Rigging and Anatomy
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If everything looks good with the rig, you can finally begin weighting. Weighting is the process of assigning a value between 0 and 1 for each vertice of your model to each joint in your skeleton. A vertice can only have a total weight of 1, so it must be distributed among the joints. For example, the skin on your character's forearm would be weighted to both the joint for the wrist and the joint for the elbow. It is this detailed network of “weights” that actually lets your skin move with the joints. Weighting your character can be a tedious process. It is important though, and if not done carefully it can make a great model look bad. Anatomy also plays an important role when weighting.
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| The rig in action (left) and with muscles added (right). Click for larger view. | |
Just like the skeleton in your body, the skeleton in your character will be the driving force moving it around. Take a look at your arm for a second. Extend your arm straight out in front of you, now twist your wrist around both ways as far as you can. Notice the skin of your forearm sliding over the muscles. This is a good example of how when bones move, the skin should follow accordingly. Your key to getting this look is with weighting. To account for the muscles you'll need something more though.
You have probably heard about some of the advanced muscle system techniques being used at larger studios these days. Some go as far as to model the entire skeletal and muscular systems for each character and create a dynamic system that moves the skin on top of it. Not everyone has access to all the cool plugins and scripts that the bigger studios have. Chances are you don't have an entire team of people working on it either. So how do you include muscles in your character then?
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Depending on the program you are using, there is usually some kind of "flexor" or "influence" object you can add to affect the skin. Using scripting, expressions, or by keying movements, you can quickly create your own muscle movements on your character. I only mention a few, but there are countless ways for you to add in muscles to your skeleton. Do some research into the software you’re using to see what other people are trying.
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| Incorporating a muscle system of some kind into your character while rigging is a good idea. Click images for larger view. | ||
It is subtleties like muscle movement that can really bring life to your character. Other things to consider are fat jiggling and tendons sliding underneath the skin. While you probably aren't going to have time to include all of this, you should at least understand why you would need it. Try to dedicate a certain amount of your time while rigging to looking into adding a muscle system of some kind into your character. Even if you don't get it exactly right, it will probably still turn out better than if you depend solely on weighting for your deformations.
If you do everything according to anatomy, your audience should be able to look at your character and believe his movements. When Jurassic Park came out 10 years ago, no one questioned the rampaging T-Rex running like a giant chicken towards the jeep trying to catch a free meal. Why is that? Because it just looked right. The muscles, the skin, the mouth, the eyes, everything was moving exactly as you would imagine it should. We bought it.
Even with all the vast improvements in technology, people are still able to pick out CG in movies if it doesn't look right. You just know when something doesn't look right, it's human nature. This is why anatomy plays such an important role when you're trying to bring a character to life. If it doesn't move like it should, then who will believe it?
With an understanding of anatomy and movement, you should be well on your way to making accurate rigs for your characters. Whether you're new to rigging, or are a seasoned pro, anatomy should be an important factor in your production process. When you take your time and really apply yourself to it, you'll be surprised at the results. All it takes is a little patience. You'll find you're looking at the world through different eyes, analyzing how everything is moving, and paying careful attention to the details. It's not just a frog hopping to the next stone anymore. It's now a chain reaction of bones, muscles, and skin all acting together as a single energy to take him where he wants to be. It's signs like this that indicate you just might be a TD at heart.
Joe Harkins is currently a "puppeteer," aka Creature TD, at Tippett Studio, in Berkeley, CA, working on The Matrix Revolutions and other film projects full time. His background is in character setup and animation for commercials and film.
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