You want to create an interactive 3D terrain but you have only one source of input: either an elevation model or an orthophoto. It this case it is still possible to get your data in Virtual Surveyor, but you will not have the full 3D potential.
It is important to know that the 'Create terrain' button will become enabled as soon as the minimum input in complete.
Only an elevation model
As soon as you create a terrain with only elevation information, a slope color map will be added automatically after the terrain creation process completes.
Such a terrain can be used to calculate volumes, generate breaklines and perform other types of analysis. In case you switch off the slope layer in the ProjectTree, you will get a black screen.
You can also use Terrain Contours, Terrain Colors and Slope Directions to visualize the elevation layer. You can find those functions in the Analysis tab.
Only an orthophoto
With only an orthophoto available, a terrain will be created that is flat as shown in the illustration below. By default, the elevation will equal to 0 but you can use the background value to set a different elevation level.
Although your project will be flat, you can still load 3D models on top of it, fly around, create movies etc.