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.
Guest Blogger Nick Bruno
5 comments:
I always thought of arcs as just semi circles and was confused when there would be an animation with a chaotic movement and people would say, "look at those arcs".
This post helped me clear that up, the slinky analogy helps a lot also, fantastic stuff, thank you.
There's a tool that I use at times which I find helps quite a bit. Basically you select the control for the element you want to trace the arcs for, and Maya creates a nurbs curve along the path for the specified time frame. It also adds locators (or spheres) to the path for each frame so you can visualize the timing.
If you turn on Autokey then it also adjusts the arcs as you make changes. Not something you want to use for all occasions, as you can get too mired in the tool, but a great tool if used properly.
It's the cMotionTrailUI tool at the bottom of this page.
Hi!
Great tips there thx!
I have a question about curves and keys. I was told it was better to put keys as less as possible. For exemple, if you make the arm doing an arc, like you said you need at least 3 points. But sometimes computer doesn't act like we want, to we have to correct the movement by adding more and more keys, but we can also play with the curves and bezier. Do you find it's okay to put as much as keys we need? Even if it's a key on everyframe? Or is it better to play a long time with the curves until we obtain de movement we want?
I've been told to keep my curves and keys as clean as possible, but someone else told me also to put keys everywhere to get what I want... I don't know what's better...
Hey Grejotte!
Good question. Ultimately YOU have to do things how YOU feel comfortable. Both methods work and they both have their +'s and -'s.
You have to find what works for you in your situation. keep in mind it might change each time.
Animation is the type of medium where rules and ways of doing things are constantly broken or altered.
Either way, there is NO rule that says use less keys.
Thx Nick!
Now I feel better and more free hehe.
But I was wondering too if there was a better method knowing thay other people might sometimes re-work on my animations... (we're working on a tv show) so it might be too confusing for them if I put keys everywhere, but at the same time, it might keep me from doing a best animation.
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