Bouncing Balls (BB)

This assignment will account for 30% of your final grade. Hand-in will be due at the end of class 5

Physics of Bouncing Balls. (BB) Modules 2-5. Animate 3 Balls of equal size but different properties: a springy rubber ball, a bowling ball and a very light beach ball or balloon. Play-blast from an orthographic side view so that all the balls can be clearly seen. Look for opportunities to have them bounce from different heights and deflect against different surface angles. The balls do not need to interact with each other and they do not need to come to a stop by the end of the scene. Featured principles: Timing, Arcs, Slow In/Out, and Squash/Stretch. 6 sec. long (180fr)

What I'll be grading on this assignment:
  1. Do the bouncing balls consistently convey their individual properties?
  2. Are the arcs of the bounces parabolas with the apex at the proper location?
  3. Does the Squash and Stretch follow the tangent of travel of the ball?
  4. Do you meet all the required parameters of the assignment?
  5. Are you effectively using the principles of Timing, Ease In/Out, Arcs, and Squash & Stretch?

Module 1 - Timing, Arcs and Ease In/Out

We've talked about the relationship between distance, speed and time. Because these balls are the same size, we can only distinguish their different material properties with timing and ease in/out. Squash and stretch will also play a role, in the next module.

First (as always) we start with planning. A few quick and simple drawings to show your environment that you want to use, with some lines showing the path each ball with take. Be sure to account for any potential interactions with the environment or the other balls in the scene. The important notion here is to plan in a way that allows you to make mistakes quickly, so that we can get the bad ideas out of the way. Work out the choreography so that you have an idea you're happy with. Make note of the order that things happen in (which may require a few sketches.) Here's and example of a simple plan for this assignment. I've written a few notes and reminders for myself when I get into the animation. (*NOTE: This is just an example plan. You don't have to follow the same plan or criteria I have listed here. Come up with a plan of your own.*)

I realized this plan has some flaws (I underlined them in red). At least with sketches, it's very fast and easy to make mistakes. Looks like I need a new plan if I'm going to meet all of my criteria. Back to the drawing board.
This plan is a bit better - I've also noted along the green ball path when other balls start moving. It would take a lot longer to work out these issues if I just dove headfirst into Maya and started animating without a plan. These doodles took me about 15 minutes to make. Yay planning!


Here's the first pass with just the arcs and timing worked out. Each ball should have a distinctly different sense of mass and material.

Module 2 - Refine Your Work then Add Squash and Stretch

After review in class, you should have a better idea where you can improve on your work.

Some Common Errors to Watch For:

  • Hide controllers when play-blasting.
  • Arcs are asymmetric/not a smooth parabola.
  • Timing issue, accelerating or decelerating at wrong time.
  • Timing issue, moving too fast.
  • Timing issue, moving too slow.
  • Not enough Ease In/Out.
  • Weight/physical properties inconstant.
  • Not enough acceleration at bottoms of arc - timing too floaty.
  • Too fast at bottom of arc, causes "strobing".
  • Bouncy ball sticks too much at bottom of bounce.

Once you've corrected any issues with your core animation, we can add squash and stretch to your bouncy rubber ball. See the picture below for guidance:



Note that the ball doesn't squash at the apex of the bounce (or it would look like jello). Also take note that the biggest stretch pose is immediately before and after the squash. Don't forget that the long axis of the stretch is along the path of the ball, essentially pointing in the direction of travel.

Here's my second pass with squash and stretch added to the bouncy rubber ball (and a bit to the beach ball.) The heavy ball does not deform, to support the idea it is rigid and hard.


Module 3 - Polishing

Based on review in class, make any fixes needed to ensure your work is the best quality you can achieve. Review the list at the top of this page "What I'll be grading on this assignment". Your priority should be to have all those items working well.

Hand-in on this assignment is at the end of week 5