CMake find_package() cannot find OpenSim

[martinandrovich]

After following the guide and successfully building and installing OpenSim on my Ubuntu 18.04 machine via the super build approach, there was an error when trying to find the package in CMakeLists.txt:

By not providing "FindOpenSim.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "OpenSim", but
CMake did not find one.

Could not find a package configuration file provided by "OpenSim" with any
of the following names:

  OpenSimConfig.cmake
  opensim-config.cmake

Add the installation prefix of "OpenSim" to CMAKE_PREFIX_PATH or set
"OpenSim_DIR" to a directory containing one of the above files.  If
"OpenSim" provides a separate development package or SDK, be sure it has
been installed.

The issues can be resolved by adding the following (with ~/opensim/ being the install directory):

set(OpenSim_DIR "~/opensim/lib/cmake/OpenSim")
find_package(OpenSim REQUIRED)

It would be nice if the guide mentioned a proper way of handling this or added a FindOpenSim.cmake file to be run with some environment variable.

[chrisdembia]

Hey @martinandrovich, FindOpenSim.cmake is an older mechanism, and I think using an OpenSim Config file is more appropriate.

Specifying OpenSim_DIR or CMAKE_PREFIX_PATH in downstream projects is standard practice with CMake.

We give a tip about this here:

opensim-core/cmake/SampleCMakeLists.txt

Lines 17 to 21 in 2f5d4b0

	# This depends on OpenSimConfig.cmake being located somewhere predictable
	# on your machine. If you have installed it somewhere that CMake won't be
	# able to guess, you'll need to tell find_package where to look (with the PATHS
	# or HINTS parameters), or specify the installation directory in the
	# CMAKE_PREFIX_PATH variable.

[martinandrovich]

Oh okay, was not aware of that (not a CMake power-user to be honest), thanks @chrisdembia . And yes, I found that sample file as well, but I thought that running the install command would actually make the config file available for CMake without having to do it manually.

[chrisdembia]

Any suggestions for how we can make the instructions/documentation/sample clearer?

[martinandrovich]

The guide was actually fine; maybe an example in the end of how to use OpenSim with CMake would be helpful, or at least a mention or reference to the SampleCMakeLists.txt file.

Also, I noticed that the OPENSIM_COPY_DEPENDENCIES configuration option does not show up per default when using the CMake GUI (it is hidden under advanced, but set to true).

An apt install opensim option would be amazing for Ubuntu users, but in the meanwhile I wrote a small bash script to automate the installation process (it's missing some dependency stuff and thorough testing). I think you could add a section for a "quick install" for Ubuntu 18 as well, like you have for other versions of Ubuntu.