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Lecture 8: Adding Squash and Stretch

Page 1.

E-mail Billy.

You may have noticed that your bouncing ball animation didn't look quite as real as mine. That's because mine had some added Squash and Stretch.

See the lecture on "The 12 Principles" in the course documents folder for more information on squash and stretch.

Basically, squash and stretch are used to show the density or rigidity of an object. Ask yourself: Is this object completely rigid, or will it give if I apply some pressure to it? 

Another use for squash and stretch is that they can bring to life otherwise inanimate objects. A toaster, for example, is a rigid object, but by applying the right amount of squash and stretch, we could make it come to life and bounce across the table!

• You should have a few animated balls with at least one using the correct tangent types. (see lecture 7 - page 3).

• Delete all the balls except the one bouncing correctly.

• Zoom Extents all.

• In the Top View, zoom out slightly, and then create a box to act as a table for the ball to bounce on. The height of the box is not really important.

• Now, to add squash and stretch, were going to use scale tools, so the first thing were going to do is create four scale key frames, one at the beginning and one at the end of the animation, and one just before and after our squash. These are to preserve the round shape of the ball at the top of it's bounce.

• Up until now, to create key frames we have had to change parameters, but in this instance, we don't want to change any parameters, we want to preserve them. In order to create a key frame without changing anything, we can do the following:

• Command Panel>Motion Panel>PRS Parameters Rollout>Create Key

• With the time slider at frame 0, click on Scale under Create Key. This records our sphere's Scale parameters at frame 0 and generates a Scale Key frame. 

• Do the same thing at frames 30, 13 and 17.

• Now choose the Select and Squash Tool:

Although in real life a ball wouldn't squash until it actually hit the ground, in animation, it seems to look just as realistic if you add the same amount of squash either side of the bounce, which is what were gonna do!

• Move the time slider to frame 15

• Select the Front View

• Constrain the Axis to Y

• Turn on the Animate button.

• Squash your ball about hmmmmm... this much:

• Right, well that's all the key frames we need, as Max will do all the rest for us through interpolation. But No! When we play the animation it goes horribly wrong!

• So, what could be causing the interpolation between your key frames to be going so weird?

• Think about it, we want our squashing to interpolate directly from one key to the next. One might even say we want it to interpolate in a Linear fashion.

• Save your project now, and then try to sort out this problem yourselves. If you can't figure it out, revert to the saved project and go to the next page.