I'm trying to build this project https://github.com/hemelb-codes/hemelb.
This project has several dependencies. I have several of them installed in my system but still cmake can't find them. The path of these dependencies installed in my system already have been added to the path in environmental variable. As far as I know when building a project which has several dependencies, these dependencies should be installed on the operating OS beforehand. I also downloadeded and built the dependencies into dependencies folder in project. Any idea why I can't build the project.

When ever there is issue with CMAKE builds I resort to either of the 2 solutions:

1. Manually create VS solutions and add files from repo then build
OR
2. Use vcpkg to auto install pre-build dependencies

If you plan to use the repo for longer time the added benefit is that you simply re-build with your own setup for each update and not needing to boggle with complex CMAKE syntax.

use CMake GUI so you can better check what's wrong or missing with your setup.

I used both vcpkg and CMake. The same issue is there. What is the dependencies folder is doing in the repo?

vcpkg is used with Visual Studio.

step 1:
install all deps with correct versions mentioned in the repo with vcpkg and then integrate it with visual studio.
vcpkg docs explain how to make vcpkg integration with VS.

step 2:
Create a VS solution and project file in the repo "Code" directory, open it and manually add all .h and .cpp files to new project.

then simply build your project file and VS will pick up all dependencies automatically.

In case if something doesn't work it should be easy to adjust things within VS project.
if some of the deps are not available in vcpkg then you'll have to create VS solutino and project for these too build and link manually.