Am 05.07.2010 11:44, schrieb Mr:

> sorry to get to blender again in the discussion, I am prepared for someone to
> answer that it simply is buggy or wrong, but it behaves without any of its
> million count userbase complaining. It doesn't seem to premultiply the
> background as there is no trace of it when we use the show alpha button in the
> image window. I made a little screenshot with the process to render and see what
> I mean if you have a version of blender around:

The alpha premultiplication issue only shows very openly with 
semi-transparent stuff.

A simple test whether some piece of software does it right or not should 
be as follows:

(1) Render a scene with anti-aliasing and/or semi-transparent items and 
some pitch black object behind it filling the whole view.

(2) Remove that pitch black thing and render again with transparency 
output. View this image against a pitch black background.

If the images don't look 100% the same, /something/ is wrong. If in (2) 
semi-transparent areas appear darker and anti-aliased edges seem to 
"shrink" a little bit, chances are the software handles the PNG alpha 
channel wrong.

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