[osg-users] To set the glContextVersion number in the code, do I need cmake to configure the OSG_GL3_AVAILABLE option?

[OpenSceneGraph Users]

    const int width( 800 ), height( 450 );
    const std::string version( "3.0" );
    osg::ref_ptr< osg::GraphicsContext::Traits > traits = new 
osg::GraphicsContext::Traits();
    traits->x = 20; traits->y = 30;
    traits->width = width; traits->height = height;
    traits->windowDecoration = true;
    traits->doubleBuffer = true;
    traits->glContextVersion = version;
    traits->readDISPLAY();
    traits->setUndefinedScreenDetailsToDefaultScreen();
    osg::ref_ptr< osg::GraphicsContext > gc = 
osg::GraphicsContext::createGraphicsContext( traits.get() );
    if( !gc.valid() )
    {
        osg::notify( osg::FATAL ) << "Unable to create OpenGL v" << version 
<< " context." << std::endl;
        return( 1 );
    }

    osgViewer::Viewer viewer;

    // Create a Camera that uses the above OpenGL context.
    osg::Camera* cam = viewer.getCamera();
    cam->setGraphicsContext( gc.get() );
    // Must set perspective projection for fovy and aspect.
    cam->setProjectionMatrix( osg::Matrix::perspective( 30., 
(double)width/(double)height, 1., 100. ) );
    // Unlike OpenGL, OSG viewport does *not* default to window dimensions.
    cam->setViewport( new osg::Viewport( 0, 0, width, height ) );

    viewer.setSceneData( root );

    // for non GL3/GL4 and non GLES2 platforms we need enable the osg_ 
uniforms that the shaders will use,
    // you don't need thse two lines on GL3/GL4 and GLES2 specific builds 
as these will be enable by default.
    gc->getState()->setUseModelViewAndProjectionUniforms(true);
    gc->getState()->setUseVertexAttributeAliasing(true);

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