The Span Curve Visibility commands are available by right-clicking (on a visible layer, in the viewer when in the Mesh workspace) a master topology line, a topology line, or a refined mesh line. These commands control the visibility of the span curves. A span curve is a line that passes through corresponding master topology nodes across layers. Span curves are used to construct the 3D mesh. A span curve that is sharply curved can indicate a potential problem with mesh quality.
The Toggle span curve visibility command toggles the visibility of the span curve that passes through the nearest node of the master topology.
The Turn on all span curves and Turn off all span curves commands control the visibility of all span curves at once.