Build breaks with Eigen 3.3~beta1-2 (default for Ubuntu 16.04 / latest Mint)

[Algomorph]

This is a bug that occurs on both the master and new_pangolin branches, using either Steven Lovegrove's version of Pangolin or arpg/Pangolin (same effect), and using Eigen 3.3~beta1-2, provided by universe PPA on Ubuntu 16.04-based systems (default). There is a workaround, provided below.

During compile, I'm getting:

In file included from /usr/include/eigen3/Eigen/Core:367:0,
                 from /usr/local/include/pangolin/gl/gl.h:39,
                 from /usr/local/include/pangolin/pangolin.h:33,
                 from /home/algomorph/Garage/ARPG/SceneGraph/include/SceneGraph/GLinclude.h:3,
                 from /home/algomorph/Garage/ARPG/SceneGraph/include/SceneGraph/GLHelpers.h:12,
                 from /home/algomorph/Garage/ARPG/SceneGraph/include/SceneGraph/FBO.h:4,
                 from /home/algomorph/Garage/ARPG/SceneGraph/include/SceneGraph/SimCam.h:4,
                 from /home/algomorph/Garage/ARPG/SceneGraph/src/SimCam.cpp:1:
/usr/include/eigen3/Eigen/src/Core/Matrix.h: In instantiation of ‘Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>::Matrix(const T&) [with T = pangolin::OpenGlMatrixSpec; _Scalar = double; int _Rows = 4; int _Cols = 4; int _Options = 0; int _MaxRows = 4; int _MaxCols = 4]’:
/home/algomorph/Garage/ARPG/SceneGraph/include/SceneGraph/SimCam.h:163:186:   required from here
/usr/include/eigen3/Eigen/src/Core/Matrix.h:296:31: error: no matching function for call to ‘Eigen::Matrix<double, 4, 4>::_init1(const pangolin::OpenGlMatrixSpec&)’
       Base::template _init1<T>(x);

Following a similar bug report here, I found that a simple workaround is:

1. Clone Eigen mirror from here.
2. git checkout tags/3.1.2
3. (Optional) git checkout -b ver 3.1.2
4. Recompile Pangolin after setting EIGEN_INCLUDE_DIR to your eigen repository directory in CMake
5. Recompile SceneGraph after setting EIGEN_INCLUDE_DIR to your eigen repository directory in CMake

[crheckman]

@Algomorph thanks for your helpful writeup. Could you test @crmauceri's fix that's in #23?

[Algomorph]

@crheckman , unfortunately, I cannot, since I'm blocked by #24 on branch fix/eigencompatiblity.

[crheckman]

@Algomorph #24 should be "fixed." There are many ways to address that issue, but the most compatibility-ensuring ones require inheriting a value that Bullet defines in a preprocessor directive BT_USE_DOUBLE_PRECISION which has routinely interfered with my happily living. Since the applications that use Bullet are only examples, I don't think it's worth dragging in that kind of nonsense.

[Algomorph]

@crheckman oh, that's great. I may not remember correctly, but I thought I didn't find away to disable it from using bullet / examples. If this bullet thing no longer affects fix/eigencompatibility or you can tell me how to disable building the bullet stuff, and you still would like for me to test the fix on Ubuntu 16.04, let me know.

[Algomorph]

@crheckman , I've tested fix/eigencompatibility, #23. The library compiles with the new Eigen. I still cannot build the examples that depend on bullet (so I suggest you reopen #24), but that doesn't matter to me.