3ds Max 2012 Bible - Kelly L. Murdock [269]
To move an object in a figure eight, follow these steps:
1. Open the Figure skater skating a figure eight.max file from the Chap 22 directory on the CD.
This file includes a figure skater model imported from Poser and two dummy objects. The figure skater is linked to the first dummy object (the one initially closest to the skater).
2. Click the Auto Key button (or press the N key), drag the Time Slider to frame 100, and rotate the first dummy object two full revolutions in the Top viewport.
3. Select the second dummy object, and rotate it two full revolutions in the opposite direction. Click the Auto Key button again to deactivate it.
Tip
If you enable the Angle Snap Toggle button on the main toolbar, then it is easier to rotate objects exactly two revolutions. •
4. With the figure skater selected, choose Animation⇒Constraints⇒Link Constraint. Then click the first dummy object (the top one in the Top viewport).
The Link constraint is assigned to the figure skater.
5. In the Link Params rollout, click the Add Link button. With the first dummy object selected in the viewport, set the Start Time value to 0. Then click the second dummy object, and set the Start Time to 25 in the Link Params rollout. Finally, click the first dummy object again, and set the Start Time to 75.
6. Click the Play Animation button (or press the / key) to see the animation play.
Tip
Another way to accomplish this same motion is to create a spline of a figure eight and use the Path constraint. •
Figure 22.5 shows the skater as she makes her path around the two dummy objects.
FIGURE 22.5
With the Link constraint, the figure skater can move in a figure eight by rotating about two dummy objects.
LookAt constraint
The LookAt constraint won't move an object, but it rotates the object so it is always orientated toward the target object. For example, you could use the LookAt constraint to animate a character's head that is watching a flying bumblebee. It is also very useful to apply to camera objects that follow a specific object throughout the animation.
After you select a target object, a single line extends from the object and points at the target object. This line, called the Viewline, is visible only within the viewports.
The LookAt Constraint rollout, like many of the other constraints, includes a list of targets. With the Add and Delete LookAt Target buttons, you can add and remove targets from the list. If several targets are on the list, the object is centered on a location between them. Using the Weight value, you can cause the various targets to have more of an influence over the orientation of the object. The Keep Initial Offset option prevents the object from reorienting itself when the constraint is applied. Any movement is relative to its original position.
You can set the Viewline length, which is the distance that the Viewline extends from the object. The Viewline Length Absolute option draws the Viewline from the object to its target, ignoring the length value.
The Set Orientation button lets you change the offset orientation of the object using the Select and Rotation button on the main toolbar. If you get lost, the Reset Orientation button returns the orientation to its original position. You can select which local axis points at the target object.
The Upnode is an object that defines the up direction. If the LookAt axis ever lines up with the Upnode axis, then the object flips upside-down. To prevent this, you can select which local axis is used as the LookAt axis and which axis points at the Upnode. The World is the default Upnode object, but you can select any object as the Upnode object by deselecting the World object and clicking the button to its right.
To control the Upnode, you can select the LookAt option or the Axis Alignment option, which enables the Align to Upnode Axis option. Using this option, you can specify which axis points toward