Getting Started
with VNS 3: Lakes &
Streams
Part 6E. Terraffector Streambed
1. Open the Plan View Preferences to the Overlay/Gradient page,
and select Contours. This will make it easier to trace
a drainage.
2.We'll need room to digitize
the stream, so undock the Plan view and drag it out to
enlarge it.
3. Like Lakes, Streams
are a 2-step process. First, we'll dig a streambed into the terrain
with a linear Terraffector. Then we'll add a Stream.
4. Go to the Terrain Task
Mode, select the Terraffectors category, and Create
 .
5. Turn to the Mouse page
and select the Single drawing mode.
6. Click on the Plan view
titlebar to bring it forward if it's hidden. Start inside the
Lake vector in front of the Lake View Camera and
left-click points along low points in the terrain.
7. Right-click to finish and
name the vector Stream.
8. Add it to the Stream
Terraffector.
9. We could use one of the many
provided Components, but we're going to make our own. Close out
the Component
Gallery and dock the
Plan view.
10. Like an Area Terraffector,
a Terraffector uses a profile to control the way the terrain
affected. Unlike an Area Terraffector, a Terraffector is a linear
feature based on a vector line, not a closed vector shape. Edit
Cross-section Profile in the Terraffector Editor.
11. There is no default profile
here; we build it entirely from scratch. The leftmost point is
the vector. Terrain will be affected outward on both sides and
the ends based on this profile. Change the Value to -3
meters and Tension to 1. This is the centerline
of the streambed.
12. Add Point and click
on the graph, and repeat, to add 2 new points anywhere along
the profile. Change the Distance on the rightmost point
to 15 meters, make the Value 0, and change
the Tension to 1. This is the edge of the streambed.
Fifteen meters out from the vector the Terraffector will no longer
effect the terrain.
13. Select the second point and
change its Distance to 10 meters. Click and drag
it up to create a cross-section something like this. If you want
to move the point left or right, hold the Ctrl key down
while you click and drag.
14. Keep the profile and
go to the Elevation page. Change the Elevation Type
to Relative to Vector Elevation and Comparison
to Decrease Only.
15. Save the project and render
a preview.
16. If your streambed has sharp
turns in it, turn to the Terraffector Editor
General page and enable Spline Vectors.
17. Don't expect your first stream
to look as good as your first ocean. Streams are small features
that cut into terrain that usually doesn't have stream-size detail.
18. Alt+click the Stream
Vector in the Plan view to activate it.
19. Show Points 
from the toolbar to make them visible in the realtime Plan
view. By default, they're all selected and show up red.
20. To see what the vector profile
looks like, bring the Database Editor
forward and Edit Vector Profile  .
21. The Vector Profile Editor shows elevation on the vertical axis
and distance along the vector on the horizontal axis. The vector
is represented by the red line and the ground appears
in green. In this case, most of the vector is hidden behind
the terrain.
22. All the vertices are currently
active. Use the Next button to activate just the second
vertex, at the lake end of the stream. Increase the Vertex
Elevation to 2070 meters.
23. Render a preview. As expected,
the vertex has been raised high enough that the Terraffector
no longer has an effect at that point. The Terraffector is set
to decrease only so the terrain is not modified above its non-Terraffector
elevation.
24. Restore the profile
to its original state and close the editor.
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