DXT compressed textures

I stumbled across this one recently apparently nVidia and ATI have ways that the texture files can be compressed off line then rendered by the video card basically it uses less video memory to achieve the same results and requires less data to be sent to the video card.

Anyone know much about it?

Thanks John

The only thing I know about it is I have to remove the line that references it in the texture.txt file to get the texture to show up on my Nvidia 7600GS card running TRS2004 in OpenGL.

Maybe it is Directx only.

William

Hi John,
Martin Wright who has created a heap of little Graphics programs for free for the Microsoft Flightsims and Trainsim has a nifty program called DXT Bitmap.You can convert Bitmaps etc backwards and forwards and You can retain your Alpha channels etc when reskinning aircraft etc.Follow the link below.

http://www.mnwright.btinternet.co.uk/

God Bless
Frank

Franglen said:

Hi John,
Martin Wright who has created a heap of little Graphics programs for free for the Microsoft Flightsims and Trainsim has a nifty program called DXT Bitmap.You can convert Bitmaps etc backwards and forwards and You can retain your Alpha channels etc when reskinning aircraft etc.Follow the link below.

http://www.mnwright.btinternet.co.uk/

God Bless
Frank

Click to expand...

There are five different variations of DXT compression

http://en.wikipedia.org/wiki/S3TC

MSTS only used DXT1 which had some limitations and that is the version that Martin offers. However DXT 5 looks as if it offers good compression without the earlier implementation issues of DXT1 or DXT1A and is directly supported by the latest graphics cards.

I also suspect one reason for the latest graphics cards only supporting 512 Mb of memory are with DXT5 this would give the equivalent of 2 Gigs of memory on the card.

My personal feeling is either Trainz adopts DXT5 or sinks as the competing SIMS will have much better graphics on the same hardware.

There appears to be at least one transport SIM that has it and promotes it as a sales point.

Cheerio John

DXT (DirectX Textures) may be DirectX only - I don't know if OpenGL supports that format. Otherwise, I would agree - these uncompressed TGA files are killing us

Would DXT5 compression work with DirectX9?

Pencil42 said:

DXT (DirectX Textures) may be DirectX only - I don't know if OpenGL supports that format. Otherwise, I would agree - these uncompressed TGA files are killing us

Click to expand...

They are also known as S3 Texture Compression and are not specifically DirectX. From what I can see so far if the graphics card supports them they can be used in place of a .TGA or .BMP file.

Trainz would have to accept them but I think that's all. It would mean some of the older graphics cards wouldn't be able to run them and it might be easier to say in marketing terms DirectX 10 must be supported but I'm under the impression that nVidia support them under a propitiatory OpenGL extension.

A second SIM / game is apparently using them.

http://en.wikipedia.org/wiki/Unreal_Tournament

nVidia is offering support specifically on the 8800 GTX

http://developer.nvidia.com/object/texture_tools.html

ATI

http://ati.amd.com/developer/tools.html

So it looks like it might be something to look out for on any new graphics cards.

Cheerio John