Creating an efficient web interface for C++ library

As a starting point - I have a project, which consists of 4 following sub-projects:

• C++ library with C++ API,
• C++ Test project (library tests),
• Editor created in Qt/OpenGL, which uses C++ library,
• Editor testing project.

The C++ library is mainly responsible for managing a system of particles (to make it simple - basically it calculates new positions using specified set of rules). Editor created in Qt framework uses C++ library and it performs a visualization process (using OpenGL for rendering).

Going back to my question:

All operations (with rendering) are now performed locally. What I would like to do is to migrate it into cloud environment (C++ library calculation performed on the server-side, visualization in the web browser or in the editor properly adjusted for client-server application). What would be the best way of doing that, with the setup described above?

I've started to create a Python API for the C++ library (I need it anyway, so that I could use the library with Python) and I was thinking, about using Django/Flask for the Web development. Is that a good idea? Is it capable of utilizing rendering of various number of particles? (from 50k to 2M). Perhaps using WebGL and integrate it with Django would be a good idea?

PS. I am not really a JS enthusiast, so I would like to avoid using it.