I have a RBD simulation I am exporting to FBX using the RBD to FBX tool. The simulation is fine
and everything, but the cracks in the mesh are much to visible.

I notice if I use the same workflow with a rounded mesh, I do not see the same cracks - it is perfectly smooth, until the mesh breaks of course. How could I do the same for other meshes?

Does your mesh have uv's?