[Development] Changing GLdouble typedef in src/opengl/qgl.h

[Saikrishna Arcot]

I should have mentioned that these libraries are using Qt 4, and it would be non-trivial to change them to Qt 5 just for compilation purposes.

I wasn't aware that doubles weren't supported on GLES. Based on that, and rereading the forum post here (http://forum.openscenegraph.org/viewtopic.php?t=11504[1]), it seems like there are two standards:

1. Accept doubles, use double for internal processing (if any), and cast it to float when calling the appropriate GLES function.
2. Accept and use only floats for both internal processing and calling GLES functions.

I wonder which one might be better to follow.

On Wednesday, September 03, 2014 05:26:23 Gunnar Sletta wrote:
> 
> On 03 Sep 2014, at 01:18, Saikrishna Arcot <saiarcot895 at gmail.com> wrote:
> 
> > Hi,
> > 
> > I was looking at trying to get some libraries and applications to compile in Ubuntu for armhf (which supports only OpenGL ES for performance reasons). When I was trying to get OpenSceneGraph to compile, I noticed that in Qt's src/opengl/qgl.h, GLdouble is aliased to GLfloat. OpenSceneGraph (and some other applications) expect GLdouble and GLfloat to be different things, and some applications typedef GLdouble to double in their own code.
> > 
> > Is there a reason why GLdouble is typedefed to GLfloat? If this was changed to typedef to double instead, is there a risk of breaking something within Qt?
> 
> There is nothing in stock ES that supports double precision floats without the use of extensions, so I suspect it was done to make the initial port easier...
> 
> Anyway, you should use Qt 5 and QOpenGLContext (not QGLWidget / QGLContext) which doesn't have this define and which should be easier to integrate with OpenSceneGraph as you are better control of the GL context.
> 
> cheers,
> Gunnar
> 
> > 
> 

-- 
Saikrishna Arcot

--------
[1] http://forum.openscenegraph.org/viewtopic.php?t=11504
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