In 2013, three undergraduates at the University of Southern California got together to design a web app for 3D modeling and rendering. It would work like Google Docs with realtime collaboration and use cloud-GPUs for fast rendering. We drafted a solution to the realtime collaborative editing problem using a selection-based locking system. The main advantage to our approach is that it avoids the need to implement complex operational transformations. We also described an abstraction layer that would allow any kind of mesh editing tool to be built with simple API calls to our system, without needing to consider concurrency problems at all.
By the time we finished this draft, others in the 3D software industry launched impressive products that accomplished everything we were hoping to do (particularly Clara.io and Autodesk 360) so we decided to forgo implementation and instead work on things that are more cutting edge.