Description of issue

I got this error (on ubuntu 19.10, compiling from git):
/usr/include/osvr/Util/EigenQuatExponentialMap.h:164:31: error: ‘EIGEN_PI’ was not declared in this scope;

temporary SOLUTION :
add the following line on top of /usr/include/osvr/Util/EigenQuatExponentialMap.h
after the line including EigenCoreGeometry.h :
#define EIGEN_PI 3.141592654

hint:
before compiling from git clone, maybe try :
git submodule update --init --recursive