; Static world-space lightmap: built once, sampled without walking the light list.
.code
AddCityLight3D PROC uses ebx esi edi x:DWORD,y:DWORD,rx:DWORD,ry:DWORD,power:DWORD
    local gx:DWORD,gy:DWORD,minX:DWORD,maxX:DWORD,maxY:DWORD,dy2:DWORD
    mov eax, x
    sub eax, rx
    jns @F
    xor eax, eax
@@:
    mov minX, eax
    mov eax, x
    add eax, rx
    cmp eax, CITY_LIGHT_W-1
    jle @F
    mov eax, CITY_LIGHT_W-1
@@:
    mov maxX, eax
    mov eax, y
    sub eax, ry
    jns @F
    xor eax, eax
@@:
    mov gy, eax
    mov eax, y
    add eax, ry
    cmp eax, CITY_LIGHT_H-1
    jle @F
    mov eax, CITY_LIGHT_H-1
@@:
    mov maxY, eax
city_light_row:
    mov eax, gy
    sub eax, y
    imul eax, 256
    cdq
    idiv ry
    imul eax, eax
    mov dy2, eax
    mov eax, minX
    mov gx, eax
city_light_cell:
    mov eax, gx
    sub eax, x
    imul eax, 256
    cdq
    idiv rx
    imul eax, eax
    add eax, dy2
    cmp eax, 65536
    jae city_light_next
    neg eax
    add eax, 65536
    mov ecx, eax
    mul ecx
    shrd eax, edx, 16
    imul eax, power
    shr eax, 16
    mov ebx, gy
    shl ebx, 9
    add ebx, gx
    add eax, cityLightMap3D[ebx*4]
    cmp eax, 320
    jbe @F
    mov eax, 320
@@:
    mov cityLightMap3D[ebx*4], eax
city_light_next:
    inc gx
    mov eax, gx
    cmp eax, maxX
    jle city_light_cell
    inc gy
    mov eax, gy
    cmp eax, maxY
    jle city_light_row
    ret
AddCityLight3D ENDP

BuildCityLighting3D PROC uses ebx esi edi
    lea edi, cityLightMap3D
    xor eax, eax
    mov ecx, CITY_LIGHT_W*CITY_LIGHT_H
    rep stosd
    lea esi, cityObjects3D
    mov ebx, CITY_PROP_COUNT
city_light_lamp:
    cmp [esi].CityProp3D.asset, OFFSET cityPropsPack3D
    jne city_light_lamp_next
    cmp [esi].CityProp3D.frame, 3
    jne city_light_lamp_next
    mov eax, [esi].CityProp3D.posX
    sar eax, 13
    mov edx, [esi].CityProp3D.posY
    sar edx, 13
    invoke AddCityLight3D, eax, edx, 25, 25, 240
city_light_lamp_next:
    add esi, SIZEOF CityProp3D
    dec ebx
    jnz city_light_lamp
    ; Only genuinely lit windows/storefronts cast a narrower spill across the curb.
    mov esi, 3
city_light_windows:
    movzx eax, cityMap3D[11*32+esi]
    cmp eax, 65
    je city_light_near_window
    cmp eax, 62
    jne city_light_far_window
city_light_near_window:
    lea eax, [esi*8+4]
    invoke AddCityLight3D, eax, 12*8+2, 7, 16, 96
city_light_far_window:
    movzx eax, cityMap3D[17*32+esi]
    cmp eax, 65
    jne city_light_next_window
    lea eax, [esi*8+4]
    invoke AddCityLight3D, eax, 17*8-2, 7, 16, 96
city_light_next_window:
    inc esi
    cmp esi, 29
    jb city_light_windows
    ; The casino door is at y=8; this does not illuminate an imaginary closed facade.
    invoke AddCityLight3D, 22*8+4, 8*8+2, 14, 22, 150
    mov cityLightReady3D, 1
    ret
BuildCityLighting3D ENDP

SampleCityLight3D PROC x:DWORD,y:DWORD
    xor eax, eax
    cmp cityLighting3D, 0
    je city_light_sample_done
    cmp cityLightReady3D, 0
    je city_light_sample_done
    mov ecx, x
    sar ecx, 13
    cmp ecx, CITY_LIGHT_W
    jae city_light_sample_zero
    mov edx, y
    sar edx, 13
    cmp edx, CITY_LIGHT_H
    jae city_light_sample_zero
    shl edx, 9
    add edx, ecx
    mov eax, cityLightMap3D[edx*4]
    ret
city_light_sample_zero:
    xor eax, eax
city_light_sample_done:
    ret
SampleCityLight3D ENDP

ShadeCityGround3D PROC uses ebx esi edi rgb:DWORD,x:DWORD,y:DWORD,ambient:DWORD
    invoke SampleCityLight3D, x, y
    mov esi, eax
    ; Tint the material itself, retaining paving detail instead of painting a flat glow.
    mov eax, rgb
    shr eax, 16
    and eax, 255
    mov ecx, ambient
    add ecx, esi
    imul eax, ecx
    shr eax, 8
    cmp eax, 255
    jbe @F
    mov eax, 255
@@:
    shl eax, 16
    mov edi, eax
    mov eax, rgb
    shr eax, 8
    and eax, 255
    mov ecx, esi
    imul ecx, 3
    shr ecx, 2
    add ecx, ambient
    imul eax, ecx
    shr eax, 8
    cmp eax, 255
    jbe @F
    mov eax, 255
@@:
    shl eax, 8
    or edi, eax
    mov eax, rgb
    and eax, 255
    mov ecx, esi
    shr ecx, 2
    add ecx, ambient
    imul eax, ecx
    shr eax, 8
    cmp eax, 255
    jbe @F
    mov eax, 255
@@:
    or eax, edi
    ret
ShadeCityGround3D ENDP

; Bright warm panes and lantern glass emit light; dark windows/brick do not.
IsCityEmissive3D PROC uses ebx rgb:DWORD,material:DWORD
    cmp cityLighting3D, 0
    je city_not_emissive
    mov eax, material
    cmp eax, 58
    je city_emissive_color
    cmp eax, 62
    je city_emissive_color
    cmp eax, 65
    je city_emissive_color
    cmp eax, 70
    jne city_not_emissive
city_emissive_color:
    mov eax, rgb
    shr eax, 16
    and eax, 255
    cmp eax, 180
    jb city_not_emissive
    mov edx, rgb
    shr edx, 8
    and edx, 255
    cmp edx, 96
    jb city_not_emissive
    sub eax, edx
    cmp eax, 32
    jl city_not_emissive
    mov ebx, rgb
    and ebx, 255
    sub edx, ebx
    cmp edx, 24
    jl city_not_emissive
    mov eax, 1
    ret
city_not_emissive:
    xor eax, eax
    ret
IsCityEmissive3D ENDP