How to hide the surface triangles of a Mesh so that only the outline is displayed.

Steps to Accomplish

1. Select all the Mesh elements that are to be affected
2. Open the keyin browser if not already open ( Utilities > Key-in )

3. key-in Facet Modify Hideedges ( Tool Setting- Minimum angle: 0 ) and except with a data point in the view

To re display the Mesh triangles, select all the Mesh elements to be affected and use the Facet Modify Hideedges Key-in with the Tool Setting ' Restore Hidden Edges ' checked. 

See Also

http://communities.bentley.com/products/microstation/w/microstation__wiki/10426.repair-a-mesh-element