Building a project that uses Chrono

When you develop a C++ project and you want to use the Chrono API, you need to:

• include the necessary .h headers at compile time,
• link the necessary .lib libraries at link time,
• dynamically link the necessary .dll libraries at run time,

as shown below:

This process can be made almost automatic if you use CMake for building your program, see below.

The CMake path is not the only option. For example, you could add Chrono libraries to your C++ project by manually inserting libraries in the IDE settings. However, the method described here is the one that we suggest in most cases since it is platform-independent as it draws on the CMake build tool.

## 1) Check prerequisites:

• CMake must be already installed on your computer.
• Chrono must be already installed and built on your computer, as explained here.

## 2) Create the project directory

• Copy the template_project directory to some place and rename it as you like. For example copy from C:\chrono_source\template_project to C:\my_project_source

This will be the directory where you put your source code.

## 3) Edit the CMake script

• In the template directory there is already a CMakeLists.txt script. It will be used by CMake. Optionally you might edit it, see below.
For example, suppose you want to use also the POSTPROCESS module. You can edit CMakeLists.txt where it reads:

find_package(Chrono
COMPONENTS Irrlicht
CONFIG)

and add the required module:

find_package(Chrono
COMPONENTS Irrlicht Postprocessing
CONFIG)

The same is done for other modules: FEA, Matlab, Vehicle, Cosimulation, etc.

If you prefer to change the name of the default my_example.cpp to something more meaningful, say my_simulator.cpp, just rename that file and then change the line
add_executable(myexe my_example.cpp)
into
add_executable(myexe my_simulator.cpp)
If your program is split in multiple .cpp sources, simply list them in this line: add_executable(myexe my_simulator.cpp my_foo_source.cpp my_bar_source.cpp)

## 4) Start CMake

• Start the CMake GUI
• Use Browse source... by setting the source directory that you created, ex: C:\my_project_source
• Use Browse build... by setting a new empty directory for the output project, ex: C:\my_project_build

## 5) Configure

• Press the Configure button in CMake
• When prompted to pick a generator, select the same compiler that you used to compile Chrono
• Important: set the Chrono_DIR variable. This is the cmake directory that you find in the directory where you built Chrono. In our example it is C:/chrono_build/cmake
• Press the Configure button again

## 6) Generate the project

• Press the Generate button in CMake. A project will be created in the build directory. In our example you will find it in C:\my_project_build

## 7) Compile the project

If you used a VisualStudio generator in CMake,

• Open the solution in VisualStudio editor (in our example double click on C:\my_project_build\my_project.sln)
• Change from Debug to Release mode, using the drop-down list in the toolbar of VisualStudio
• Use the menu BUILD / Build solution... to compile and link.

If you used a Unix makefile generator in CMake (ex. in Linux), you can open a shell, cd into the build directory and call make:

cd /home/john/my_project_build
make

## 8) Run your program

By default all binaries (ex. myexe.exe) of your project will go into your build directory, in our example C:\my_project_build\Release\my_project.sln (or C:\my_project_build\Debug\my_project.sln if you decided to compile in Debug mode).

• double click on the .exe file and you should see the demo running in an interactive 3D view

• To make things simple, at the end of the default CMakeFile.txt used in this example there is this instruction: add_DLL_copy_command macro. This takes care of automatically copying all the needed dlls right after each build. It also copies the Irrlicht.dll into your executable directory, if the Irrlicht module is used.
If you followed the Chrono install tutorial for Visual Studio you will eventually end up with two folders inside C:/chrono_build/bin/, namely /Release and /Debug.
Currently, the add_DLL_copy_command macro will pick the dlls only from the /Release subdirectory.
This is perfectly fine if your project is built in Release too, but it will crash if built in Debug!
In order to run your applications in Debug mode you have to manually copy any dll inside C:/chrono_build/bin/Debug into your C:/my_project_build/bin/Debug folder (Irrlicht.dll included).