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scarypajamas

hall of mirrors effect?

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In quake 3, when I type "noclip" into the console and walkout side the game map, I get a hall of mirrors effect. Why is this? I read somewhere it was because the game is only clearing the depth buffer and not the color buffer. Is this true, and if so does it speed up performance to do so?

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Heya,

That's correct it isnt clearing the color buffer.

I'm not sure if it's still a worthwhile optomization but yeah, the idea is you save having to fill the screen with black before you render anything else, which can take some time.

If you know you are going to be rendering over every pixel anyways, why clear it? (:

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Some old hardware is very, very slow at clearing the buffer, but I would think anything in the DX9 era or newer wouldn't have that problem any more.

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According to Nvidia, atleast for SLI, "Clearing the color and z information of a render target prior to its use indicates to the driver and the GPU that any existing data in the render target is irrelevant. Conversely, not clearing that data indicates that the data may be relevant and thus needs to be maintained, and in the case of SLI configurations shared between GPUs."[1]

This guide is a good read for optimization tips, so I highly recommend it. ;)

[1]http://developer.download.nvidia.com/GPU_Programming_Guide/GPU_Programming_Guide.pdf

[Edited by - n00body on July 21, 2009 10:23:49 AM]

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