Re: [Public WebGL] Premultiplied alpha blending and issues with color accuracy

[Thor Harald Johansen <thj@thj.no>]

On 5/11/2012 10:46 AM, Florian Bösch wrote:
> On Fri, May 11, 2012 at 10:39 AM, Thor Harald Johansen <thj@thj.no
> <mailto:thj@thj.no>> wrote:
>
>     Simultaneously? In a single shader? AFAIK, WebGL only allows one active
>     texture per drawing operation.
>
> You can only write to one texture at a time. You can read from many
> textures. If you look at http://webglstats.com/ you can see that most
> desktops (99.9%) can read from 16 textures, and most mobiles (100%) can
> read from 8.

Thanks for that link. Didn't know about that website!

And okay, from your and Ben's comments, it seems I'm going to have to 
look more carefully at how multi-texturing actually works. All the 
examples I found were doing things like switching textures for each side 
of a cube, etc. None demonstrated blending of multiple textures. I find 
API references to be really hard to learn from. :/

So okay, texture ping-pong and multi-texturing are both promising 
avenues. I might write a shader that takes 8 texture units and blends 
them together to the main frame buffer, and enforce a limit of 8 layers 
in the user interface. From practical experience, people rarely use more 
than perhaps 5 layers anyway.

Thor

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