Add compressed textures to spec

[pjcozzi]

Did we decide if this is targeted for glTF 1.0? Since compressed textures are not part of WebGL 1.0.x, perhaps we should target this to a glTF extension, potentially after glTF 1.0.

[fabrobinet]

For sure an extension, I don't think we can promote anything to core in glTF is not not core in WebGL or OpenGL...
I believe having a proof of concept would be good rather soon than later.

[pjcozzi]

For sure an extension, I don't think we can promote anything to core in glTF is not not core in WebGL or OpenGL...

👍

[pjcozzi]

A few references:

• WEBGL_compressed_texture_s3tc
• WEBGL_compressed_texture_atc
• WEBGL_compressed_texture_pvrtc

[pjcozzi]

Is this still 1.0? It will be good to have a draft extension or two so we can flush out extensions.

[fabrobinet]

Doesn't have to be the same day, but should be come really shortly after...
Let's talk about how to proceed with glTF extensions during next call

[pjcozzi]

Another reference:

• ETC2-Package: Texture compression codecs Mandatory in OpenGL ES 3.0 and OpenGL 4.3

[pjcozzi]

@fabrobinet post 1.0?

[fabrobinet]

since we agreed on the extension syntax, this could be a glTF extension I don't think the core has to be aware of specific extension. So flagging as extension, that's something that can come after v1.0 and still be compliant with it.

[pjcozzi]

Nice comparison of compressed formats: http://joostdevblog.blogspot.nl/2015/12/texture-formats-for-2d-games-part-4.html

[pjcozzi]

Closing as duplicate with #620 and #739, which have more concrete proposals.