Before using
Site Designer tools to create site elements, create or import a toposurface in the
Revit model, and set the base toposurface for use with
Site Designer.
Create a Toposurface for Site Designer
Create or import a representation of the existing toposurface in the Revit model, then use the Set Base Toposurface tool to create a copy of the toposurface for use with Site Designer.
Convert a Mass to a Toposurface
To convert a conceptual mass to a Revit toposurface for use with Site Designer, use the Toposurface Conversion tool.