Master Disney’s 12 classic principles of animation in 3D with Steve Lambert’s regular series of articles on the fundamentals of CG. This week: arcs
This week Weta Digital’s animation director Steve Lambert continues his series on Disney’s 12 classic animation principles as he explains how to capture the sweeping movements of natural forms. (To find previous topics scroll to the bottom of this post.)
FOR: Any software | TIME TAKEN: 4 hours | TOPICS COVERED: Arcs | ALSO REQUIRED: Maya (to view scene files)
Download the project and animation files for this training:
fundamentals_7.zip (13.2MB)
In nature, the structure of most vertebrates and the connection of their limbs causes movements to form arcs of one sort or another.
Any movement, simple or complex, is a series of rotating and counter-rotating arcs. But more importantly, arcs are gestures or lines of action; they are what give your animation consistency and flow, whereas straight lines give power and emphasis.
Staging is an important aspect of arcs: because the final rendered frame lies on a 2D plane, the importance and emphasis of your arcs should be biased toward the camera view.
In other words, the arc that is viewed from the camera is more important than any arcs formed in 3D space.
There are several ways to visualise your arcs as you work.
You could sketch thumbnails of your sequence out first (a good idea in any circumstance) and draw your arcs in.
You could sketch your curves with a curve tool: the one I mostly use in Maya is Animation menu set > Animate > Create Motion Trail (with Draw style set to Line in the options). It gives you a constantly updating line, so you can see your arcs as they take shape.
One method I personally don’t recommend is drawing lines directly on your monitor – even with a whiteboard marker!
It’s been said that computers make this principle hard to apply, but I disagree. The nature of joints in 3D means that arcs are as inevitable and natural as they are in the real world – as opposed to the lack of a physical skeleton in 2D animation, for example.
You still have to control gestural arcs, but the danger of limbs growing and shrinking mid-shot is pretty slim.
A big exception comes when you are using IK to control your movements: you have to be careful how your arcs are forming, and they generally require more keyframes to achieve the desired results.
In the example videos for this issue, I’ve specifically used IK for the main ‘action’ arm to help illustrate the concept. The main point that I’m tracing is the tip of the ping pong paddle.
Arcs_01.mov shows most of the action in place.
If you look at the arcs in Arcs_02.mov, however, the lines are messy and the flow from one swing to another is broken. Because the IK handle is basically moving in world space, it doesn’t inherit any motions or arcs of the body. You need to add all of that in, as well as forming the action to suit the camera.
Arcs_03.mov and Arcs_04.mov show the result.
The arcs are much smoother: not only do they stop the arm slicing through the torso, but the readability of the action is much better. This is especially important with action that comes toward the camera.
Watching your arcs isn’t limited to large limb movements. Subtle movements are just as important; the rolling motion of the hips, the rise and fall of the head in a walk, the sweep of a head turning… even the movement of your eyes.
Arcs add clarity to your action, and make a drastic difference to the quality and appeal of your animation.
To see the examples of these animation principles in action download the fundamentals_7.zip
Next week we’ll show you how to add secondary action to your animation.
Tutorial credits
This tutorial uses the ‘Andy’ rig created by John Doublestein for the Savannah College of Art and Design.
(This article was first published in issue 123 of 3D World, December 2009.)
About the author
Steve Lambert has been working in the CG industry since 2001. Currently director of animation at Weta Workshop in New Zealand, his recent feature film work includes Prince Caspian and Avatar
scoobasteve.co.nz
Posted on Monday, June 25th, 2012 at 3:33 pm under Guides, Tutorials. You can subscribe to comments. You can leave a comment, or trackback from your own site.
Tags: 3D basics, 3D training, animation tips, arcs, CG principles, cushioning, Disney’s 12 classic principles of animation, free, Free 3D training, Steve Lambert
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