Hi Sophie,
SAM's 3D Shade Calculator is part of the SAM project. The source code files are named s3[...].cpp like s3engine.cpp, s3objects, etc. in the src folder:
github.com/NREL/SAM/tree/develop/src
It is distributed as part of SAM, not as a standalone project.
The best way to explore all of the available models in SSC is to use SDKtool as described on the SDK page. With SDK you can see a list of all of the modules, show the inputs and outputs of each module, and write scripts to run the modules:
sam.nrel.gov/software-development-kit-sdk
You can also browse the list of files in the ssc folder of the SSC project -- compute module names are preceded by "cmod_". For example, the pvsamv1 module (Detailed Photovoltaic Model in the SAM user interface) code is in cmod_pvsamv1.cpp:
github.com/NREL/ssc/tree/develop/ssc
Best regards,
Paul.