I like .ply, it's an easy format that supports vertex colors! .ply files are often used for point clouds, so it could be good to consider point cloud rendering when importing .ply files as well.

Might be able to find a nice library for this on here:
https://github.com/nothings/single_file_libs

Our eye tracking code is currently written in Python. It needs to be ported to C++ for both performance and integration reasons. PyTorch has a nice C++ API that is pretty much identical to the Python API. So most of the porting process won't be on changing the neural net but rather the code that invokes it.