C2086: 'int WINGDIAPI' : redefinition errors in Open Scene Graph?
The solution is: [Obtained from this website]
You need to add WIN32 to the defines in your project. In Visual Studio, right-click on your project, go to C/C++, Preprocessor, and in the Preprocessor Definitions field add WIN32 for both debug and release configurations. While you're at it, also add _DEBUG for the debug configuration and NDEBUG for the release configuration...
For some reason the default VS projects have no preprocessor definitions, even though these, at least, should almost always be used...