Problem: Certain CAD layers fail to display properly in ArcScene (polyface and polymesh)
This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.
In ArcScene, some three-dimensional polyface-based CAD data displays flat, as if there are no z-values. Additionally, some polymesh-based entities do not display at all.
This is a known issue.
Solution or Workaround