| Re: [AD] Android & Blending Bug |
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On Wed 24 Sep 2014 07:53:58 AM Trent Gamblin wrote:
> I don't think there is a way to detect when it's needed but I'm open to
> suggestions.
>
> One possibility I thought of would be doing something like this on Android:
>
> glEnable(GL_BLEND);
> glBlendFunc(...);
> glBlendFuncSeparate(...);
>
> Perhaps stacking the calls would make things work on the problem devices
> while still allowing for separate blending on the ones that don't have
> the bug? Untested though.
Is there a great benefit to separate blendfuncs at all? If 20-25% of devices
just don't support it, it might not be worth supporting.
> Trent
>
> On 2014-09-24 1:19 AM, Evert Glebbeek wrote:
> > On 24 Sep 2014, at 5:26 , Trent Gamblin <trent@xxxxxxxxxx> wrote:
> >> I have come across an issue on Android which is very common but it's a
> >> bug with the OpenGL implementation on some devices. Many Androids don't
> >> support glBlendFuncSeparate, even though they claim to be OpenGL ES 2.0
> >> compliant -- in practice this leads to solid black pixels in place of
> >> alpha in sprites. It can't be ignored as there are a lot of very popular
> >> phones that exhibit the problem. I've heard from at least 5 people who
> >> had the problem out of maybe 20 or 25. So to fix it, I simply use the ES
> >> 1.0 path in ogl_draw.c. I don't know about anyone else but I rarely ever
> >> have used separate blending and never in a finished game. Not sure what
> >> to do though -- change Allegro or just leave it. Opinions?
> >
> > Change Allegro, since the point is for it to be useful to as many people
> > as possible, and we don't want everyone using it to have to do the same
> > work-around.
> >
> > The question is how. I don't know what platforms OpenGL ES is used one (I
> > guess Android and iOS?), but I'f force to change only on Android. If
> > possible, I'd even prefer detecting whether the work-around is necessary,
> > but I don't know how easy that would be.
> >
> > Evert
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> > rk
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Thomas Fjellstrom
tfjellstrom@xxxxxxxxxx