CHAPTER 14
Manipulating Scenes with Maxscript

Featuring

•  Scripting Objects

•  Accessing Global Object Properties

•  Replicating Objects

•  Creating Materials

•  Scripting Modifiers and Options

•  Creating and Managing a Hierarchy

•  Using Environment and Render Effects

•  Working with Splines

•  Working with Meshes

One of the primary uses of MAXScript is to work with scene objects, creating, modifying, and automating any task that can be done with the objects.

In this chapter you will learn about some of the MAXScript tools you can use to manipulate scenes and work with objects in MAXScript. Throughout the chapter you will have an opportunity to try out what you’ve learned by creating some actual scripts.

Scripting Objects

Using MAXScript you can create and modify almost everything in MAX. There are some restrictions, which are the same restrictions that apply to the Macro Recorder (see “Macro Recorder Limitations” in Chapter 13).

Working with objects in MAXScript takes advantage of the object-oriented behavior of 3D Studio MAX. Let’s see how.

Creating an Object and Accessing Its Properties

You can create objects in MAXScript by just assigning an object to a variable. It’s as simple as typing a = box(). If you do so, a default-size box (25x25x25) will be created. This way, you can create every primitive, helper, camera, light, and so forth. Complex objects, such as editable meshes, splines, patches, NURBS, and compound objects, require different commands.

As soon as you assign an object to a variable (or create an object by assigning it), you can access any object property using this variable. The property will be valid until the object is deleted, the variable is redefined, or MAX is restarted.

	TIP If you want a variable to be saved with a scene, you need to use Persistent Global variables. See Chapter 17 for more information.

When you create a simple object, as in the box example above, it’s created with a default size, position, etc. You will most likely want to access and change this data. But in order to do so, you need to know which data is available for you. Why? Because each and every object has different properties. For instance, a sphere has a radius, but a box has height, length, and width. To list an object’s properties, you use the SHOWPROPERTIES command. Once you have typed a = box(), then if you type showproperties a MAXScript will list the properties in the Listener, as shown in Figure 14.1.

FIGURE 14.1  SHOWPROPERTIES result

You can access any of this box’s properties by typing a.property (for example, a.height). You can also change the values of each property, typing a.property = value (a.height = 60).

You can set an object property at the time of creation, specifying the properties and their

 values: a = box height:60 width:30 length:40

There’s no limit in the number of properties you can define, and if any property is not listed, it will be set to its default value. If a property is listed but does not relate to that object, it’s discarded.

	TIP Besides using SHOWPROPERTIES, you can also record creating an object and changing its parameters to the values you need. This makes it easier for you to manipulate objects, and keeps you from having to memorize thousands of commands.

Accessing an Object by Name

Sometimes you do not create objects in MAXScript, but you need to process objects already created. To do so, you need to learn how to select and manipulate selections, and how to refer to objects by name.

You can access any object by its name simply by adding the $ symbol before the object name. For instance if you have an object named “Wall,” you can access it using $wall.

	NOTE Object names in MAXScript are not case-sensitive. If you have two objects, one named “Ball” and another named “ball” (and MAX, unfortunately, allows you to name as many objects as you wish with the same name), MAXScript will not distinguish between them even if you use $ball or $Ball.

You can also assign variables that point to named objects in the scene, like a = $wall. From then on, you can access the object as a or as $wall.

	WARNING If the object is renamed, you cannot use $name any more. But if you assign $name to a variable and later rename the object, this variable can be used. For example, you could create a box named “Box01”, type var = $box01, and then rename “Box01.” If you type var, MAXScript shows you the box properties; if you type $Box01 it returns undefined.

Working with Selections

Sometimes you don’t know a specific object name, or you do not want to use a specific object, but you want to use an object selection. You can refer to selections in two ways: using selection, which is an array of all selected objects, or using the $ symbol.

There are some peculiarities in selections that need to be addressed. It is very important to know how many objects have been selected, using $.count or selection.count. This is important because if selection.count returns only one object selected, this object can be accessed simply using $. On the other hand, if it returns more than one object, you must use selection[i] to access each object in the selection array.

Manipulating Selections

You can manipulate selections by adding or removing objects from the selection. To remove an object from the selection, use the DESELECT command; to add objects to a selection, use the SELECTMORE command. To simply discard any selection and select a specific object, you can use the SELECT command.

	TIP You can use wildcards when specifying object names. For instance, if you want to select all objects that start with “B”, you can use select $B*. If you want to select all objects that end in “01” you can use $*01. You can also use the “?” wildcard to represent a single character.

© 2000, Frol (selection, edition, publication)