Hi guys,

I have some textures that when created, were created as DXT1 compressed. I'd like to map them, and get the data back out. To that end, I created a staging buffer, do a copy of the original resource to the staging buffer, then map the staging buffer. This works just fine for non-DXT compressed textures; and the data all looks correct with the test textures I used.

questions:
1. When I map a DXT1 compressed texture - am I seeing compressed bits?
2. If they are not the compressed bits, what format are they in (RGB8)?
3. If they ARE compressed bits,
3a. Can I specify the staging buffer they are mapping to have a different format such as RGB8 to get the non-compressed bits (i.e use it as a decompressor)?
3b. If I cannot do 3A, then are there software decompressors around in a library that I might use to get the raw bits back out?

Thanks in advance

1. They are compressed.
3b. You need to create additional uncompressed texture and copy DXT1 compressed one to this new one. Then you can do mapping/reading back data from uncompressed as usual. Or you can do uncompression on CPU side, for example with this: http://code.google.com/p/libsquish/

For simplicity use D3DXLoadSurfaceFromSurface() to convert a texture to a different format.

Thanks guys.

Yes, I can confirm if you just lock DXT compressed textures, the data you get back is compressed.

As for D3DXLoadSurfaceFromSurface(), you might also find (as I did) that D3DX11LoadTextureFromTexture() actually works better/easier. Yes, it is deprecated for Win8, but it was ok for our purposes. However, there is a new MS DirectXTex library for doing these operations that is compatible with Win8.

Thanks for the help!