; Hysteresis and a hold timer keep the shared doorway safe on both sides.
UpdateBasementDoor3D PROC uses ebx
    local nearDoor:DWORD,rangeX:DWORD,rangeY:DWORD
    mov nearDoor,0
    mov rangeX,FP_1*12/5
    mov rangeY,FP_1*7/5
    mov eax,basementDoorTarget3D
    or eax,basementDoorOpen3D
    or eax,basementWheelTime3D
    jz @F
    mov rangeX,3*FP_1
    mov rangeY,FP_1*9/5
@@:
    cmp engineMode,MODE_WALK
    jne steel_approach_stairs
    cmp hallLevel3D,0
    jne steel_door_clock
    mov eax,playerX
    sub eax,FP_1*289/10
    cdq
    xor eax,edx
    sub eax,edx
    cmp eax,rangeX
    ja steel_door_clock
    mov eax,playerY
    sub eax,FP_1*105/10
    cdq
    xor eax,edx
    sub eax,edx
    cmp eax,rangeY
    ja steel_door_clock
    jmp steel_request_open
steel_approach_stairs:
    cmp engineMode,MODE_STAIRS
    jne steel_door_clock
    cmp stairRoute3D,1
    jne steel_door_clock
    mov eax,5*FP_1
    cmp rangeX,3*FP_1
    jne @F
    mov eax,FP_1*13/2
@@:
    cmp playerX,eax
    ja steel_door_clock
    cmp playerY,FP_1*195/10
    jb steel_door_clock
    cmp playerY,FP_1*235/10
    ja steel_door_clock
steel_request_open:
    mov nearDoor,1
    mov basementDoorTarget3D,FP_1
    mov basementDoorHold3D,1200
steel_door_clock:
    mov eax,animationClock3D
    cmp eax,interiorDoorClock3D
    je steel_update_done
    mov interiorDoorClock3D,eax
    mov ebx,deltaTime3D
    cmp ebx,100
    jbe @F
    mov ebx,100
@@:
    cmp nearDoor,1
    je steel_animate
    ; A manual E request outside the automatic opening radius still gets time.
    cmp basementDoorTarget3D,FP_1
    jne steel_far_hold
    cmp basementDoorHold3D,0
    jne steel_far_hold
    mov eax,basementDoorOpen3D
    or eax,basementWheelTime3D
    jnz steel_far_hold
    mov basementDoorHold3D,2000
steel_far_hold:
    cmp basementDoorHold3D,0
    je steel_request_close
    mov eax,basementDoorHold3D
    sub eax,ebx
    jae @F
    xor eax,eax
@@:
    mov basementDoorHold3D,eax
    jmp steel_animate
steel_request_close:
    mov basementDoorTarget3D,0
steel_animate:
    cmp basementDoorTarget3D,0
    je steel_close_leaf
    cmp basementWheelTime3D,700
    jae steel_swing
    mov eax,700
    sub eax,basementWheelTime3D
    cmp ebx,eax
    jb steel_wheel_partial
    sub ebx,eax
    mov basementWheelTime3D,700
    jmp steel_swing
steel_wheel_partial:
    add basementWheelTime3D,ebx
    jmp steel_update_done
steel_swing:
    ; Opening: unlock first, then swing around the fixed hinge over 1000ms.
    imul eax,ebx,FP_1
    xor edx,edx
    mov ecx,1000
    div ecx
    add eax,basementDoorOpen3D
    cmp eax,FP_1
    jbe @F
    mov eax,FP_1
@@:
    mov basementDoorOpen3D,eax
    jmp steel_update_done
steel_close_leaf:
    cmp basementDoorOpen3D,0
    je steel_lock_wheel
    ; Carry unused milliseconds into locking only after the leaf is fully shut.
    imul eax,basementDoorOpen3D,1000
    add eax,FP_1-1
    shr eax,16
    cmp ebx,eax
    jb steel_close_partial
    sub ebx,eax
    mov basementDoorOpen3D,0
    jmp steel_lock_wheel
steel_close_partial:
    imul eax,ebx,FP_1
    xor edx,edx
    mov ecx,1000
    div ecx
    sub basementDoorOpen3D,eax
    jmp steel_update_done
steel_lock_wheel:
    mov eax,basementWheelTime3D
    sub eax,ebx
    jae @F
    xor eax,eax
@@:
    mov basementWheelTime3D,eax
steel_update_done:
    ret
UpdateBasementDoor3D ENDP

; The shared doorway occupies the overlapping landing in both local maps.
StairDoorCanWalk3D PROC px:DWORD,py:DWORD
    cmp stairRoute3D,1
    jne stair_steel_clear
    cmp px,FP_1*35/10
    jb stair_steel_clear
    cmp px,FP_1*42/10
    ja stair_steel_clear
    cmp py,FP_1*2025/100
    jb stair_steel_blocked
    cmp py,FP_1*2175/100
    jae stair_steel_blocked
    mov eax,px
    add eax,25*FP_1
    mov edx,py
    sub edx,FP_1*21/2
    invoke InteriorDoorCanWalk3D,eax,edx
    ret
stair_steel_blocked:
    xor eax,eax
    ret
stair_steel_clear:
    mov eax,1
    ret
StairDoorCanWalk3D ENDP

RenderStairDoor3D PROC
    local oldX:DWORD,oldY:DWORD,oldEye:DWORD
    cmp stairRoute3D,1
    jne stair_steel_done
    ; Fill the wider landing around the actual narrow doorway on the stair side.
    invoke DrawCityBoxSides3D,FP_1*375/100,4*FP_1,20*FP_1,FP_1*2025/100,FP_1*3/2,FP_1*37/10,92
    invoke DrawCityBoxSides3D,FP_1*375/100,4*FP_1,FP_1*2175/100,23*FP_1,FP_1*3/2,FP_1*37/10,92
    mov eax,playerX
    mov oldX,eax
    add playerX,25*FP_1
    mov eax,playerY
    mov oldY,eax
    sub playerY,FP_1*21/2
    mov eax,viewEye3D
    mov oldEye,eax
    sub viewEye3D,FP_1*3/2
    invoke DrawCityVertical3D,0,FP_1*2838/100,9*FP_1,12*FP_1,-FP_1/10,FP_1*21/10,131
    call DrawBasementLeaf3D
    mov eax,oldX
    mov playerX,eax
    mov eax,oldY
    mov playerY,eax
    mov eax,oldEye
    mov viewEye3D,eax
stair_steel_done:
    ret
RenderStairDoor3D ENDP

; Perspective-correct vertical plane with a rotating horizontal basis. The wheel
; is baked into offline texture phases, not rotated in screen space at runtime.
DrawBasementLeaf3D PROC uses ebx esi edi
    local ux:DWORD,uy:DWORD,nx:DWORD,ny:DWORD,numerator:DWORD
    local depth:DWORD,texture:DWORD,sourceX:DWORD,top:DWORD,bottom:DWORD
    local stepY:DWORD,sourceY:DWORD,row:DWORD,column:DWORD,destination:DWORD
    invoke ResolveUpperMaterial3D,128
    test eax,eax
    jz steel_leaf_done
    mov texture,eax
    mov eax,basementDoorOpen3D
    imul eax,128
    shr eax,16
    and eax,511
    mov ecx,tableSin[eax*4]
    mov ux,ecx
    neg ecx
    mov ny,ecx
    mov ecx,tableCos[eax*4]
    mov uy,ecx
    mov nx,ecx
    mov eax,FP_1*289/10
    sub eax,playerX
    imul nx
    shrd eax,edx,16
    mov ebx,eax
    mov eax,FP_1*975/100
    sub eax,playerY
    imul ny
    shrd eax,edx,16
    add eax,ebx
    mov numerator,eax
    mov column,0
steel_leaf_column:
    mov ebx,column
    mov eax,cityRayX3D[ebx*4]
    imul nx
    shrd eax,edx,16
    mov esi,eax
    mov eax,cityRayY3D[ebx*4]
    imul ny
    shrd eax,edx,16
    add eax,esi
    mov ecx,eax
    cdq
    xor eax,edx
    sub eax,edx
    cmp eax,256
    jb steel_leaf_next_column
    mov eax,numerator
    cdq
    shld edx,eax,16
    shl eax,16
    idiv ecx
    cmp eax,4096
    jle steel_leaf_next_column
    cmp eax,zBuffer[ebx*4]
    jae steel_leaf_next_column
    cmp portalRendering3D,0
    je @F
    cmp eax,portalClipDepth3D[ebx*4]
    jb steel_leaf_next_column
@@:
    mov depth,eax
    imul cityRayX3D[ebx*4]
    shrd eax,edx,16
    add eax,playerX
    sub eax,FP_1*289/10
    imul ux
    shrd eax,edx,16
    mov esi,eax
    mov eax,depth
    imul cityRayY3D[ebx*4]
    shrd eax,edx,16
    add eax,playerY
    sub eax,FP_1*975/100
    imul uy
    shrd eax,edx,16
    add eax,esi
    test eax,eax
    js steel_leaf_next_column
    cmp eax,FP_1*3/2
    jae steel_leaf_next_column
    imul eax,256
    xor edx,edx
    mov ecx,FP_1*3/2
    div ecx
    mov sourceX,eax
    mov eax,viewEye3D
    sub eax,FP_1*19/10
    imul eax,SCREEN_H
    cdq
    idiv depth
    add eax,viewHorizon3D
    mov top,eax
    mov eax,viewEye3D
    imul eax,SCREEN_H
    cdq
    idiv depth
    add eax,viewHorizon3D
    mov bottom,eax
    sub eax,top
    jle steel_leaf_next_column
    mov ecx,eax
    mov eax,512*FP_1
    xor edx,edx
    div ecx
    mov stepY,eax
    mov eax,top
    test eax,eax
    jns @F
    xor eax,eax
@@:
    mov row,eax
    sub eax,top
    imul eax,stepY
    mov sourceY,eax
    cmp bottom,SCREEN_H
    jle @F
    mov bottom,SCREEN_H
@@:
    mov eax,row
    cmp eax,bottom
    jge steel_leaf_next_column
    imul eax,SCREEN_W
    add eax,column
    shl eax,2
    mov destination,eax
steel_leaf_pixel:
    mov edi,destination
    mov eax,depth
    cmp eax,cityDepthBuffer3D[edi]
    ja steel_leaf_next_pixel
    mov eax,sourceY
    shr eax,16
    cmp eax,512
    jae steel_leaf_next_pixel
    shl eax,8
    add eax,sourceX
    mov esi,texture
    mov eax,[esi+eax*4]
    cmp eax,80000000h
    jb steel_leaf_next_pixel
    and eax,00FFFFFFh
    mov screenBuffer[edi],eax
    mov eax,depth
    mov cityDepthBuffer3D[edi],eax
steel_leaf_next_pixel:
    mov eax,stepY
    add sourceY,eax
    add destination,SCREEN_W*4
    inc row
    mov eax,row
    cmp eax,bottom
    jb steel_leaf_pixel
steel_leaf_next_column:
    inc column
    cmp column,SCREEN_W
    jb steel_leaf_column
steel_leaf_done:
    ret
DrawBasementLeaf3D ENDP