Right now I have:
gl.glEnable(gl.GL_BLEND)
gl.glBlendFunc(gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA)
Which I believe makes sense for what I want, however I believe either
the values I'm using for alpha don't make sense, or a problem is being
caused by having a black background behind what I have there, does
that make sense?
On Dec 14, 5:44 pm, "Alex Holkner" <[email protected]> wrote:
> On Mon, Dec 15, 2008 at 10:20 AM, Alex_Gaynor <[email protected]> wrote:
>
> > Ah thanks, that makes sense, although it would be nice if it were
> > documented(I suppose this is considered obvious to people who actually
> > work with OpenGL :) ). I think the most sensible place to call this
> > would be in my Polygon.draw method.
>
> > I have an additional question about how exactly the alpha channel
> > works. Right now I have the color mode set to "c4B", which I think
> > means I provide 4 values(Red, green, blue, alpha), I'm trying to do
> > generate something similar to the partially transparent A over B as
> > seen
> > here:http://upload.wikimedia.org/wikipedia/commons/2/2a/Alpha_compositing.svg
> > . With the end result being something like what's seen at
> >http://alteredqualia.com/visualization/evolve/. a) Is my
> > understanding of c4B correct, and what value for the alpha compoment
> > makes sense?
>
> Yes, however you also need to explicitly enable blending:
>
> glEnable(GL_BLEND)
>
> You can change the blend function from the default (SRC_OVER) with
> glBlendFunc. Not all of the blend functions in that wikipedia image
> are supported by OpenGL.
>
> Alex
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