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mrmrcoleman

DXT Textures...

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Hello, with DXT textures, what kind of compression ratio is realistic. I am trying to decide how to create the level backgrounds for my new 2d game and one solution is to have 2 5096x5096 textures at 32 bits each used to represent all the data that would be needed for the game interaction. Uncompressed this is 2 x 4 x 5096 x 5096 bytes = 207753728 bytes. or approximately 200 megabytes... This would need to be roughly halved to be even remotely possible. Thanks, Mark.

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4096x4096 is the max texture size supported by any hardware.

With 2 of them uncompressed that's 128MB. DXT would take it down to 32MB.

However, a lot of cards only support 2048x2048 textures or some even smaller.

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Quote:
Original post by mrmrcoleman
Wow, thats a quarter. Is that the 'on card' size or just on disk?

Mark


1) DXT compression is "lossy" rather than lossless (i.e. the quality isn't as good as the original uncompressed image, like JPEG) so you shouldn't compare the compression ratios to lossless formats like PNG. Understanding the different DXT formats available will help you choose which is best for your images. Take a look at the "Getting Started->Direct3D Textures->Compressed Texture Resources" section of the Direct3D docs for more information.


2) Whether or not that's the 'on card' memory saving depends on whether the card supports DXT compressed textures in hardware.

If your card does support DXT compressed textures, then yes, that's the 'on card' size.

If your card doesn't support DXT compressed textures, then they'll be decompressed into a normal format on the card so the saving will only be on disk.

IIRC the first cards to support DXT compression were the S3 Savage range back in around 1998-1999 (Microsoft licensed/bought DXTC from S3, it was originally known as S3TC). Most cards released since around 2000-2001 support DXTC in hardware.

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