3ds Max 2012 Bible - Kelly L. Murdock [255]
The Re-scale Time button fits all the keys into the active time segment by stretching or shrinking the number of frames between keys. You can use this feature to resize the animation to the number of frames defined by Start and End Time values.
The Key Steps group lets you set which key objects are navigated using key mode. If you select Use Track Bar, key mode moves through only the keys on the Track Bar. If you select the Selected Objects Only option, key mode jumps only to the keys for the currently selected object. You can also filter to move between Position, Rotation, and Scale keys. The Use Current Transform option locates only those keys that are the same as the current selected transform button.
Using Time Tags
To the right of the Prompt Line is a field marked Add Time Tag. Clicking this field pops up a menu with options to Add or Edit a Time Tag. Time Tags can be set for each frame in the scene. Once set, the Time Tags are visible in the Time Tag field whenever that time is selected.
Working with Keys
It isn't just a coincidence that the largest button in the entire Max interface has a key on it. Creating and working with keys is how animations are accomplished. Keys define a particular state of an object at a particular time. Animations are created as the object moves or changes between two different key states. Complex animations can be generated with only a handful of keys.
You can create keys in numerous ways, but the easiest is with the Key Controls found on the lower interface bar. These controls are located to the left of the Time Controls. Table 21.2 displays and explains all these controls. Closely related to the Key Controls is the Track Bar, which is located under the Time Slider.
Max includes two animation modes: Auto Key (N) and Set Key ('). You can select either of these modes by clicking the respective buttons at the bottom of the interface. When active, the button turns bright red, and the border around the active viewport also turns red to remind you that you are in animate mode. Red also appears around a spinner for any animated parameters.
Auto Key mode
With the Auto Key button enabled, every transformation or parameter change creates a key that defines where and how an object should look at that specific frame.
To create a key, drag the Time Slider to a frame where you want to create a key and then move the selected object or change the parameter, and a key is automatically created. When the first key is created, Max automatically goes back and creates a key for frame 0 that holds the object's original position or parameter. Upon setting the key, Max then interpolates all the positions and changes between the keys. The keys are displayed in the Track Bar.
Each frame can hold several different keys, but only one for each type of transform and each parameter. For example, if you move, rotate, scale, and change the Radius parameter for a sphere object with the Auto Key mode enabled, then separate keys are created for position, rotation, scaling, and a parameter change.
Set Key mode
The Set Key button (') offers more control over key creation and sets keys only when you click the Set Key button (K). It also creates keys only for the key types enabled in the Key Filters dialog box. You can open the Key Filters dialog box, shown in Figure 21.2, by clicking the Key Filters button. Available key types include All, Position, Rotation, Scale, IK Parameters, Object Parameters, Custom Attributes, Modifiers, Materials, and Other (which allows keys to be set for manipulator values).
FIGURE 21.2
Use the Set Key Filters dialog box to specify the types of keys to create.
Tutorial: Rotating a windmill's blades
The best way to learn is to practice, and there's no better time to practice than now. For this quick example, you animate a set