[GEM-dev] gem cvs alpha-depth bug?

[guenter geiger]

On Fri, 28 Nov 2003, chris clepper wrote:
> At 7:23 PM +0100 11/28/03, guenter geiger wrote:
> >Ooops, obviously my fault.
> >I have changed default behaviour of alpha to the one it was in 0.87.
> >Damn, I really forgot about that, ...
> >
> >It is not really a bug, but a feature that lets you use alpha blending
> >independent from position, but the default behaviour should of course
> >stay the same. Sorry ..
>
> The alpha object is really a mess though.  The depth test message is
> 'auto' ??  That's not very descriptive, and neither is 'test' or
> 'function'.  How does the following strike you?
>
> - 'alpha-test' for setting m_alphaTest (I'm not even sure what this
> really does...)
> - 'depth-test' or just 'depth' for turning the depth mask on and off
> - 'source' (or 'src') for setting the source arg for glBlendFunc
> - 'destination' (or 'dst') for setting that arg of glBlendFunc
>
> The src/dst messages could either take numbers for each of the
> possible gl constants or a string comparison could be done on the
> full name.  This would allow for any combination, although I have to
> admit only a few are even very useful.
>
> Also, the depth object works opposite of the way one would expect.
> Sending a 1 to it turns off the depth buffer??  That doesn't make a
> whole lot of sense to me.
>
> I'm going to write a tutorial on render order and how it affects
> things like blending, because, to be perfectly honest, I had to look
> at Ben's patch twice before I realized why I couldn't get the damned
> red square to be inside the cube!!  Obviously, one has to consider
> the render order in this case to determine which pixels are already
> in place for the alpha blending function to work on.  I think Ben or
> someone had asked about Z-buffer sorting that would basically change
> this dynamically, but I'm not sure how we would do this in GEM
> without some sort of mad caching scheme.

Me neither..

The naming is really a problem though :(

Guenter


>
> cgc
>
> >Guenter
> >
> >>
> >>  I'm using lighting (because lighting tends to get messed up when using
> >>  "depth" to show the effect. without a depth object in a chain, the cube
> >>  looks identical to its depth counterpart, as long as the alpha object is
> >>  in the chain. If I turn off the alpha object it works fine. (looks as it
> >>  does without using depth.
> >>
> >>  Here is an example patch.
> >>
> >>  Ben
> >>
> >>
> >
> >
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