Often, urban areas are designed with contour lines etc. Thus, it would be great to support TINs for terrain representation instead of raster data / bitmaps only.
As well as TIN support it would be useful to have esri raster dataset (Grid file) support where the elevation values were read directly, rather than colour values having to be read). This would allow DEM's created in arcGIS to be accessed directly.
Be able to edit the terrain, is a main issue for an urban designer. DTMs are available typical as ascii grid files and will therefore be great if that could be supported