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Re: [Public WebGL] Weird alpha issue.



----- Original Message -----
> On 10/31/2010 10:26 AM, Benoit Jacob wrote:
> > ----- Original Message -----
> >
> >> Todays' version:
> >>
> >> Build identifier: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b8pre)
> >> Gecko/20101031 Firefox/4.0b8pre
> >>
> >> ...didn't fix anything.
> >>
> > Yes, in my last email I said tomorrow's version.
> >
> Ah! I assumed you'd sent the email last night. Sorry.
> > Are you doing any pixelStore() calls? Are you setting the
> > PREMULTIPLY_ALPHA parameter there?
> >
> I do this in the "onload" function - but that's the only pixelStore
> call:
> 
> image.onload = function ()
> {
> gl.bindTexture ( gl.TEXTURE_2D, texture ) ;
> gl.pixelStorei ( gl.UNPACK_FLIP_Y_WEBGL, true ) ;
> gl.texImage2D ( gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA,
> gl.UNSIGNED_BYTE, image ) ;
> gl.generateMipmap ( gl.TEXTURE_2D ) ;
> gl.bindTexture ( gl.TEXTURE_2D, null ) ;
> pendingTextures -- ;
> } ;

OK, no alpha premultiplication there. So no premultiplication should happen. If you can run Minefield in a profiler showing the list of all functions that are called, you should then NOT see any symbols of the form  ...packRGBA8To...Premultiply...  (where the ellipsis ... match any string). If you see any such Premultiply symbols, that means that we call the wrong texel packing function, wrongly premultiplying, causing transparent textures to be darker than they should.

Benoit
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