Align Graph to Terrain. Seems pretty easy, unless you've ended up in a situation where your streets are digging ruts in your reference terrain as you draw them. So naturally, you try to move them up the y-axis (vertically) with the MOVE tool. The geometry moves, but your terrain is still, well, looking depressed.
When you draw a street (graph) element, its elevation is determined a) by the reference terrain you have active (checked) in the SCENE window and b) whether "align terrain" is checked in the Street Creation Settings: go to Graph > Street Creation Settings, and find the Align Terrain box under General.
Here are some results.
A. Reference terrain ON, box CHECKED. Geometry is fully visible, terrain layer intact.
B. Reference terrain layer ON, box UNCHECKED. Geometry is partly obscured, terrain layer intact.
C. Reference terrain layer OFF, box checked. Geometry is fully visible, terrain layer modified.
D. Reference terrain layer on, box unchecked. Geometry is obscured, terrain layer unmodified.
Now try the align streets to terrain tool (or Graph > Align Graph to Terrain) with these street segments after clicking the node at the middle of each roundabout. Align function: Project All, Heightmap: Terrain Elevation (or the name of your terrain reference layer).
- A, B and C: Nothing happens.
- D: The geometry aligns to the terrain and your layer has no "ruts".
Play with these settings and think about when in your process you are going to bring in your street graph or draw additional streets. Is it better to start everything at zero elevation, then align everything to the terrain later?
Oh... and since we're modeling in three dimensions: if you select y=0 as your height map, your selected geometry will drop down to zero elevation, indicated by the grid "floor". That may be a long way down depending on the place you are modeling.
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