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The Form group includes three options that determine how the terrain is formed: Graded Surface, Graded Solid, and Layered Solid. The Graded Surface option displays a surface grid over the contour splines; the Graded Solid adds a bottom to the object; and the Layered Solid displays each contour as a flat, terraced area. The Stitch Border option causes polygons to be created to close open splines by creating a single edge that closes the spline. The Retriangulate option optimizes how the polygons are divided to better represent the contours.

The Display group includes options to display the Terrain mesh, the Contour lines, or Both. You can also specify how you want to update the terrain.

The Simplification rollout lets you alter the resolution of the terrain by selecting how many vertical and horizontal points and lines to use. Options include using all points (no simplification), half of the points, a quarter of the points, twice the points, or four times the points.

Coloring elevations

The Color by Elevation rollout, shown in Figure 27.8, displays as reference the Maximum and Minimum Elevations. Between these is a Reference Elevation value, which is the location where the landmass meets the water. Entering a Reference Elevation and clicking the Create Defaults button automatically creates several separate color zones. You can add, modify, or delete zones using the Add, Modify, or Delete Zone buttons.

FIGURE 27.8

The Color by Elevation rollout lets you change the color for different elevations.

You can access each color zone from a list. To change a zone's color, select it and click the color swatch. You can set colors to Blend to the Color Above or to be Solid to Top of Zone.

Tutorial: Creating an island with the Terrain compound object

In this tutorial, you create a simple island. The Color by Elevation rollout makes distinguishing the water from the land easy.

To create an island using the Terrain object, follow these steps:

1. Select Create⇒Shapes⇒Ellipse, and drag in the Top view to create several ellipses of various sizes representing the contours of the island.

The first ellipse you create should be the largest, and the ellipses should get progressively smaller.

2. In the Left view, select and move the ellipses up and down so that the largest one is on the bottom and the smallest one is on top. You can create two smaller hills by including two ellipses at the same level.

Note

If you create the ellipses in the proper order from largest to smallest, then you can use the Select All command. If not, then select the splines in the order that they'll be connected from top to bottom before clicking on the Terrain button. •

3. Use the Edit⇒Select All (Ctrl+A) menu command to select all the ellipses, and select Create⇒Compound⇒Terrain.

The ellipses automatically join together. Joining all the ellipses forms the island.

4. In the Color by Elevation rollout, select a Reference Elevation of 5 and click the Create Defaults button.

This automatically creates color zones for the island. The elevation values for each zone are displayed in a list within the Color by Elevation rollout. Selecting an elevation value in the list displays its color in the color swatch.

5. Select each elevation value individually, and set all Zones to Blend to the Color Above option for all zones, except for the Zone with the lightest blue.

This creates a distinct break between the sea and the land of the island.

Figure 27.9 shows the final terrain. In an example later in this chapter, you'll use the Scatter compound object to add trees to the small terrain island.

Using the Mesher Object

You can use the Mesher compound object to convert objects to mesh objects on the fly as an animation progresses. This feature is useful for objects such as particle systems. After you convert the object to a mesh object, you can apply modifiers that weren't possible before, such as Optimize, UVW