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Re: [Public WebGL] ETC texture compression.



On Aug 26, 2010, at 5:25 PM, Steve Baker wrote:

> Chris Marrin wrote:
>> Assuming the copyright issues for ETC1 get sorted out I think we
>> should just make it a part of the spec rather than an extension. The
>> availability of a software decoder would allow it to be implemented on
>> platforms without ETC1.
> The problem with resorting to software decoders is that most (if not
> all) desktop systems don't provide support for ETC1.  You'd package your
> textures into ETC1, suffer the horrific loss of image quality...and then
> discover that you're actually not saving any video memory or improving
> texture cache coherency at all!   ETC1 does help your network bandwidth
> (the files are 6:1 compressed) - but the average file compression rate I
> get from PNG's zlib compression is 3.6:1 (averaged over all the maps in
> my game) - so the network bandwidth savings from ETC are less than a
> factor of two over PNG.  Given that, I can't imagine many people
> preferring ETC1 over PNG for desktop systems.

How does it compare to jpeg?  Given the current  texture loading model is to load from Image (or Canvas) objects you need to transmit your data to the UA in a form the UA understands.

In all honesty I find myself wondering if the API should simply be something akin to telling the WebGL implementation to use a compressed texture if possible, then leaving it up to the implementation to determine the best format on the current platform.

--Oliver


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