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[Public WebGL] ETC compression method.



It's great to hear that we'll have a compressed texture format available. 
The weakest link in doing web-based 3D graphics is the time the textures
take to load - so this is a critical issue.

Sadly, I have never worked with ETC images (although I know a lot about DXT).

Does anyone know of a readable online description of how ETC compresses
data?  I hate to have to figure it out from the 'etcpack' stuff.  I
presume it's a lossy scheme - and I need to understand how it loses so
that I can advise my artists on when they can usefully use compression and
when they cannot.  eg: Can I compress normal maps without getting horrible
artifacting?  Is it better to store RGB and A in separate maps rather than
trying to compress them together?  What is the trade-off between using
lower resolution uncompressed maps versus higher resolution compressed
maps?

A Google search doesn't turn up anything interesting (because 'ETC'
matches 'etcetera') and the Wikipedia article on ETC is about one line
long!  (cf gallons of available documentation on DXTn compression).

  -- Steve


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