OpenGL Libraries

Question

Have the OpenGL libraries installed, glut.h, gl.h using visual studio and the called routines glClear(...), glColor(...), glRotate(...), etc. are global calls unresolved when I execute the "build" command. Have had a lot of problems getting the correct libraries for OpenGL loaded into visual studio, C++ and not sure what is happening. Such a simple task should not be so difficult. When I use OpenGL in Fortran and Basic programs is very simple! Using in Visual Studio almost impossible. Have had several comments from this site about getting the libraries, how to "include", etc. so far, have not worked. Even though the #include commands do not give an error, the OpenGL statements still unresolved. Seems obvious that a library element is not being included, any ideas will help. Sid Kraft

Answer 1

*.h files are not libraries, they are header files that define definitions to access the library. You must still add the libraries to project build. For c++ you add the library path as a library search path, add a reference to the library name and add include search path. As you are using vs studio in the project properties:

• C/C++ > General > Additional Include Directories and add your path to the gl include files
• Linker > General > Additional Library Directories and add your path to gl library files
• Linker > Input > Additional Dependencies and append the library file names.

I assume your missing step three or you would get not found errors for the libraries. I don’t know which GL package of libraries you picked., so can not give the library names. Give us which gl library you picked and we can give more help.

Note: glut.h is obsolete, you should be using a more modern gl library.

Answer 2

Hello @Sid Kraft ,

It looks like the headers are being found correctly, but the linker still does not have access to the OpenGL import library.

For the functions you mentioned, Microsoft's documentation for glClear and glRotatef indicates n Gl.h and require linking against Opengl32.lib.

In Visual Studio, make sure Opengl32.lib is added under Linker > Input > Additional Dependencies as described in the Linker Property Pages documentation.

If the linker still cannot locate Opengl32.lib, also verify the paths configured under Linker > General > Additional Library Directories as documented here. In most cases, however, Opengl32.lib is provided by the Windows SDK and should be found automatically.

In short, #include <gl/gl.h> only provides the OpenGL function declarations. You must also link Opengl32.lib so the linker can resolve the corresponding OpenGL entry points.

If the issue persists after adding the library, please share a full LNK20xx error message from the build output. That will help identify exactly which symbol is unresolved and whether an additional library is required.

I hope this helps. If you found my response helpful or informative, I would greatly appreciate it if you could follow this guidance or provide feedback.      

Thank you.     

 

Answer 3

Are you linking against OpenGL32.lib, which is part of the Windows SDK? This is the minimum required to get access to the basics so that you can then access the rest. I mentioned this in one of your previous questions.

Because of the way that C/C++ is, you must always expect to link against a library (a .lib file) unless the library is explicitly documented as being header only. The Windows SDK documentation for glClear also clearly states that you must link against OpenGL32.lib. The same is true for the various glColor and glRotate functions too. Just in case you are wondering, yes, Visual C++ makes sure to link against a couple of libraries by default. It links against the Visual C++ startup code, Visual C++ runtime, the STL, the Universal CRT, and the Windows Kernel32 library at the minimum.

If you want to carry on down the C/C++ path then you must get used to this. Lower level system calls get wrapped into helper libraries for other languages. More often than not, though, you end up running into the low level details in C/C++.