The model looks like it might come from Google 3d Warehouse ie it originated in Sketchup??
It is a rather low poly mesh.ie its an approximation of the shape made with a limited number of planar faces. It is angular by nature like a cut diamond. In cg programs it can be made to look smooth when it is rendered. Unfortunately you wont be able to do something to this in SW to make it rounded.
You could however use the geometry as a reference to reconstruct the form by lofting between some representative cross sections, making use of splines and arcs etc.