The raw mesh received from the Hololens Spatial Mapping component is overly complex and may have holes and ghost geometry. The raw mesh is not very usable especially if one has to use the mesh as a surface for driving vehicles or other physics based simulations.
Hololens apps from Microsoft Studio like Fragments and Young Conker use some very neat C++ native code to dynamically refine the mesh.
Update: Asobo Studio has released the Spatial Understanding component as a dll that will now help with the mesh as well as other spatial queries.
We took a shot at refining the mesh in C# and here are our results.