Thread: Read Graphic Card Output

I hope im in the right section so if not please can a mod move this

So now to my "prob."

I was playing CoD and again was frustrated about all the cheater ingame. So i thought about "how would i prevent ppl from cheating in my game" and came up with the idea to check the useres screen at a specific point. If e.g. a wallhack is applyed the shown image should differ from the original. anyway i dont wanna discuss anti-cheat techniques but want to know, how (can i at all?) directly access the graphic card output with c++ under MS windows?

since im a newby at graphic programming (had some tries with OpenGL) i guess you have to read some sort of buffer that is send to the monitor via the port (dvi, vga, what ever).
I hope any1 of you can enlight me here a bit (or more )

thanks in advance

ghost

Believe me, it would be a LOT easier to find a game that's not overrun by lamearsed wimps who's only way to get along in life is to cheat (lie, steal, etc.)

the game (or others) are not the reason but the trigger for my research. im just curious "how to"

If it's on a different computer there's not much chance of doing it in any effective way... It would require planting code in the other machine to send the information to you... At best you might get a screen snapshot (a still picture) but the code to do this would be extremely invasive of the other system and would certainly qualify as a virus.

Bear in mind that direct access to the hardware framebuffer is restricted. You can copy back into system memory to do your comparison but this will affect the FPS. If your game is a strategy game then you might be able to get away with it.

thank you all for your responds. as i said im not about to build a anti-cheat engine and i dont want to code some sort of virus or trojan. ill check forum and inet for this screenshot code and for more tuts on framebuffer reading.

ot. the idea to use this as an anti-cheat was to build a hash of the image and compare it with the original .. on a Full HD resolution thats about 6mb to transform into a hash value which shouldnt kill a standart system.

There are ways to gain access to the framebuffer via Direct3D and OGL. It is also possible to gain access to this buffer from another process but it is not something we normally discuss in this forum. Screenshots are fairly harmless but if you force another computer to take screenshots keep in mind you will probably cause more problems in the game due to lag than solving any cheating issues. My recommendation is let PunkBuster or the mods handle the cheaters and/or move on to a game with less cheating.

learn about the possebilities.

Unfortunately what you are talking about is usually something we do not discuss on the forums because it involves poking around in the address space of another process. It is possible to execute your code in the address space of another process but you can google that and find a million sites willing to tell you how to do it. If this is an OpenGL app you will need to execute the call to grab the frame buffer in the address space of the game. For Direct3D you will need to execute IDirect3DDevce9::GetBackBuffer() (for DirectX 9.0c) or the equivalent in DirectX 10 (depending on the version the game uses). Once you grab that then you can write the data to a file using D3DXSaveTextureToFile().

When you have your own Direct3D device this is a very simple process but the hurdle you must overcome is you are trying to get the game to execute your code on a keypress or on a timer event.