The Relative Error option for Face Spacing and Edge Spacing allows the edge length on particular faces or edges to vary depending upon the local curvature. That is, a short edge length is used where the face or edge is highly curved, and a longer edge length is used where it is flatter. It is used for automatically refining the mesh in geometries that have curved faces or edges and can replace the need for other Controls in such geometries. It has a similar effect to using the Angular Resolution setting, but is specified differently.

In order to control how much the curvature is resolved, you must set the Relative Error. The Relative Error is the maximum deviation of the resulting mesh away from the geometry face or edge expressed as

where r is the local radius of curvature. The value entered should be in the range of approximately 0.00004 to 0.292, which corresponds to 360 edges and 4 edges per circumference, respectively. When the Relative Error is made smaller, more nodes will be placed on the edge or face to resolve the curvature better.