[osg-users] ProgramBinary and shader composition - does it work?

[OpenSceneGraph Users]

Hi Glenn,

The way I'd tackle the issue of compilation of shaders taking a long time
is to avoid doing it frame time, doing as much work in scene graph
setup/compilation.

For you usage case I assume you have a complex shader with many different
constant inputs either controlling code paths or values, and the scene
graph is configuring these as the values change provided by the scene graph
via the #PCS defines.  If you can work out what range of different defines
you will need then build a subgraph with each of these combinations and the
sharing osg::Program that depends upon these then compile this subgraph,
once it's all compiled you can discard it save for the osg::Program that
you then reuse in your main application.

This approach should in theory populate the osg::Program with all the GLSL
program combinations that you will need and the OSG can internally just use
these when rendering your main scene graph.

Robert.

On Sun, 23 Feb 2020 at 14:14, OpenSceneGraph Users <
osg-users at lists.openscenegraph.org> wrote:

> Robert,
>
> I have an application with several complex shaders. According to the
> profiler some of them take a while to link (glLinkProgram), long enough to
> cause a frame drop. This app cannot tolerate any frame drops so I was
> looking into glProgramBinary as a possible mitigation. I'm open to other
> ideas of course.
>
> Glenn Waldron / osgEarth
>
>
> On Thu, Feb 20, 2020 at 10:31 AM OpenSceneGraph Users <
> osg-users at lists.openscenegraph.org> wrote:
>
>> Hi Glenn,
>>
>> On Wed, 19 Feb 2020 at 17:56, OpenSceneGraph Users <
>> osg-users at lists.openscenegraph.org> wrote:
>>
>>> I was looking in the glProgramBinary support in osg::Program. I don't
>>> *think* it is integrated with your "pragmatic" define-based shader
>>> composition system. Specifically there doesn't seem to be a way to
>>> associate a ProgramBinary with a particular defineString at the
>>> PerContextProgram level.
>>>
>>> Am I right? And if so will you consider a submission to make this work?
>>>
>>
>> When writing the #pragma(tic) shader composition functionality I was just
>> focused on conventional GLSL compiled shaders, I didn't consider
>> glProgramBinary, so no idea of how it might interact, I don't expect it
>> would would work though as the main task of shader composition is
>> compositing the shaders to compile and compiling these at runtime.
>>
>> Is there a reason why you are trying to the the glProgramBinary path?
>>
>> Robert.
>>
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>>
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