From Jan Ciger, "I have found a problem when building OSG with Qt 5 support. Qt has the

following in the qopengl.h header:

# include <QtGui/qopengles2ext.h>
# ifndef GL_DOUBLE
#  define GL_DOUBLE GL_FLOAT
# endif
# ifndef GLdouble
typedef GLfloat GLdouble;
# endif

Unfortunately, when building for normal OpenGL (not GL/ES!) on Windows
with MSVC2012, GLdouble is not defined (it is not a macro but typedef)
and the code above produces a conflicting definition, making the
compile fail. I am attaching a bit hackish workaround for this problem
in osg/GL "

include/osg/GL

@@ -122,6 +122,12 @@
                 #include <OpenGL/gl.h>
             #else
                 #include <GL/gl.h>
+
+                // hack required to avoid conflicts with Qt
+                // Qt expects GLdouble to be a macro ?!
+                #ifndef GLdouble
+                    #define GLdouble double
+                #endif
             #endif
         #endif
     #endif