Chapter 10: Grouping and Linking Objects

Now that you've learned how to select and clone objects, you'll want to learn how to group objects together in an easily accessible form, especially as a scene becomes more complex. Max's grouping features enable you to organize all the objects that you're dealing with, thereby making your workflow more efficient.

Another way of organizing objects is to build a linked hierarchy. A linked hierarchy attaches, or links, one object to another and makes it possible to transform the attached object by moving the object to which it is linked. The arm is a classic example of a linked hierarchy: When the shoulder rotates, so do the elbow, wrist, and fingers. Establishing linked hierarchies can make moving, positioning, and animating many objects easy.

Working with Groups

Grouping objects organizes them and makes them easier to select and transform. Groups are different from selection sets in that groups exist like one object. Selecting any object in the group selects the entire group, whereas selecting an object in a selection set selects only that object and not the selection set. You can open groups to add, delete, or reposition objects within the group. Groups can also contain other groups. This is called nesting groups.

Creating groups

The Group command enables you to create a group. To do so, simply select the desired objects and choose Group Group. A simple Name Group dialog box opens and enables you to give the group a name. The newly created group displays a new bounding box that encompasses all the objects in the group.

Tip 

You can always identify groups in the Select by Name dialog box because they are surrounded by square brackets, and groups appear in bold in the Name and Color rollout of the Command Panel.

Ungrouping objects

The Ungroup command enables you to break up a group (kind of like a poor music album). To do so, simply select the desired group and choose Group Ungroup. This menu command dissolves the group, and all the objects within the group revert to separate objects. The Ungroup command breaks up only the currently selected group. All nested groups within a group stay intact.

The easiest way to dissolve an entire group, including any nested groups, is with the Explode command. This command eliminates the group and the groups within the group and makes each object separate.

Opening and closing groups

The Open command enables you to access the objects within a group. Grouped objects move, scale, and rotate as a unit when transformed, but individual objects within a group can be transformed independently after you open a group with the Open command.

To move an individual object in a group, select the group and choose Group Open. The white bounding box changes to a pink box. Then select an object within the group, and move it with the Select and Move button (keyboard shortcut, W). Choose Group Close to reinstate the group.

Attaching and detaching objects

The Attach and Detach commands enable you to insert or remove objects from an opened group without dissolving the group. To attach objects to an existing group, you select an object, select the Attach menu command, and then click on the group to which you want to add the object. To detach an object from a group, you need to open the group and select the Detach menu command. Remember to close the group when finished.

CROSS-REF 

Editable objects, like the Editable Poly, also can make use of an Attach feature, but attaching objects to an editable object permanently combines the objects together. You can learn more about the Editable Poly objects in Chapter 15, "Modeling with Polygons."

Tutorial: Grouping a plane's parts together

Positioning objects relative to one another takes careful and precise work. After spending the time to place the wings, tail, and prop on a plane exactly where they need to be, transforming each object by itself can misalign all the parts. By grouping all the objects together, you can move all the objects at once.

For this tutorial, you can get some practice grouping all the parts of an airplane together. Follow these steps:

1. Open the  T-28 Trojan plane.max file from the Chap 10 directory on the DVD. This file includes a model created by Viewpoint Datalabs.

2. Click the Select by Name button on the main toolbar (or press the H key) to open the Select by Name dialog box. In this dialog box, notice all the different plane parts. Click the All button to select all the separate objects, and click the Select button to close the dialog box.

3. With all the objects selected, choose Group Group to open the Group dialog box. Give the group the name Plane, and click OK.

4. Click the Select and Move button (or press W), and click and drag the plane. The entire group now moves together.

Figure 10.1 shows the plane grouped as one unit. Notice how only one set of brackets surrounds the plane in the Perspective viewport. The group name is displayed in the Name field of the Command Panel instead of listing the number of objects selected.

Figure 10.1: The plane moves as one unit after its objects are grouped.