Not found Eigen3_DIR when configuring a cmake project in Windows - c++

Question

I want to compile an open project, it needs Eigen3, I followed its guideline but stuck in this step:
"Set environment variable Eigen3_DIR to {YOUR_EIGEN3_DIRECTORY}/eigen3/cmake."
I have installed CMake gui and it printed following errors after configuration
Make Error at src/CMakeLists.txt:15 (find_package):
By not providing "FindEigen3.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "Eigen3", but
CMake did not find one.
Could not find a package configuration file provided by "Eigen3" with any
of the following names:
Eigen3Config.cmake
eigen3-config.cmake
Add the installation prefix of "Eigen3" to CMAKE_PREFIX_PATH or set
"Eigen3_DIR" to a directory containing one of the above files. If "Eigen3"
provides a separate development package or SDK, be sure it has been
installed.
But I have downloaded Eigen3 from here, and set the Eigen3_DIR as follows
So what should I do to fix it? I am just a beginner in cmake.

Answer 1

I am assuming you are using Windows. You will need Visual Studio installed. You can use the community version. You will need to do the following:
Create a directory called "build" within your Eigen directory.
Go to the build directory and do "cmake ..". This will create Visual Studio projects.
Load the .sln using Visual Studio.
Build the solution.
Ensure that the project called INSTALL was built also.
This will create the Eigen3Config.cmake file in your install directory. In my case the install directory was "C:\Program Files(X86)\Eigen3. Use this to as the value for Eigen3_DIR variable.
By default Eigen does not come with the Eigen3Config.cmake file. You will see Eigen3Config.cmake.in file. This is used to build the Eigen3Config.cmake file.
HTH