This error is produced by the inability of the geometry parsing routine to resolve certain elements in the scene. These are typically very complex (eg: compound curves) or sometimes models imported from other software.
Option 1: Lower the Triangulation Level from ElumTools Settings (below).
Option 2: Simplify the calculation by setting materials and/or categories to "Ignore" in Material Mapping. See this blog post for some additional detail.
Option 3: Use Filter by View Visibility to remove complex geometry from the calculation. See this link for instructions.