That looks like your render mesh needs to be denser. Chage it in either Options>Document Properties>Mesh for the entire scene or select an object and adjust it in the Properties panel>Render Mesh Settings>Adjust. It may also be that the surface needs to be split at it’s tangents to become a polysurface. If that’s the case and you don’t have surface edges at the sharp corners, use the command DivideAlongCreases.