How to Animate Complex Character Interaction

“So how do you handle a scene with two or more characters interacting?
Specifically, how would you handle physical fighting or wrestling?”

Once again, it comes down to the 4 main stages of any animation:

  1. Foundation
  2. Structure
  3. Details
  4. Polish

Lets look at these and how they specifically apply to complex character interactions.

Stage 1. Foundation

Before you ever start posing or setting keys, you must have a solid plan.

You will need to know the choreography of the fight. When do the characters come into contact with one another? Where is the driving force coming from on each contact?

Really, the fastest way to plan such a scene is to film a few people acting it out. It will take much longer if you just sit down and try to thumbnail it out without any Video reference.
With live actors, you can direct them in real time and experiment with different ideas.

Once you’ve filmed your Video reference, go through and sketch out every key pose.

  • Look for changes of direction in weight or poses
  • Look for contact and transfer of force between your characters.

Make sure you have all of these sketched out with a note of the timing according to your reference.

Now you’re ready for…

Stage 2. Structure

Set all of your key poses on your characters in 3d.

Many animators like to use Stepped keys, but some software packages don’t allow stepped keys.
At least try to use linear.

Make sure you get all points of contact keyed in on all of your characters.

Check all of your key poses from every angle to ensure they contain proper weight, balance and force.

Stage 3. Details

Here we can begin to smooth out our animation and add in breakdowns and inbetweens, but don’t
start offsetting keys and try to resist the urge to start really polishing.

A great way for getting the contact between two characters to stick – is to link a null or a dummy to the point of contact, then align the end effector of the other characters limb to that dummy on every key frame.

Make sure you have your weight and force worked out before you do this, that way you know which character or limb is leading the motion.

Stage 4. Polish

Now you can go to town and really polish your animation.

Go through it many times, each time focusing on one of the 12 principles of animation.

Perfect every arc on your pelvis, hands/arms, head/eyes and any other main moving object.

Make sure that the ease in/out of every key is what YOU want, not what the computer has given you.

Make sure you have overlap and follow through so that everything doesn’t come to a stop all at once in any part of your scene.

Ok, that’s a very simplified breakdown of how to approach a complex interaction scene, but really, you’re not going to learn much from reading emails. Get outta here and go try it!


Should I Use IK or FK?

Ah, the age old question: IK, or not IK…

Really, these days this question is almost obsolete. No matter what program you use for animation, it most likely has a switchable IK/FK solution.

Personally, I wouldn’t animate and character without one anymore. B)

It’s important to understand what is happening to your characters joints at all times, though. The problem with IK is that it allows animators to become lazy. There, I said it.

You see it all the time in reels and newbie animation.

Heck, we all do it sometimes. When we let the computer worry about where the elbow (or knee, or spine, or tentacle joint) is, we can easily get lazy. This is the path to average character animation (at best).The important thing is arcs and force, not just in your end effector or hand, but also in the hinge joint, or elbow. Do both express an arc that shows the mood and attitude that you want for this particular movement? Your character is more than just their end effectors, and being a good character animator means maintaining control of every aspect of your scene.

Is it the rigging of your character, or the ik of real creatures?

The “IK Lock” that so many animators try to avoid is quite present in everyday motion. An extreme example is a boxer throwing a punch: his arm (or her arm if you’re in my family) snaps to full extension and then jerks back to slightly bent. Yet this same thing occurs in less extreme cases such as:

  • Rasing your hand quickly to answer a question
  • The extension of a leg just before contact while walking
  • Running
  • Jumping
  • Any movement where you fully extend a limb!

I personally find IK is the best system for mimicking this type of motion on my characters. These days, I rarely use FK limbs in my animation, unless I am having real trouble with my arcs or poses.

I find IK allows me to pose faster and thus try out more poses, ultimately leading to better animation. It also allows me to place the limb exactly where I want it.

As long as I don’t get lazy and just let the animation software sort it out for me, I’m quite fine using pure IK limbs.

So really, in your animation, whether you use IK or FK on your characters should be your choice. However, as animators, we often must work with the tools we are given. If you are asked to animate a character that ONLY have IK arms or only FK legs, you should do your best animation with whatever you are given.


Why not practice animating both? Why not build a simple arm rig right now, and make two copies of it: one FK and one IK.

Then practice animating both and getting the same results. Try animating many different types of motion, and see what it is you have to do to get the same animation our of BOTH rigs!

It’s by doing little animation exercises like this that will really boost your skills as a character animator.

So get out there and Start Animating!