Building OSG and osgEarth in GL CORE profile

gistfile1.txt

Here are the steps for building OSG in the OpenGL CORE Profile
once you have configured CMake as usual.

1. Download the GL CORE include folder from Khronos:
   https://www.khronos.org/registry/OpenGL/api/GL/
   
2. Put it in a folder somewhere. You can put it in a folder called glcore, or
   you can make a "GL" folder in the include folder of the OSG repository and
   put it there.
   
3. In CMake, set the OPENGL_PROFILE property to GLCORE.

4. Set the GLCORE_GLCOREARB_HEADER property to the location of your
   new "GL" folder containing the CORE ARB include files. For example if your
   include file is at "C:/devel/glcore/GL/glcorearb.h", set this variable to
   C:/devel/glcore.
   
5. Set the following variables ON:
     OSG_GL3_AVAILABLE
   
6. Set the following variables OFF:
     OSG_GL1_AVAILABLE
     OSG_GL2_AVAILABLE
     OSG_GLES1_AVAILABLE
     OSG_GLES2_AVAILABLE
     OSG_GL_DISPLAYLISTS_AVAILABLE
     OSG_GL_FIXED_FUNCTION_AVAILABLE
     OSG_GL_MATRICES_AVAILABLE
     OSG_GL_VERTEX_ARRAY_FUNCS_AVAILABLE
     OSG_GL_VERTEX_FUNCS_AVAILABLE

7. Configure and build OSG.

8. If you are building osgEarth, set the same GLCORE_GLCOREARB_HEADER
   variable as you did for OSG (to the folder containing your "GL" 
   directory). Configure and build osgEarth.
   
9. Run "osgearth_version --caps" to test. You should see osgEarth report

     Core Profile = yes
     
   If you don't, try setting your envvar OSG_GL_CONTEXT_VERSION=3.3
   (or whichever version you want to use)
     
   If you want to disable the CORE profile, set the environment variable
   OSG_GL_CONTEXT_PROFILE_MASK to 2. This requests a compatibility mode
   context.
   
Enjoy!

Shortcut for new osg build:

git clone https://github.com/openscenegraph/OpenSceneGraph.git
cd OpenSceneGraph
mkdir build
cd build
cmake .. -G "Visual Studio 15 2017 Win64"
-DCMAKE_BUILD_TYPE=Release
-DWIN32_USE_MP=ON
-DOSG_GL3_AVAILABLE=ON
-DOPENGL_PROFILE="GLCORE"
-DGLCORE_ROOT=c:\path_to\glarb\

Setting profile to GLCORE will execute the cmake setup for GL3 which includes turning off all the variables in #6. I submitted a PR to fix the context version because right now it still needs to be set to 3.3 but cmake should set it to 3.3 when OSG_GL3_AVAILABLE is set to ON.

And for vcpkg builds, also include -DCMAKE_TOOLCHAIN_FILE=[vcpkg root]\scripts\buildsystems\vcpkg.cmake