Urho3D/IK/IKConverters.h:28:10: fatal error: ‘ik/quat.h’ file not found

I use Urho3D-1.7.1-macOS-64bit-STATIC.tar.gz. But there are a lot of header files missing. How can I solve it? Do I need to copy in the source directory?

I think you need to add the ThirdParty folder into your include paths. Not just the include directory. Because the headers are included relative to that.

Also, as many will end up suggesting is to use the code straight from repository as it is (likely) more stable. Unless you need to maintain some kind of compatibility. Maybe even disable some of the features you don’t need (like one or both scripting components for example or databases).