3ds Max 2012 Bible - Kelly L. Murdock [399]
You open the Key dialog box, shown in Figure 37.15, by selecting a key and right-clicking the key. It lets you specify two different types of tangent points: Continuous and Discontinuous. Continuous tangents are points with two handles on the same line. The curvature for continuous tangents is always smooth. Discontinuous tangents have any angle between the two handle lines. These tangents form a sharp point.
By default, all tangents are continuous and move together, but you can break them apart to be discontinuous by clicking the Break Tangents button in the Tangent Actions toolbar. This lets each handle be moved independently. Broken tangents can be locked together again with the Unify Tangents button, so they move together. This unifies the tangent handles even if they don't form a straight line.
New Feature
The Break and Unify Tangents buttons are new to 3ds Max 2012. •
Tip
Holding down the Shift key while dragging a handle lets you drag the handle independently of the other handle. •
FIGURE 37.15
The Key dialog box lets you change the key's Time, Value, or In and Out tangent curves.
The Lock Tangents button in the Key Info dialog box lets you change the handles of several keys at the same time. If this button is disabled, adjusting a tangent handle affects only the key of that handle.
Tutorial: Animating a flowing river
The default auto-tangent types create a function curve that has ease-in and ease-out built into the curve. This causes the animation to start slowly, speed up, and then slow to a stop. While this may be a good starting point for many animations, it won't work for those that should have a constant speed. This example shows how to create a river with a material animated to a constant speed.
To create a flowing river, follow these steps:
1. Open the River.max file from the Chap 37 directory on the CD.
This file contains a river surface made from a loft. The V Offset for the River Water material's diffuse channel has been animated to simulate flowing water (yes, this river has a checkered past . . .).
2. Click the Play button.
The river flow starts out slow, speeds up, and then slows to a stop.
Note
The river flows using a checker texture map. Make sure to select a viewport with textures enabled to see the flowing effect. •
3. Open the Track View–Curve Editor, and locate and select the V Offset track for the river's material. (You can find this track under the Scene Materials⇒River Water⇒Maps⇒Diffuse Color: Map #2 (Checker)⇒Coordinates⇒V Offset menu command.)
4. You have two easy options for creating an animation with a constant speed. The first changes the entire controller type; the second changes the individual key's tangent types.
Option 1: Right-click over the V Offset track and choose Assign Controller or choose Assign from Controller on the menu bar to open the Assign Float Controller dialog box. Select Linear Float, and click OK.
or
Option 2: Select both keys by clicking one key, holding down the Ctrl button, and clicking the other, or by dragging an outline around both keys. Click the Set Tangents to Linear button.
Whichever method you use, the line between the two keys is now straight.
5. Click the Play button.
The river now flows at a constant speed.
6. To increase the speed of the flow, select Move Keys Vertical from the Move Keys button flyout, and select and move the end key higher in the graph.
The river flows faster.
Figure 37.16 shows the river as it flows along.
Applying out-of-range, ease, and multiplier curves
Out-of-range curves define what the curve should do when it is beyond the range of specified keys. For example, you could tell the curve to loop or repeat its previous range of keys. To apply these curves, select a track and select the Out-of-Range menu command