Probably the best way to get a vegetation grid is a difference grid between the DSM and DTM (DSM- DTM).
If you only have a DSM or DTM, a surrogate vegetation grid can be created from the Derivative Grids menu choice on the Calculate Menu or Raster GIS menu,
It must have the same size and spacing as the DEM it is used with, and if you change the DEM, you must change the vegetation grid. If it does not match, you will be asked if you want to reproject it to match the DEM. You should be careful in using this option, that the vegetation covers the entire DEM, and that its spacing is appropriate.
This will only be valid to the degree that the land classification categories (or shapefile regions) have uniform vegetation (or other obstacles). If they do not, you are responsible for using the data anyway, not using any vegetation grid, or creating a better alternative. Nothing replaces the need for a careful analysis of the situation.
These can be loaded and used for intervisibility masking.
Option when loading the vegetation grid to show its map or not; on Import/Export tab of options form
Turn on/off rapidly
Edit grids using any Edit menu option.
Last revision 11/14/2011