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low_res_textures.md

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Low Resolution Textures

On modern machines all textures in the game appear at a much lower resolution then originally intended. This is due to an overflow in the integer used to store how much VRAM is avaliable on the client. The game detects a high amount of VRAM as too little VRAM due to the overflow and forces low resolution textures.

Procedure

The following lines of assembly are from the procedure from .text:00642D80 to .text:006433FE. The procedure is compiled from PCMain.cpp and is responsible for loading the registry configuration.

.text:0064302E	mov     ecx, offset window
.text:00643033	call    GetTextureAvaliable
.text:00643038	cmp     eax, 13000000
.text:0064303D	jge     short loc_643045
.text:0064303F	mov     g_UseLowResTexture, edi
.text:00643045
.text:00643045 loc_643045:

This can be translated to the following C style code:

if ( GetTextureAvaliable() < 13000000 )
    g_UseLowResTexture = true;

This is the equivalent of checking for under 13MB of VRAM. However the return value of GetTextureAvaliable() is a signed integer, if you exceed 2147483647 bytes or 2GB the integer will overflow and the statement will become positive setting the UseLowResTexture global to true.

Patch

We can simply remove the instructions as the default value for the global value UseLowResTexture is 0 and most modern systems using this patch will not want the low resolution textures.

Simply NOP out the following addresses: .text:0064302E to .text:00643045.

This fixes the issue with clients with over 2GB of VRAM having low resolution textures.