Custom Tangents

Unlike the presets shown so far, Custom tangents give you precise control, allowing you to essentially draw your own function curve. Let’s take a look.

1.  Edit Ø Fetch.

2.  Open the box’s Track View to the position track.

3.  Right-click the third key and change both the incoming and outgoing tangent types to Custom. You should now have handles on your function curves at this key.

4.  Drag the handles of one of the tangents and notice what this does to the function curve. You can try out different curves, then play the animation and see how the curves affect the motion.

	TIP Shift-drag a tangent handle to move the handles independently.

Notice that if the X or Y curve goes down, the box goes backward in that direction. You can get a fairly complex motion just by adjusting the tangents of one key.

5.  Edit Ø Fetch.

6.  Open the box’s Position track again.

7.  This time, change just the incoming tangent on the third key to the Slow In type.

8.  Change the outgoing tangent on the fourth key to the Custom type.

9.  By Shift-dragging the handle to the right of the flat line, create a function curve that looks like Figure 7.9.

FIGURE 7.9  Function curve to create

10.  Play the animation. This time the box stops and then anticipates the new motion before resuming.

11.  Save the file.

Applying Parameter Curve Out-of-Range Options

One of the last things we need to take a look at regarding the Track View and animation are the parameter out-of-range curve types. This simple and useful tool is used for animation that is repetitive in nature: for example, a spinning windmill, a rotating light beacon, or any animated sequence that is to be repeated throughout the duration of the animation.

One out-of-range type can be applied per track. It will automatically apply for the entire duration of the animation. The different out-of-range types can be seen in Figure 7.10 and are described in Table 7.3.

FIGURE 7.10  Tell your keys how to keep animating, once they get out of range, through this dialog box.

Creating a Block of Animation

Let’s take a closer look at using the Out-of-Range types on a track. First, we need to create a block of animation to repeat.

1.  Load the file windmill.max, which is shown in Figure 7.11 and can be found on the CD that came with this book.

FIGURE 7.11  A MAX windmill

2.  Select the windmill blades and lock your selection by pressing the spacebar.

3.  Go to frame 20 and turn on the Animate button.

4.  Rotate the blades 90º around the local Z axis.

5.  Turn off the Animate button.

6.  Play the animation.

Creating a Constantly Looping Animation

Obviously, the windmill turns for only 20 frames. Let’s use the out-of-range types to make this a constantly looping animation.

1.  Right-click the blade object and choose Track View Selected from the short-cut menu.

2.  Open the blade tracks to reveal the Rotation track. You should see the two keys that we just created.

3.  Select the rotation track.

4.  Click the Parameters Curves Out-of-Range button.

5.  Select the Loop type first by clicking in the Loop window. Notice that this automatically selects both the left and right arrows.

6.  Return to the viewport and press the Play button.

You’ll notice that with Loop, the windmill appears to come to a stop before looping the animation. If you watch even closer (watch the axis icon of the rotating object), you will see that the animation is not actually continuing around the remaining 270º. It is actually resetting itself, popping back the 90º and playing over.

Creating a Smoothly Continuing Animation

Let’s get the result we want by changing the out-of-range type.

1.  Select the rotation track again.

2.  Click the Parameter Curves Out-of-Range button.

3.  This time, choose the Relative Repeat type.

4.  Play the animation. This time the animation repeats relative to where it ends. This means that the second cycle of animation turns the blades another 90º tacked on to the first 90º. At the end of the second cycle, the blades have rotated 180º; the third cycle will add another 90º, and so forth.

Using Dummy Objects

Dummy objects (also called nulls) are a special type of object used in animation and hierarchical chains. You may recall that a dummy object is a type of helper object, an object that doesn’t appear in the render. Dummy objects are used for a variety of reasons and purposes. They function as reference points for other objects, provide ways of breaking down motion into more easily animatable components, and act as storehouses of information to relay to another link or expression.

	NOTE Dummies can be animated like any other object in MAX.

Using dummy objects can be very simple in some cases, or mind-boggling in a complex hierarchical animation. As with most things in 3D animation, it’s best to start with simple cases and work on understanding what is happening in these before building up to the very complex. Let’s look at some common uses of dummies. (Gee, sounds like the setup for a Dilbert cartoon...)

Providing a Handle

Say you want to animate a character’s eye movements. Rather than try to animate the rotation of each eye independently, you could assign Look At controllers to the eyes and assign a dummy as their target. The dummy will then function as a handle to drag the focal point of the eyes around as desired. This is exactly the function of the target of a target camera or target spotlight.

Another version of this is linking an object or sub-object to a dummy. The dummy can be used as an “end effector” in an IK chain or as a handle for controlling a sub-object selection.

	TIP Almost any object in MAX can be linked to a dummy object, including lights, meshes, patches, NURBS, and other dummies.

© 2000, Frol (selection, edition, publication)