11/20/09

Walk Cycle - Meet Norman

I'm getting a bit of a head start on the next week's assignment so I can enjoy the Thanksgiving Holiday. This is the start of a three-week long assignment with a few milestones to show along the way.

We are now delving into a walk cycle with a 3D character. Essentially, the same principles apply as the 2D walk cycle with contact points, passthrough points, and weight points... except this is in full 3D! There are a few more things to check out and make sure they work. First things first, we were given Norman, a fully rigged model to work with:

Looks frightening to work with, doesn't it? Are you confused yet? Well, I'll help you out. All of the little shapes in space are controllers that help one move and manipulate Norman's body. They are all set up in a way that they are relative to one large control, that way if you need to move the character in the scene, you don't have to start all over again. (As a side note, rigging is one of the things I am going to school to learn along with modeling and texturing.)

Norman's limbs are set up in two different rigging styles: Forward kinematics and inverse kinematics. There are various advantages to both, but in this example his arms are set up as forward kinematics while his legs are set up as inverse kinematics. Forward kinematics means that you animate from the body outward. For example, if I wanted to move his arm, I would first animate the shoulder, then the elbow, then the wrist. Inverse kinematics is set up just the opposite so that you animate from the extremities inward. So if I wanted to move his legs, I would move his foot and the computer would interpolate where his calf, knee, and thigh would go.

So, where do we start? Well, the first place that major movements usually come from is the hips. which is the root controller for the entire character rig. It moves up and down and slightly front to back as one walks. It also pivots a little bit as well. One the base motion of the hips is figured out, then you start working on the legs, keeping in mind the same principles as a 2D cycle. After the feet pivot and move correctly, the next part is the front and back motion of the spine. After all, your spine is continually absorbing the shock of walking and therefore springs back a bit. After all that, you get something that looks like this:

video

Looks good from this view, but what about the front? As a person walks, their hips shift up and down depending on which leg is bearing the weight. In addition, the shoulders counteract the movement of the hips:

video

Voila! The legs and torso are animated. Now you can take a look at how it is in full perspective:

video

This is a complicated process but it is fun to see the end result. That's it for this week. Next time, the arms start swinging.

No comments: