Can I use a scalable terrain model for OpenRoads design?
There are two methods to export an OpenRoads Terrain from a Scalable Terrain Model:
First: In the Scalable Terrain Model dialog, the "File>Export STM to TM" command can be used to generate a Terrain from the entire Scalable Terrain Model. The exported terrain model can be used by OpenRoads. Using this tool, the size of the terrain model element is governed by the value, in MB, of the "STM_DOWNSAMPLING_PREFSIZE" configuration variable. The default is 5.
Second: In the Scalable Terrain Model dialog, the "Edit>Extract TM element" command can be used to generate a Terrain model from a specified area (Fence, Block, Element, etc...). This method will export all points within the selected area, so be aware that you might get an error message that the selected area is too big when using the "Extract TM element" tool. The number of points that can be stored in a Terrain Model is limited (typically less than 9 million points.)
Note that the Terrain created by both of these commands is a MicroStation Terrain element, and not yet completely an OpenRoads Terrain Model. In order to "civilize" the Terrain, run the "Set Feature Definition" command in the General Geometry task group and assign a Surface Feature Definition to the Terrain. This will also add the Terrain to the Civil Model tab in the Project Explorer.