Isolines are lines drawn on a curved surface to indicate that the surface exists. The Isolines variable controls how many isolines display on curved solids. The default value is 4. A larger number creates a more tightly curved object, as shown here.
- The Isolines and Dispsilh variables affect the plotting of shapes when the lines are hidden. Facet resolution (Facetres) sets the smoothness of shaded and rendered objects, and objects with hidden lines removed, as shown here.
- Type Regen to display the change, as required.
This information is taken from the training guide: AutoCAD® 2017 (R1): 3D Drawing and Modeling