How Do You Improve the Arcs in Animation?

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FIRST THINGS FIRST:
Before you go crazy improving any arcs, you must know that you need to work from the root of your character outward (pelvis » spine » neck » head). A slight change in the arc of the root may result in a big change in the arc of your wrist.

There are may ways of improving your arcs so I’ve broken it down to a few sections.

DESIGN:
The beauty of animation is you are the one in control, so why not take control over your arcs. They don’t always have to be your standard arc. Different arcs can have different feelings. So here are some things I like to think about when designing my arcs.


* Arcs should not all be the same. Think of different patterns and how they relate to each other. For instance, if you moved through a squiggly arc and then into a smooth arc, you animation may start off feeling chaotic and then end feeling calm or fluid.

* Like any design, angular shapes and patterns have a rough, rigid and maybe even a negative feeling as apposed to a smooth shapes and patterns may have more of a fluid, organic or positive feeling.

* There needs to be at least three frames (3 points) to describe any curve.

* Arcs can have a thickness to them as well. For example if you move your hand through and arc and your fingers are spread wide at the beginning and in the end, but are close together in the middle that arc will have a feeling of going from thick to thin to thick. When doing this its important to remember volume and anatomy.


DRAWING YOUR ARC:
When I think I have an idea for my arc, I plot it out on my monitor with a dry erase marker (for flat panels I may use a sheet of acetate over the monitor). I first plot out my start and end points so I know roughly how much space I’m dealing with and then I draw my arc connecting the two.

Remember, the more detailed your arc is the more frames you will need. For example, if you wish for your object to follow along an “S” curve you will need enough points to keep it from looking like a “Z” curve.

SPACING:
I think the thing most often forgotten when it comes to arcs is the spacing along the arcs. It's not good enough just to make sure that every frame follows the arc, but the spacing along that arc has just as much value. If the spacing is done incorrectly your arc may or may not read.

As a starting point, I think of my spacing along an arc like the coils in a slinky. If you were to stretch out a slinky along an arc, the coils would be closer to each other at the ends and furthest apart in the middle. When you move through the slinky from the start toward the middle, each coil (spacing) gradually gets further and further apart until it reaches its furthest spacing in the middle. From that point, the coils (spacing) get closer and closer together. Like I said, this is just a starting point, your typical arcs ease out, and moves through a breakdown to an ease in type of spacing. Quite often I will see two random coils in the middle of an arc very close together unintentionally, and even though the object is moving through an arc it still appears to pop because the frames before and after don’t lend itself to that spacing.

DRAG, SQUETCH (Squash and Stretch):
When moving through an arc it's important that any drag, or squetching we do follows that path of action as well. For example, in your standard bouncing test, as a ball stretches on its descent the line of action of that ball points back up the arc where it came from.

MOTION BLUR:
This may be a bit unnecessary to talk about and may even complicate things a bit, but when you get to that big studio it matters. Motion blur is like 5-year-old playing connect the dots. It will only draw a straight line from point to point. It doesn’t know to arc in between the dots. So this may or may not be another factor to the design and detail of your arc.


by Nick Bruno
AnimationMentor.com Mentor
Senior Animator at Blue Sky Studios



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