Re: [Openexr-devel] OpenEXR 1.5.0, OpenEXR-Images 1.5.0 released

[Florian Kainz]

Simon Green wrote:
> Hi Florian,
>
> Thanks for the description, this is a pretty clever encoding. Now that I've 
> looked at it, it's actually more like shared-exponent encoding of pixel deltas 
> than DXT. It seems like it should be feasible to do decoding on the GPU, 
> especially given the integer instructions available in new DX10-class hardware. 
> You would probably have to download the compressed 14-bit values as a 16-bit 
> texture, which is a bit of a waste.

Fitting GPU-based decompression into the IlmImf library is
certainly an interesting challenge.  I haven't thought about
how one might do that.

> I'm not sure if you're aware of this, but DX10 also includes includes two new 
> compressed HDR texture formats - a shared exponent format like RGBE but with 9 
> bit mantissas (9/9/9/e5), and also a a packed float format (6e5/6e5/5e5). Would 
> it be useful to add support for these formats to OpenEXR?
>
> http://developer.download.nvidia.com/opengl/specs/GL_EXT_packed_float.txt
> http://developer.download.nvidia.com/opengl/specs/GL_EXT_texture_shared_exponent.txt

Whether some form of direct support for compressed hardware
texture formats is useful depends on what you want to achieve.
If you are looking for something that can be uploaded to the
graphics card as fast as possible, for example, in a game,
file formats optimized for this one purpose, such as DDS,
would be hard to beat.