3ds Max 2012 Bible - Kelly L. Murdock [270]
Caution
The object using the LookAt constraint flips when the target point is positioned directly above or below the object's pivot point. •
When you assign the LookAt constraint, the Create Key button for rotation changes to Roll. This is because the camera is locked to point at the assigned object and cannot rotate; rather, it can only roll about the axis.
You can use the LookAt constraint to let cameras follow objects as they move around a scene. It is the default transform controller for Target camera objects.
Orientation constraint
You can use the Orientation constraint to lock the rotation of an object to another object. You can move and scale the objects independently, but the constrained object rotates along with the target object. A good example of an animation that uses this type of constraint is a satellite that orbits the Earth. You can offset the satellite and still constrain it to the Earth's surface. Then, as the Earth moves, the satellite follows.
In the Orientation Constraint rollout, you can select several orientation targets and weight them in the same manner as with the Position constraint. The target with the greatest weight value has the most influence over the object's orientation. You also can constrain an object to the World object. The Keep Initial Offset option maintains the object's original orientation and rotates it relative to this original orientation. The Transform Rule setting determines whether the object rotates using the Local or World Coordinate Systems.
Using the Walkthrough Assistant
One alternative to using the Path and LookAt constraint is to use the Walkthrough Assistant. This tool is accessed from the Animation menu. It opens up a utility panel with several rollouts, as shown in Figure 22.6. Using this panel, you can create a new camera, select a path, and set the viewport to use the created camera. You can then use the View Controls rollout to cause the view to tilt to the left or right as you move through the path. This automates the process of getting a camera to follow a path.
FIGURE 22.6
The Walkthrough Assistant automates several constraints into a single interface.
The Walkthrough Assistant also includes a Render Preview that you use to see the results. If you drag the Time Slider to a different frame and click the Render Preview pane, the preview is updated. At specific frames, you can drag the Turn Head slider to change where the camera is looking. You can even tilt the camera up and down as well as side to side.
In the Advanced Controls rollout (which appears only after a camera has been created) are options for changing the Field of View and the Target Distance, which is useful if you're using a Depth of Field effect. You also can set the camera to move at a constant speed and an option to cause the camera to follow the path.
Understanding Controller Types
Controllers are used to set the keys for animation sequences. Every object and parameter that is animated has a controller assigned, and almost every controller has parameters that you can alter to change its functionality. Some controllers present these parameters as rollouts in the Motion panel, and others use a Properties dialog box.
Max has five basic controller types that work with only a single parameter or track and one specialized controller type that manages several tracks at once (the Transform controllers). The type depends on the type of values the controller works with. The types include the following:
• Transform controllers: A special controller type that applies to all transforms (position, rotation, and scale) at the same time, such as the Position, Rotation, Scale (PRS) controllers
• Position controllers: Control the position coordinates for objects, consisting of X, Y, and Z values
• Rotation controllers: Control the rotation values for objects along all three axes
• Scale controllers: Control the scale values for objects as percentages for each axis
• Float controllers: Used for all parameters with a single numeric value, such as Wind Strength and