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Re: [Public WebGL] extension proposal: WEBGL_compressed_texture_pvrtc









On Tue, Aug 7, 2012 at 2:42 PM, Benoit Jacob <bjacob@mozilla.com> wrote:
Hi,

This is about a new extension proposal, WEBGL_compressed_texture_pvrtc.

The pull request is there:
https://github.com/KhronosGroup/WebGL/pull/11

I've attached the generated HTML. Unfortunately Github doesn't appear to allow viewing HTML files directly off the repository.

Github requires pushing to a branch named "gh-pages" to serve live content. Currently though it seemed better to serve the live stuff from khronos.org

Great! Out of curiosity, could you explain how this works? Are all commits in KhronosGroup/WebGL automatically reflected on this site?

Thanks for merging the pull request, as well.

Now please discuss promotion to draft status!

Benoit

 

The need for mobile compressed texture formats is real. This is the #1 thing we're being asked for my game developers regarding Web games on mobile devices.

Also, while I understand that ETC2 is coming, we need something that will help WebGL take off on today's mobile devices.

This extension stays close to the corresponding OpenGL ES extension,
http://www.khronos.org/registry/gles/extensions/IMG/IMG_texture_compression_pvrtc.txt

In particular, the power-of-two and texSubImage-must-replace-the-whole-image requirements come from there.

You might notice that the formulas for butter byte length are looking different: for the 2bpp formats, the OpenGL ES extension has

  ( max(width, 16) * max(height, 8) * 2 + 7) / 8

whereas the WebGL extension proposal has

  max(width, 16) * max(height, 8) / 4

The two formulas are in fact equivalent, given that width and height must be powers of two. The latter formula is just a simplification taking advantage of this fact.

Please, consider it for promotion to draft status so that implementation can start.
Benoit