Re: Best practices for OpenGL ES

[Sylvain <beuc@beuc.net>]

Hi,

On Mon, Jan 16, 2012 at 11:58:54PM +0100, Tobias Hansen wrote:
> Am 16.01.2012 20:01, schrieb Sylvain:
> > On Mon, Jan 16, 2012 at 02:28:19PM +0100, Tobias Hansen wrote:
> >> * Most systems with GL (and shaders) provided by Mesa also support
> GLES(2).
> >
> > Do you have examples on how this is done?
> >
> > Last time I checked, I could only find Mesa's EGL
> > src/egl/opengles2/tri demo which display a triangle through OpenGL ES
> > shaders + GLES2 EGL initialization, and I couldn't figure if:
> > - it happened to work in an OpenGL non-ES environment or,
> > - if Mesa was truly enforcing OpenGL ES mode
> 
> 
> I don't understand exactly what you want to know, but if the program is
> linked with libGLESv2 and libEGL instead of libGL and initialization is
> done using EGL, it uses GLES2. The program I mentioned earlier which
> works with GLES2 on Debian is sludge (opensludge.sourceforge.net).

My question is ultimately: can a classic desktop environment run the
GLES2-only version?
(e.g. my Athlon II desktop with its Radeon HD 5450)

This way, a simple application could be written in GLES2 and run
everywhere (desktop and mobile).


> > Also I wonder how the existing libraries/frameworks (SDL, SFML,
> > Pyglet, etc.)  behave in that regard (Do they support OpenGL ES-only
> > GPUs? Can they initialize an OpenGL ES context?).
> 
> SDL 1.2 works alongside GLES, but doesn't provide any specific support.
> Initialization has to be done using EGL. SDL 1.3 has some support for
> GLES I think.
> 
> Am 16.01.2012 23:40, schrieb Sylvain:
> > On Mon, Jan 16, 2012 at 08:29:37PM +0100, Julien Cristau wrote:
> >> On Mon, Jan 16, 2012 at 20:01:51 +0100, Sylvain wrote:
> >>
> >>> Alternatively, can the packages detect the OpenGL version at runtime
> >>> and act accordingly?
> >>>
> >> You can detect the GL version and extensions at runtime as much as you
> >> want.  GL vs GLES is not the same thing though.
> > 
> > Yeah, I meant "detect the OpenGL ES/non-ES variant at runtime and act
> > accordingly".
> 
> No, the program can't be linked against both libGLESv2 and libGL.

Too bad :/

Thanks a lot for the info.

Would there be a way to install the appropriate version automatically,
or will the user have to chose the package explicitely?

-- 
Sylvain