Squash and Stretch Revisited

Process
In this lab, we are basically required to add squash and stretch to our bouncing ball to enhance its bounciness.

However, because this tutorial did a different way of creating the bouncing ball, I have decided to follow the tutorial instead. Those obvious differences between my method and the tutorial's method include:

• Group the ball into itself two times, one for translation and one for rotation. Not sure why this is needed. I found one of the possible reasons inside the Maya F1 help, but couldn't be sure whether they are talking about the same thing: 

"It is generally a recommended practice to animate a parent (group) node rather than objects themselves. By animating a parent node, you can avoid problems that occur when the animation of one object in a hierarchy conflicts with the animation in another part of the hierarchy." - Maya's Animation Help Tutorial.

• Created a deformer before we start the animation process. Obviously this wasn't needed in the previous lab.
• Locking some attributes. Since now we have special groups for a particular group of attributes, we don't want to accidentally change translation values for rotation attributes.

The factor for the deformer was used to change the shape of the form. A positive value will gives a stretched ball (the shape when it bounces off), while a negative value gives a squashed ball (the shape when it hits the ground).

Just like the translate attributes, rotation attributes and etc, the factor attribute for the deformer can be key-framed and given different values for different frames, so that it can be changed throughout the animation.

How big should the values be will depend on how much exaggeration we want. The bigger the (absolute) value, the more deformed and stretched/squashed it is, thus being more exaggerated. Smaller value means that there will be less stretch and squash, which results in less exaggeration but also might be hard to see. You won't use smaller values if the thing is bouncy though.

The graph below shows the change in the factor value for our deformer for both objects that we need to animate: the tennis ball and the beach ball.

And... yet another video of my final animation after all the work done!

Reflection
In my opinion, it is still very difficult to get my squash and stretch correct. Sometimes I switch the values back and forth, from big values, to small values, and back to big. Real-life footage seems to have little use in here since they do not seems to squash and stretch much (either that or the quality of the video footage is too poor to reflect that?) Perhaps I can use cartoons instead as references for animations such as this.

The deformer was very useful because it allows us to change the shape of the ball without needing to use the Scale tool. The reason being that the squash and stretch principle states that objects may change shape, but their volume should remain the same. With the deformer, you can change the shape without screwing up the overall volume. Using the Scale tool is risky and you might end up getting a bigger ball than original.