Updated initial_cache.cmake.template

* Added BOOST_ROOT for Windows, since I've been using it for a while, and I think it works.
* Added EIGEN3_INCLUDE_DIR
* Changed all slashes to forward slashes

initial_cache.cmake.template

@@ -3,26 +3,33 @@
 # Boost:
 # -------
 # Windows: Download the pre-built binaries from http://sourceforge.net/projects/boost/files/boost-binaries/ for VS2015 (msvc-14 64bit).
-# Set the windows PATH variable to "<YOUR_BOOST_DIRECTORY>\lib64-msvc-14.0" and CMake will find it.
+# Either set the windows PATH variable to "<YOUR_BOOST_DIRECTORY>\lib64-msvc-14.0" and CMake will find it, or, set:
+#set(BOOST_ROOT "C:/boost" CACHE PATH "Boost search location" FORCE)
 # Linux: Boost can usually be installed via a package manager (e.g. apt-get install boost-all-dev) and this variable can be left uncommented.
 #set(BOOST_ROOT "/home/user/boost/install" CACHE PATH "Boost search location" FORCE)
 
+# Eigen3:
+# -------
+# Windows: Set to the path of the unzipped Eigen3 file.
+set(EIGEN3_INCLUDE_DIR "D:/eigen-10219c95fe65" CACHE PATH "Directory of the Eigen3 headers" FORCE)
+# Linux: Can be left empty when installed system-wide. (Note/Todo: Doesnt work with Eigen 3.0.5 from Ubuntu 12.04). Otherwise, set the path manually.
+#set(EIGEN3_INCLUDE_DIR "/home/user/eigen-10219c95fe65" CACHE PATH "Directory of the Eigen3 headers" FORCE)
 # Mechanism via ConfigLIB.cmake in 3rd party library directory
 # ==============================
 # OpenCV:
 # -------
 # Windows: Download the package from opencv.org, use 2.4.7.2 or never. It includes binaries for VS2013. Set this path accordingly.
-#set(OpenCV_DIR "C:\\opencv\\install" CACHE PATH "Location of OpenCVConfig.cmake" FORCE)
+#set(OpenCV_DIR "C:/opencv/install" CACHE PATH "Location of OpenCVConfig.cmake" FORCE)
 # Linux: Usually can be left blank but it can be used if OpenCV is not found.
 #set(OpenCV_DIR "/home/user/opencv/install/share/OpenCV" CACHE PATH "Location of OpenCVConfig.cmake" FORCE)
 #
 # Ceres:
 # -------
-#set(Ceres_DIR "C:\\ceres\\install-vs2015\\CMake" CACHE PATH "Location of CeresConfig.cmake" FORCE)
+#set(Ceres_DIR "C:/ceres/install-vs2015/CMake" CACHE PATH "Location of CeresConfig.cmake" FORCE)
 
 # Set the path to the python interpreter if you want to build the python bindings and it doesn't find it automatically:
 # ==============================
-#set(PYTHON_EXECUTABLE "C:\\Users\\user\\AppData\\Local\\Programs\\Python\\Python35\\python.exe" CACHE PATH "Path to the python interpreter." FORCE)
+#set(PYTHON_EXECUTABLE "C:/Users/user/AppData/Local/Programs/Python/Python35/python.exe" CACHE PATH "Path to the python interpreter." FORCE)
 
 # Set the path to the Matlab root directory if you want to build the Matlab bindings and it doesn't find Matlab automatically:
 # ==============================