; Ray/plane intersection for real pitched roofs, including perspective depth.
DrawRoofSlope3D PROC uses ebx esi edi axis:DWORD,x0:DWORD,x1:DWORD,y0:DWORD,y1:DWORD,baseZ:DWORD,rise:DWORD,material:DWORD
    local slope:DWORD,numerator:DWORD,leftPx:DWORD,rightPx:DWORD,topPx:DWORD,bottomPx:DWORD
    local corner:DWORD,wx:DWORD,wy:DWORD,wz:DWORD,visible:DWORD,nearClip:DWORD
    local row:DWORD,column:DWORD,rayZ:DWORD,depth:DWORD,along:DWORD,denominator:DWORD
    local texture:DWORD,textureW:DWORD,textureH:DWORD,light:DWORD,sourceU:DWORD
    invoke ResolveRoofSurface3D,material
    test eax,eax
    jz roof_slope_done
    mov texture,eax
    mov textureW,ecx
    mov textureH,edx
    mov eax,rise
    cdq
    shld edx,eax,16
    shl eax,16
    mov ecx,x1
    sub ecx,x0
    cmp axis,0
    je @F
    mov ecx,y1
    sub ecx,y0
@@:
    idiv ecx
    mov slope,eax
    mov light,242
    test eax,eax
    jns @F
    mov light,184
@@:
    mov eax,playerX
    sub eax,x0
    cmp axis,0
    je @F
    mov eax,playerY
    sub eax,y0
@@:
    imul slope
    shrd eax,edx,16
    neg eax
    add eax,viewEye3D
    sub eax,baseZ
    mov numerator,eax
    mov leftPx,SCREEN_W
    mov rightPx,0
    mov topPx,SCREEN_H
    mov bottomPx,0
    mov visible,0
    mov nearClip,0
    mov corner,0
roof_slope_corner:
    mov eax,x0
    test corner,1
    jz @F
    mov eax,x1
@@:
    mov wx,eax
    mov ebx,y0
    test corner,2
    jz @F
    mov ebx,y1
@@:
    mov wy,ebx
    mov ecx,baseZ
    mov eax,corner
    cmp axis,0
    jne @F
    and eax,1
    jmp roof_slope_corner_height
@@:
    and eax,2
roof_slope_corner_height:
    test eax,eax
    jz @F
    add ecx,rise
@@:
    mov wz,ecx
    invoke ProjectCityPoint3D,wx,wy
    cmp edx,4096
    jg roof_slope_projected_corner
    mov nearClip,1
    jmp roof_slope_corner_next
roof_slope_projected_corner:
    inc visible
    mov esi,edx
    cmp eax,leftPx
    jge @F
    mov leftPx,eax
@@:
    cmp eax,rightPx
    jle @F
    mov rightPx,eax
@@:
    mov eax,viewEye3D
    sub eax,wz
    mov ecx,SCREEN_H
    imul ecx
    idiv esi
    add eax,viewHorizon3D
    cmp eax,topPx
    jge @F
    mov topPx,eax
@@:
    cmp eax,bottomPx
    jle @F
    mov bottomPx,eax
@@:
roof_slope_corner_next:
    inc corner
    cmp corner,4
    jb roof_slope_corner
    cmp visible,0
    je roof_slope_done
    cmp nearClip,0
    je @F
    mov leftPx,0
    mov rightPx,SCREEN_W-1
    mov topPx,0
    mov bottomPx,SCREEN_H-1
@@:
    cmp leftPx,0
    jge @F
    mov leftPx,0
@@:
    cmp rightPx,SCREEN_W-1
    jle @F
    mov rightPx,SCREEN_W-1
@@:
    cmp topPx,0
    jge @F
    mov topPx,0
@@:
    cmp bottomPx,SCREEN_H-1
    jle @F
    mov bottomPx,SCREEN_H-1
@@:
    mov eax,leftPx
    cmp eax,rightPx
    jge roof_slope_done
    mov eax,topPx
    cmp eax,bottomPx
    jge roof_slope_done
    mov row,eax
    mov ebx,leftPx
roof_slope_prepare:
    mov eax,cityRayX3D[ebx*4]
    cmp axis,0
    je @F
    mov eax,cityRayY3D[ebx*4]
@@:
    imul slope
    shrd eax,edx,16
    mov roofSlopeRay3D[ebx*4],eax
    inc ebx
    cmp ebx,rightPx
    jbe roof_slope_prepare
roof_slope_row:
    mov eax,viewHorizon3D
    sub eax,row
    shl eax,16
    cdq
    mov ecx,SCREEN_H
    idiv ecx
    mov rayZ,eax
    mov eax,row
    imul eax,SCREEN_W*4
    mov ebx,leftPx
    lea edi,[eax+ebx*4]
    mov column,ebx
roof_slope_pixel:
    mov ebx,column
    mov ecx,roofSlopeRay3D[ebx*4]
    sub ecx,rayZ
    mov denominator,ecx
    mov eax,ecx
    cdq
    xor eax,edx
    sub eax,edx
    cmp eax,64
    jb roof_slope_advance
    shl eax,10
    mov along,eax
    mov eax,numerator
    cdq
    xor eax,edx
    sub eax,edx
    cmp eax,along
    jae roof_slope_advance
    mov eax,numerator
    cdq
    shld edx,eax,16
    shl eax,16
    idiv denominator
    cmp eax,4096
    jle roof_slope_advance
    cmp eax,cityDepthBuffer3D[edi]
    jae roof_slope_advance
    mov depth,eax
    imul cityRayX3D[ebx*4]
    shrd eax,edx,16
    add eax,playerX
    cmp eax,x0
    jl roof_slope_advance
    cmp eax,x1
    jge roof_slope_advance
    mov wx,eax
    sub eax,x0
    sar eax,9
    mov ecx,textureW
    dec ecx
    and eax,ecx
    mov sourceU,eax
    mov eax,depth
    imul cityRayY3D[ebx*4]
    shrd eax,edx,16
    add eax,playerY
    cmp eax,y0
    jl roof_slope_advance
    cmp eax,y1
    jge roof_slope_advance
    mov wy,eax
    cmp roofSlopeMask3D,0
    je roof_slope_sample
    mov eax,wx
    sub eax,roofSlopeCentreX3D
    cdq
    xor eax,edx
    sub eax,edx
    imul roofSlopeHalfY3D
    shrd eax,edx,16
    mov along,eax
    mov eax,wy
    sub eax,roofSlopeCentreY3D
    cdq
    xor eax,edx
    sub eax,edx
    imul roofSlopeHalfX3D
    shrd eax,edx,16
    cmp roofSlopeMask3D,1
    jne @F
    cmp eax,along
    ja roof_slope_advance
    jmp roof_slope_sample
@@:
    cmp eax,along
    jb roof_slope_advance
roof_slope_sample:
    mov eax,wy
    sub eax,y0
    sar eax,9
    mov ecx,textureH
    dec ecx
    and eax,ecx
    imul eax,textureW
    add eax,sourceU
    mov esi,texture
    mov eax,[esi+eax*4]
    invoke ShadeRoofCityPixel3D,eax,depth,light,material
    mov ecx,edi
    shr ecx,2
    mov edx,roofPixelGlow3D
    mov roofGlowMask3D[ecx],dl
    mov screenBuffer[edi],eax
    mov eax,depth
    mov cityDepthBuffer3D[edi],eax
    mov eax,edi
    shr eax,2
    mov roofCityMask3D[eax],1
roof_slope_advance:
    add edi,4
    inc column
    mov eax,column
    cmp eax,rightPx
    jbe roof_slope_pixel
    inc row
    mov eax,row
    cmp eax,bottomPx
    jbe roof_slope_row
roof_slope_done:
    ret
DrawRoofSlope3D ENDP

DrawRoofPyramid3D PROC uses ebx esi centreX:DWORD,centreY:DWORD,baseZ:DWORD,halfX:DWORD,halfY:DWORD,height:DWORD,mat:DWORD
    local x0:DWORD,x1:DWORD,y0:DWORD,y1:DWORD,topZ:DWORD,down:DWORD
    mov eax,centreX
    mov roofSlopeCentreX3D,eax
    sub eax,halfX
    mov x0,eax
    mov eax,centreX
    add eax,halfX
    mov x1,eax
    mov eax,centreY
    mov roofSlopeCentreY3D,eax
    sub eax,halfY
    mov y0,eax
    mov eax,centreY
    add eax,halfY
    mov y1,eax
    mov eax,halfX
    mov roofSlopeHalfX3D,eax
    mov eax,halfY
    mov roofSlopeHalfY3D,eax
    mov eax,baseZ
    add eax,height
    mov topZ,eax
    mov eax,height
    neg eax
    mov down,eax
    mov roofSlopeMask3D,1
    invoke DrawRoofSlope3D,0,x0,centreX,y0,y1,baseZ,height,mat
    invoke DrawRoofSlope3D,0,centreX,x1,y0,y1,topZ,down,mat
    mov roofSlopeMask3D,2
    invoke DrawRoofSlope3D,1,x0,x1,y0,centreY,baseZ,height,mat
    invoke DrawRoofSlope3D,1,x0,x1,centreY,y1,topZ,down,mat
    mov roofSlopeMask3D,0
    ret
DrawRoofPyramid3D ENDP