I had to animate a ball bouncing in one of my shots at work this week and it gave me the idea of writing a post on the topic. I think the bouncing ball is the foundation of animation and is absolutely worth spending time to get it down to perfection. Just browsing through the Class 1 Assignments on A.M, I can see a lot of people can pull it off, but for those who haven’t quite got the hang of it I tend to think there are 2 areas where they trip up: planning and understanding how the graph editor relates to the viewport.
If we can’t demonstrate with pencil and paper the arc, spacing and timing, we’re never magically going to get it right in Maya. Take the time to check out the Survival Kit on how a ball bounces and then draw it yourself with all the information.
This is not enough:
I noticed a lot of people show planning like this. While it shows arcs and the fall off in height, it misses spacing and timing. Spacing is key in a ball bounce. Just simple ticks is enough to show the idea that a ball doesn’t have even spacing.
That’s all it takes. It’s not perfect, it’s rough planning but it clearly shows the concepts and gives us time to figure out how things should move before adding all the complexities of working in Maya.
Assuming the above planning is for a basketball, there are also two points to clarify:
1. What is the drop off rate on the bounce height for a basketball? Successive bounces are usually lower by the same percentage, different balls with different weights will have different percentages.
2. How long does a bounce take? Shoot or get some reference and count the frames (if it’s at 24fps). How long is the first bounce, then the second, the third, etc.
Mark both down on the planning sketches. Basketballs take a long time to come to rest, when animating one we’re not going to be aiming for real life precision. We’ll be able to get something more believable though having that information as a starting point.
Graph Editor vs Viewport.
The graph editor takes getting used to, but trial and error will get us a long way. One easier way to get a grasp of it is by having more visual feedback of what the animation is looking like and how changes in the graph editor are affecting it. I’ll point out 3 ways of doing this:
1. Arc Tracking.
In this case I’ve laid down 3 keys and animated a quick bounce just as an example. Now if we turn on Motion Trails within Maya we can see the arc the ball is moving on. To do so, make sure we are in the Animation menu bar (hit F2), select the ball, then go to Animate > Create Editable Motion Trail
What we also would like to see is a representation of the position of the ball on each frame. To do that we can select the curve and in the Attribute Editor turn on Show Frame Markers. Now we can see our arc and our spacing.
Notice how our visual feedback in Maya is looking a lot like how we drew our planning ; ) To delete the motion trail, just select it and press delete.
Another way of visually seeing more of your animation is by using ghosting.
In this case Maya will show where your object will be in the frames following and preceding the current frame. To turn this function on, select your ball, go to Animate > Ghost Selected
I prefer to turn the options on and choose Custom Frame Steps. In this way I can choose the number of frames to show before and after the current frame.
To turn ghosting off, simply go to Animate > Unghost All
3. Screen Drawing.
The last way is to literally draw on your screen. There are two ways, find a screen drawing application or use an erasable whiteboard marker. Screen drawing software ranges from free to about $20 (I will say without hesitation $20 is definitely worth it). At work we can’t just install our own apps, so a lot of animators will have a piece of perspex they put over their screen and then draw on it with a white board marker.
While more time intensive the advantage of this method is I can draw the arc from my current animation and also I can also draw the arc I intend the ball to take. Motion Trails and Ghosting are only able to show what your animation is currently doing, while drawing on your screen gives you the advantage of being able to draw the arcs, spacing, keys, poses, etc that you want to achieve. It can act as a guide as much as it can as visual feedback.
I hope that helps in some ways. To recap: don’t skimp on planning. Planning = getting the concepts figured out before adding the complexities of Maya. And secondly, use some way of visually seeing your arcs+spacing to gain a better sense of how changes in the graph editor will impact the animation.