Creating a Scatter Object

A Scatter object spreads multiple copies of the object about the scene or within a defined area. The object that is scattered is called the Source object, and the area where the scatter objects can be placed is defined by a Distribution object.

CROSS-REF 

Particle systems, which are discussed in Chapter 35, "Creating Particles and Particle Flow," can also create many duplicate objects, but you have more control over the placement of objects with a Scatter object.

To create a Scatter object, choose an object that will be scattered over the surface and select the Create Compound Scatter menu command. The selected object becomes the Source object. A rollout then opens, in which you can select the Distribution object or use defined transforms.

Under the Scatter Objects rollout, the Objects section lists the Source and Distribution objects. Name fields are also available for changing the name of either object. The Extract Operand button is available only in the Modify panel; it lets you select an operand from the list and make a copy or instance of it.

Working with Source objects

The Source object is the object that is to be duplicated. Figure 18.11 shows a Cylinder primitive scattered over a spherical Distribution object with 500 duplicates. The Perpendicular and Distribute Using Even options are set.

Figure 18.11: A Scatter object made of a Cylinder spread over an area defined by a sphere

In the Scatter Objects rollout are several parameters for controlling the Source object. In the Source Object Parameters section, the Duplicates value specifies how many objects to scatter. You can also specify a Base Scale and the Vertex Chaos values. The Base Scale is the value that the object is scaled to before being scattered. All new objects are scaled equally to this value. The Vertex Chaos button randomly distributes the object vertices.

The Animation Offset defines the number of frames between a new duplicate and the previous one.

Note 

If you look closely at a Scatter object, you'll notice that both the Source and Distribution objects have the same object color. To color them differently, use the Multi/Sub-Object Material.

Working with Distribution objects

To select a Distribution object, click the Pick Distribution Object button and select an object in the viewport. (Make sure that the Use Distribution Object option is selected in the Scatter Objects rollout.) You can specify the Distribution object as a Copy, Instance, Reference, or Move.

Under the Distribution Object Parameters rollout are several options for controlling the Distribution object. The Perpendicular option causes the Source objects to be aligned perpendicular to the Distribution object. If the Perpendicular option is disabled, the orientation remains the same as that of the default Source object. Figure 18.12 shows the same Scatter object as in the preceding figure, but with several different options.

Figure 18.12: A Scatter object with different options: Base Scale at 20%, Vertex Chaos at 2.0, Perpendicular option disabled, and Duplicates at 100

The Use Selected Faces Only option enables you to select the faces over which the duplicates are positioned. The Selected Faces are those passed up the Stack by the Mesh Select modifier.

Other Distribution object parameter options include Area, Even, Skip N, Random Faces, Along Edges, All Vertices, All Edge Midpoints, All Face Centers, and Volume. The Area option evenly distributes the objects over the surface area, and the Even option places duplicates over every other face. The Skip N option lets you specify how many faces to skip before placing an object. The Random Faces and Along Edges options randomly distribute the duplicates around the Distribution object. The All Vertices, All Edge Midpoints, and All Face Centers options ignore the Duplicates value (which specifies the number of duplicates) and place a duplicate at every vertex, edge midpoint, and face. Figure 18.13 shows several of these options.

All the options described thus far place the duplicates on the surface of the object, but the Volume option scatters the duplicates inside the Distribution object's volume.

Figure 18.13: A Scatter object with different distribution options: Area, Skip N where N=7, Random Faces, All Vertices, and All Face Centers

Setting Transforms

The Transforms rollout is used to specify the individual transformation limits of the duplicate objects. For example, if the Z-axis value is set to 90, then each new duplicate is randomly rotated about its local Z-axis at a distance somewhere between −90 and 90.

You can use these transformations with a Distribution object or by themselves if the Use Transforms Only option is selected under the Scatter Objects rollout. The Use Maximum Range option causes all three axes to adopt the same value. The Lock Aspect Ratio option maintains the relative dimensions of the Source object to ensure uniform scaling.

Speeding updates with a proxy

Working with a large number of duplicates can slow the viewport updates to a crawl. To speed these updates, select the Proxy option in the Display rollout. This option replaces each duplicate with a wedge-shaped object. For example, if you used the Scatter object to place people on a sidewalk, you can use the Proxy option to display simple cylinders in the viewports instead of the details of the person mesh.

Another way to speed the viewport updates is to use the Display spinner. Using this spinner, you can select a percentage of the total number of duplicates to display in the viewport. The rendered image still uses the actual number specified.

The Hide Distribution Object option lets you make the Distribution object visible or invisible. The Seed value is used to determine the randomness of the objects.

Loading and saving presets

With all the various parameters, the Load/Save Presets rollout enables you to Save, Load, or Delete various presets. You can use saved presets with another Source object.

Tutorial: Covering the island with trees

You can combine several different types of compound objects to create interesting effects. In this tutorial, we use the Scatter object to add trees to the Terrain object island created earlier in this chapter.

To add trees to the island with the Scatter object, follow these steps:

1. Open the  Island terrain with trees.max file from the Chap 18 directory on the DVD.

   This file is the same island terrain example that you completed earlier in this chapter, but it also has a simple tree added to it.

2. With the tree object selected, select the Create Compound Scatter menu command.

3. Click the Pick Distribution Object button, and select the island terrain. Set the number of Duplicates to 100, and disable the Perpendicular option.

   All the trees now stand upright.

4. Select the Random Faces option.

   The trees become denser around the hills where there are more faces.

Figure 18.14 shows the island with the trees.

Figure 18.14: Using the Scatter object, we can add trees to our island terrain