Re: [osl-dev] Explain the logic with Cmake searching for OpenGL

[Larry Gritz]

This is OSL you're talking about?

Hmmm... OpenGL is not needed for OSL.  I see that externalpackages.cmake does some searching for OpenGL and GLEW.  I suspect this is left over from eons ago when we copied the CMake files over from OIIO, which does (optionally) use OpenGL.  They are unneeded, I will remove those searches.  See this pull request that I just submitted:  https://github.com/imageworks/OpenShadingLanguage/pull/163

I've already committed this to the master branch, but am happy to back-port it to the 1.2 branch if that's helpful to you.

But in the mean time, this should not stand in your way.  Other than the strange "OPENGL_FOUND=...", there is no consequence to not finding OpenGL at build time, since it's not used anyway.

Now then, just in case you have the same concern about OIIO -- it does search for OpenGL and it does use it, but only for the viewer "iv."  The build proceeds just fine even if OpenGL is not found, but it only builds the various libraries and not the "iv" viewer.  Some people don't want/need that anyway, so we let the build proceed. Lack of OpenGL does not affect the core libOpenImageIO, nor operation of any of the image format readers/writers.  But, if you want to build OIIO and need "iv" working and the CMake scripts are not properly finding OpenGL on your system, please do let us know (on oiio-dev) and we'll work with you to find a modification to the script that will find OpenGL on a wider range of platforms. 

-- lg

On Oct 4, 2012, at 10:10 PM, Marc Driftmeyer wrote:

From the external packages cmake script:

# OpenGL setup

if (USE_OPENGL)
    find_package (OpenGL)
endif ()
message (STATUS "OPENGL_FOUND=${OPENGL_FOUND} USE_OPENGL=${USE_OPENGL}")

# end OpenGL setup


Platform Testing: Debian Linux

GPGPU: Nvidia and AMD

Situation: Linux nomenclature for OpenGL is GL, not OpenGL so finding OpenGL is going to produce exactly what I expect: NOT FOUND.

Output in config:

-- Boost found TRUE
-- Boost include dirs /usr/include
-- Boost library dirs /usr/lib
-- Boost libraries    /usr/lib/libboost_filesystem-mt.so;/usr/lib/libboost_regex-mt.so;/usr/lib/libboost_system-mt.so;/usr/lib/libboost_thread-mt.so;pthread
-- OPENGL_FOUND= USE_OPENGL=
-- TBB_HOME = unknown
-- TBB includes = /usr/include
-- TBB library =
-- LLVM version  = 3.2svn
-- LLVM dir      = /usr/local
-- LLVM includes = /usr/local/include
-- LLVM library  = /usr/local/lib/libLLVMCore.so
-- LLVM lib dir  = /usr/local/lib
-- LLVM OSL_LLVM_VERSION = 32svn
-- LLVM library  = /usr/local/lib/libLLVMCore.so
-- CMAKE_INSTALL_RPATH = /usr/local/lib


Question: Is this a deliberate oversight?

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Larry Gritz
l...@larrygritz.com