dword
extrn   _yMapPosn:dword
extrn   _Grid:dword
extrn   _ObjGrid:dword
extrn   _ViewHeight:word
extrn   _CeilingHeight:word
extrn   _gTopColor:byte
extrn   _gBottomColor:byte
extrn   _PlayerAngle:word
extrn   _gScrnBuffer:dword
extrn   _gBkgdBuffer:dword
extrn   _gCenterOff:word
extrn   _gWinHeight:word
extrn   _SysFlags:word


extrn   _xSecretmPos:word
extrn   _xSecretmPos1:word
extrn   _xSecretColumn:word

extrn   _ySecretmPos:word
extrn   _ySecretmPos1:word
extrn   _ySecretColumn:word

extrn   _TotalSecret:word
extrn   _ViewColumn:word
extrn   _SinTable:dword
extrn   _CosTable:dword
extrn   _LongTanTable:dword
extrn   _LongInvTanTable:dword
extrn   _InvCosTable:byte
extrn   _InvSinTable:byte
extrn   _LongCosTable:dword
extrn   _ViewCosTable:dword
extrn   _xNextTable:dword
extrn   _yNextTable:dword

extrn   _LastMapPosn:word
extrn   _LastObjectHit:word
extrn   _TotalObjects:word
extrn   _FoundObjectCount:word
extrn   _ObjectsSeen:byte
extrn   _MoveObjectCount:word
extrn   _MoveObjectList:byte
extrn   _ObjNumber:byte
extrn   _ObjRelDist:byte
extrn   _ObjColumn:byte

extrn   _x_xPos:dword
extrn   _x_yPos:dword
extrn   _x_xNext:dword
extrn   _x_yNext:dword
extrn   _y_xPos:dword
extrn   _y_yPos:dword
extrn   _y_xNext:dword
extrn   _y_yNext:dword

extrn   _Slice:dword
extrn   _sPtr:dword
extrn   _HitMap:byte

extrn   xRaySetup_:near
extrn   yRaySetup_:near
extrn   BuildSlice_:near
extrn   xRayCast_:near
extrn   yRayCast_:near
extrn   AckDrawFloor_:near
extrn   AckDrawFloorOnly_:near
extrn   AckDrawCeilingOnly_:near
extrn   DrawWalls_:near
extrn   CheckDoors_:near
extrn   BuildSliceMulti_:near
extrn   FindObject_:near

public xRayCastMulti_
public yRayCastMulti_
public ShowColLow_
public ShowColMaskLow_
public BuildUpView_

align 2
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; void ShowColLow(void)
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proc ShowColLow_ near
        push    ebp
        push    esi
        push    edi
        mov     ebp,eax
        mov     [_scPtr],eax
        mov     edi,[_scVid]
        mov     edx,[_scPal]
        mov     ax,[_scwht]
        mov     [_scsavwht],ax
        movsx   ecx,[_sctopht]
        mov     ebx,[_scWall]
        add     ebx,ecx
        mov     [_bmWall],ebx
        mov     ch,al
        inc     ch
        mov     eax,0
        mov     ebx,0

;--TEST------------------------------------------------------------------------
        test    [word ptr _scbNum],WALL_TYPE_UPPER
        jz      short toprun
        mov     ebp,[_bmDistance]

zztoploop:
        dec     ch
        jz      short zzdomulti
        add     bx,bp
        cmp     bh,cl
        jge     short zzdomulti
        sub     di,320
        jmp     zztoploop

zzdomulti:
        mov     ebp,[_scPtr]
        mov     [_scwht],cx
        mov     [_scsavVid],edi
        jmp     chkmulti

;--TEST------------------------------------------------------------------------
toprun:
        mov     ebp,[_bmDistance]

toploop:
        movsx   eax,bh
        mov     esi,[_bmWall]
        sub     esi,eax
        mov     al,[esi]
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax
        add     bx,bp
        cmp     bh,cl
        jg      short botrun
        dec     ch
        jz      short botrun
        sub     edi,320
        jmp     toploop

botrun:
        mov     ebp,[_scPtr]
        mov     [_scwht],cx
        mov     [_scsavVid],edi
        mov     [_VidTop],edi
        mov     edi,[_scVid]
        mov     cx,[_scbotht]
        mov     bx,[_scsavwht]
        mov     ch,bl
        mov     ebx,0
        mov     esi,[_bmWall]
        inc     esi
        mov     ebp,[_bmDistance]
        dec     cl

botloop:
        add     edi,320
        movsx   ax,bh
        mov     al,[esi+eax]
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax
        dec     ch
        jz      short chkmulti
        add     bx,bp
        cmp     bh,cl
        jl      botloop

chkmulti:
        mov     [_VidBottom],edi
        mov     ebp,[_scPtr]
        mov     edi,[_scsavVid]
        cmp     [word ptr _scmulti],0
        jz      alldone
        mov     cx,[_scmulcnt]

        mov     ebx,[_scMulData]        ;ptr to count and wall data
        mov     cl,[ebx]                ;get count of data
        inc     ebx
        mov     al,[ebx]                ;first wall to show
        inc     ebx
        mov     [_scMulData],ebx
        movsx   ebx,al                  ;get wall number
        shl     ebx,2                   ;x4 for index into wall bitmap array
        mov     eax,[_WallbMaps]
        mov     ebx,[eax+ebx]
        add     ebx,[dword ptr _scColumn]   ;add in current column
        add     ebx,63                  ;point to bottom of column
        mov     [_bmWall],ebx

        mov     bx,[_scwht]
        mov     ch,bh
        cmp     ch,0
        jz      short alldone

        mov     ebx,0
        mov     ebp,[_bmDistance]

mulloop:
        sub     edi,320
        movsx   eax,bh
        mov     esi,[_bmWall]
        sub     esi,eax
        mov     al,[esi]
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax
        dec     ch
        jz      short alldone
        add     bx,bp
        cmp     bh,64
        jge     short nextlevel
        jmp     mulloop

nextlevel:
        dec     cl
        jz      short alldone
        mov     ebx,[_scMulData]
        mov     al,[ebx]            ;next wall number
        inc     ebx
        mov     [_scMulData],ebx
        movsx   ebx,al
        shl     ebx,2
        mov     eax,[_WallbMaps]
        mov     ebx,[eax+ebx]
        add     ebx,[dword ptr _scColumn]   ;add in current column
        add     ebx,63                  ;point to bottom of column
        mov     [_bmWall],ebx
        mov     ebx,0
        jmp     mulloop

alldone:
        mov     [_VidTop],edi
        pop     edi
        pop     esi
        pop     ebp
        ret
        endp


align 2
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; void ShowColMaskLow(void)
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
proc ShowColMaskLow_ near
        push    ebp
        push    esi
        push    edi
        mov     ebp,eax
        mov     [_scPtr],eax
        mov     edi,[_scVid]
        mov     edx,[_scPal]
        mov     ax,[_scwht]
        mov     [_scsavwht],ax
        movsx   ecx,[_sctopht]
        mov     ebx,[_scWall]
        add     ebx,ecx
        mov     [_bmWall],ebx
        mov     ch,al
        mov     eax,0
        mov     ebx,0

;--TEST------------------------------------------------------------------------
        test    [word ptr _scbNum],WALL_TYPE_UPPER
        jz      short m_toprun
        mov     ebp,[_bmDistance]

m_zztoploop:
        dec     ch
        jz      short m_zzdomulti
        add     bx,bp
        cmp     bh,cl
        jge     short m_zzdomulti
        sub     edi,320
        jmp     m_zztoploop

m_zzdomulti:
        mov     ebp,[_scPtr]
        mov     [_scwht],cx
        mov     [_scsavVid],edi
        jmp     m_chkmulti

;--TEST------------------------------------------------------------------------
m_toprun:
        mov     ebp,[_bmDistance]

m_toploop:
        movsx   eax,bh
        mov     esi,[_bmWall]
        sub     esi,eax
        mov     al,[esi]
        or      al,al
        jz      m_blank1
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax

m_blank1:
        add     bx,bp
        cmp     bh,cl
        jg      short m_botrun
        dec     ch
        jz      short m_botrun
        sub     edi,320
        jmp     m_toploop

m_botrun:
        mov     ebp,[_scPtr]
        mov     [_scwht],cx
        mov     [_scsavVid],edi
        mov     edi,[_scVid]
        mov     cx,[_scbotht]
        mov     bx,[_scsavwht]
        mov     ch,bl
        mov     ebx,0
        mov     esi,[_bmWall]
        inc     esi
        mov     ebp,[_bmDistance]

m_botloop:
        add     edi,320
        movsx   ax,bh
        mov     al,[esi+eax]
        or      al,al
        jz      m_blank2
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax

m_blank2:
        dec     ch
        jz      short m_chkmulti
        add     bx,bp
        cmp     bh,cl
        jl      m_botloop

m_chkmulti:
        mov     ebp,[_scPtr]
        cmp     [word ptr _scmulti],0
        jz      short m_alldone
        mov     cx,[_scmulcnt]
        mov     bx,[_scwht]
        mov     ch,bh
        cmp     ch,0
        jz      short m_alldone

        mov     edi,[_scsavVid]
        mov     ebx,[_scWall]
        add     ebx,63
        mov     [_bmWall],ebx
        mov     ebx,0
        mov     ebp,[_bmDistance]

m_mulloop:
        sub     edi,320
        movsx   eax,bh
        mov     esi,[_bmWall]
        sub     esi,eax
        mov     al,[esi]
        or      al,al
        jz      m_blank3
        mov     al,[edx+eax]
        mov     ah,al
        mov     [edi],ax

m_blank3:
        dec     ch
        jz      short m_alldone
        add     bx,bp
        cmp     bh,64
        jge     short m_nextlevel
        jmp     m_mulloop

m_nextlevel:
        mov     ebx,0
        dec     cl
        jnz     m_mulloop

m_alldone:
        pop     edi
        pop     esi
        pop     ebp
        ret
        endp

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; USHORT xRayCastMulti(void)
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
proc xRayCastMulti_ near
;         sub        esp,50
         push    esi
         push    edi
         push    ebx
         push    ecx
    push    edx

    mov     [word ptr retval],0

looptop:

    mov     edx,[dword ptr _x_xPos]
    cmp     edx,large 0
    jl      short getout
    cmp     edx,large 4096
    jg      short getout
    mov     eax,[_x_yPos]
    cmp     eax,large 0
    jl      short getout
    cmp     eax,large 010000000h
    jle     short inbounds

getout:
    jmp     loopdone

inbounds:
         sar        eax,16
    and     ax,-64
         sar        edx,6
    add     ax,dx
    mov     si,ax

    shl     ax,1
    movsx   eax,ax
    mov     ebx,[dword ptr _ObjGrid]
    mov     ax,[word ptr ebx+eax]
    or      ax,ax
    jz      short no_obj

    and     ax,0FFh
    mov     [word ptr Color],ax

    movsx   ecx,[_FoundObjectCount]     ;// Get number of current objects seen
    mov     ebx,ecx
    jcxz    short nofound               ;// None found yet, add this new one
    mov     edi,offset _ObjectsSeen
    repne   scasb                       ;// See if this object already seen
    jz      short no_obj                ;// Yes, ignore this ray then

nofound:
    mov     edi,offset _ObjectsSeen
    mov     [edi+ebx],al
    inc     bx
    mov     [word ptr _FoundObjectCount],bx

no_obj:
         movsx   eax,si

         shl        eax,1
    mov     ebx,[dword ptr _xGridGlobal]
    mov     cx,[ebx+eax]
    or      cx,cx
    jz      short next_square
    test    cx,WALL_UPPER_MULTI
    jz      short next_square
    cmp     cl,[byte ptr _LastWallHeight]
    jbe     short next_square

    mov     [word ptr _xMapPosn],si
    mov     ebx,[dword ptr _x_xPos]
    mov     [dword ptr _iLastX],ebx
    mov     edx,[dword ptr _x_yPos]
    mov     [dword ptr _LastY1],edx

    movsx   eax,cx
    jmp     short xRayDone

next_square:
    mov     eax,[dword ptr _x_xNext]
    add     [dword ptr _x_xPos],eax
    mov     eax,[dword ptr _x_yNext]
    add     [dword ptr _x_yPos],eax
    jmp     looptop

loopdone:
    movsx   eax,[word ptr retval]

xRayDone:
         pop        edx
         pop        ecx
         pop        ebx
         pop        edi
         pop        esi
         ret
         endp

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; USHORT yRayCastMulti(void)
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
proc yRayCastMulti_ near
;         sub        esp,50
         push    esi
         push    edi
         push    ebx
         push    ecx
         push    edx
         mov        [word ptr retval],0

y_looptop:
    mov     edx,[dword ptr _y_xPos]
    cmp     edx,large 0
         jl         short y_getout
    cmp     edx,large 010000000h
    jg      short y_getout
    mov     eax,[_y_yPos]
    cmp     eax,large 0
    jl      short y_getout
    cmp     eax,large 4096
    jle     short y_inbounds

y_getout:
    jmp     loopdone

y_inbounds:
    sar     edx,22
    and     ax,-64
    add     ax,dx
    mov     si,ax

    shl     ax,1
    movsx   eax,ax
    mov     ebx,[dword ptr _ObjGrid]
    mov     ax,[ebx+eax]
    or      ax,ax
    jz      short y_no_obj

    and     ax,0FFh
    mov     [word ptr Color],ax

    movsx   ecx,[_FoundObjectCount]
    mov     ebx,ecx
         jcxz    short y_nofound
    mov     edi,offset _ObjectsSeen
    repne   scasb
    jz      short y_no_obj

y_nofound:
    mov     edi,offset _ObjectsSeen
    mov     [edi+ebx],al
    inc     bx
    mov     [word ptr _FoundObjectCount],bx

y_no_obj:
    movsx   eax,si

    shl     eax,1
    mov     ebx,[dword ptr _yGridGlobal]
    mov     cx,[ebx+eax]
         or         cx,cx
    jz      short y_next_square

y_wall_here:
    test    cx,WALL_UPPER_MULTI
    jz      short y_next_square
    cmp     cl,[byte ptr _LastWallHeight]
    jbe     short y_next_square
    mov     [word ptr _yMapPosn],si
    mov     ebx,[dword ptr _y_xPos]
    mov     [dword ptr _LastX1],ebx
    mov     edx,[dword ptr _y_yPos]
    mov     [dword ptr _iLastY],edx
         mov        edx,ebx

    movsx   eax,cx
    jmp     short yRayDone

y_next_square:
    mov     eax,[dword ptr _y_xNext]
    add     [dword ptr _y_xPos],eax
    mov     eax,[dword ptr _y_yNext]
    add     [dword ptr _y_yPos],eax
    jmp     y_looptop

y_loopdone:
    movsx   eax,[word ptr retval]

yRayDone:
    pop     edx
         pop        ecx
         pop        ebx
         pop        edi
         pop        esi
         ret
         endp


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; void CheckHitMap(void)
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proc CheckHitMap_ near
        mov     edi,offset _HitMap
        mov     edx,edi
        mov     ecx,4096
    mov esi,[dword ptr _ObjGrid]

chmLoop:
        xor     eax,eax
        repe    scasb
        jcxz    chmDone
        mov     ebx,edi     ;get current location
        sub     ebx,edx     ;minus start for actual offset
        dec     ebx         ;minus base 0 offset
        shl     ebx,1       ;times 2 for word array
        mov     ax,[word ptr esi+ebx]
        or      al,al       ;is there an object there?
        jz      chmLoop     ;nope, keep checking
        movzx   ebx,[word ptr _FoundObjectCount]
        mov     [byte ptr _ObjectsSeen+ebx],al
        inc     ebx
        mov     [word ptr _FoundObjectCount],bx
        jmp     chmLoop

chmDone:
        ret
        endp

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; void BuildUpView(void)
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proc BuildUpView_ near
        push    ebp     ; Save registers used by this routine
        push    esi
        push    edi
        push    ebx
        push    ecx
        push    edx

        call CheckDoors_      ; Determine the state of the doors used in the view

        mov     edi,offset _HitMap      ; Access the hit map
        mov     ecx,1024                ; Size of the hit map
        xor     eax,eax                 ; Clear each location
        rep     stosd                   ; Clear out entire hit map

; Check to see if moveable objects are found in the view. If so, access the object list
; and store the objects.
        mov     [word ptr _MaxDistance],0
        movzx   ecx,[word ptr _MoveObjectCount] ; Get # of moveable objects
        mov     [_FoundObjectCount],cx          ; Store # of objects found in view
        jcxz    short buv010                    ; No objects are used, jump ahead
        mov     edi,offset _ObjectsSeen         ; Reference global object list
        mov     esi,offset _MoveObjectList      ; List of movable objects
        mov     ebx,ecx                         ; # of moveable objects
        sar     ecx,2                           ; Divide by 2
        rep     movsd
        mov     ecx,ebx                         ; # of moveable objects
        and     ecx,3
        rep     movsb                           ; Finish copying _ObjectSeen to
                                                ; _MoveObjectList
buv010:
        movzx   esi,[_gWinEndX]         ; Get right side of viewport
        cmp     si,320                  ; Is right coord. = 320?
        jae     short buv020
        inc     esi                     ; Adjust right viewport if not 320

buv020:
        movzx   eax,[_PlayerAngle]      ; Get current player<65>s angle
        sub     eax,INT_ANGLE_32        ; Check with 32 degree point
        jnc     short buv030            ; Skip if in range
        add     eax,INT_ANGLE_360       ; Add 360 degrees to angle

buv030:
        movzx   ebx,[_gWinStartX]       ; Get left side of viewport
        mov     [_ViewColumn],bx        ; Save location in _ViewColumn
        add     eax,ebx                 ; Add angle to left side
        cmp     eax,INT_ANGLE_360       ; Are we out of range?
        jl      short buv040            ; We<57>re ok!
        sub     eax,INT_ANGLE_360       ; Reduce angle by 360 degrees

buv040:
        mov     [_ViewAngle],ax         ; Store updated angle

; The start of the main loop that builds individual slices for the view.
; This loop continues until the entire view has been built. Each time through
; the loop, the player<65>s viewing angle is increased. This continues until a full
; 64 degre range is casted (assuming a full width screen is used).
buv050:
        movzx   ebx,[_ViewColumn]               ; Get left column position
        mov     [dword ptr _WallDistTable+ebx*4],4096   ; Max distance to walls
        mov     eax,offset _Slice               ; Access base adress of Slice structure
        imul    ebx,saSize                      ; Calculate offset into actual slice
        add     eax,ebx                         ; Add offset to base address
        mov     [_sPtr],eax                     ; Set up pointer to actual column slice
        movzx   edi,[_ViewAngle]                ; Use current viewing angle
        call xRaySetup_                       ; Set up x ray to start casting

buv060:
        call yRaySetup_                       ; Set up y ray to start casting

buv070:
        mov     [word ptr _LastWallHeight],0    ; For checking mult-height walls
        call BuildSlice_                      ; Build the current slice
        cmp     [word ptr _gMultiWalls],0       ; Are multi-height walls used?
        jz      short buv080                    ; Nope, no need to check

        cmp     [word ptr _LastWallHeight],200  ; No need to check if > 200
        jg      short buv080

        mov     eax,[_sPtr]                     ; Get base address of column slice
        cmp     [dword ptr eax+saNext],0        ; Check for any more walls
        je      short buv080
        cmp     [word ptr eax+saDist],96        ; Distance from POV to slice is
        jle     short buv080                    ; less than or equal to 96

        call BuildSliceMulti_                   ; Build the current slice for
                                                ; a multi-height wall
buv080:
        movzx   eax,[_ViewColumn]               ; Get current column
        inc     eax                             ; Advance to the next column
        inc     edi                             ; Increment the casting angle
        cmp     [word ptr _Resolution],RES_LOW  ; Check for screen resolution
        jne     short buv090
        inc     edi                             ; Increment angle and position
        inc     eax                             ; for higher resolution casting

buv090:
        cmp     edi,INT_ANGLE_360               ; Did we go past 360 degrees?
        jl      short buv100                    ; We<57>re ok
        sub     edi,INT_ANGLE_360               ; Adjust angle for building next slice

buv100:
        mov     [_ViewAngle],di         ; Save current viewing angle
        mov     [_ViewColumn],ax        ; Save column position
        cmp     eax,esi                 ; Are we done yet?
        jl      buv050                  ; Nope; go build next slice

buv_exit:
        call CheckHitMap_
        call FindObject_              ; Update slice structures with objects found
        call [dword ptr _FloorCeilRtn]       ; Build the floor and ceiling
        call DrawWalls_                        ; Build the walls

        pop     edx     ; Restore the registers used
        pop     ecx
        pop     ebx
        pop     edi
        pop     esi
        pop     ebp
        ret
        endp

        end