A pose is simply the way a character presents itself to the camera. If the character is sad, happy, frightened or brave, you should be able to read that emotion in its pose--the way the character stands, where its hands are placed, the position of its head. Every part of the body has a role in creating the pose. Theater, dance, mime, and countless other performing arts involve posing to a great extent. Similarly, animation is another art form that relies heavily on clear poses and silhouettes to convey a message.
When animated, your characters need to show emotion. Even the simplest shots require a character to hit a strong pose. Whether the character is sad, happy, proud, or surprised, the emotion shows in the body and the pose (see Figure 1).
Figure 1 A simple character can show a great deal of emotion simply through the pose of the body.
Animating with Poses
In the golden age of animation, animators discovered there are two basic methods for animating a scene: straight-ahead and pose-to-pose. Each method uses posing differently and has its own place and its own advantages.
Pose-to-pose animation is the more controlled of the two. In this method, you plan your shot and get the main poses of the character within the shot blocked out. If your character is standing up from a chair, for example, the poses may be leaning back, grabbing the armrest for support, leaning forward, and, finally, standing up. A character winning the lottery may read the lottery ticket and then show disbelief, shock, and joy. The theory is that every action can be broken down into a series of distinct poses. From there, it's a matter of creating in-betweens or letting the computer in-between the poses for you--and, of course, tweaking these as necessary. It is a good way to animate difficult and tightly choreographed shots, as well as slower subtle pantomime moves, because those do not have many surprises or quick motions to them. Pose-to-pose animation is also good for dialogue, because each pose can be fit to the major points in the dialogue track. The downfall of the method is that it may lack spontaneity.
Straight-ahead animation is pretty much what the name implies. In this method, you start on frame one and animate "straight ahead" from there. This method is more improvisational in nature and can sometimes lead to very spontaneous and complex motion. It's also a great method for quicker action motions because of the spontaneity. Straight-ahead is the method closest to "acting" a frame at a time, and it is very similar to the techniques used in stop-motion animation. If you are trying to achieve a stop-motion look and feel to your animation, this is certainly the way to go. Still, this method can make it hard to achieve well-defined and solid poses, sometimes making animation that is hard to "read." It also makes animating complex shots difficult.
Combining the Two Methods
You can, however, combine the two methods and get the best of both. Computer animation gives you the bonus of being able to do this rather easily. Most fast machines can play back an animation test almost instantly. This makes it easy for the animator to block out a series of poses rather quickly, almost in a straight-ahead fashion, or animate a frame at a time in those sections that might need more spontaneity.
The question that still remains, however, is one of thought process. How do you approach animating your scene? Do you plan your shot carefully (pose-to-pose) or do you improvise (straight-ahead)? This is not an easy question to answer, and the best advice is to use your intuition and experience. Overplanning a shot may very well sap the life out of it. Being more improvisational can add unexpected touches and details you would have never dreamed of. On the other hand, complex shots need to be planned very carefully or all the elements simply won't sync up.
When you combine the two methods, you plan the extreme poses and then tighten that up with straight-ahead interpretation between those poses. The first part lays the groundwork, and the second part spices it up and gives it life, leaving behind all the computer interpolation that makes an animation look mechanical. With a computer, you can easily use both. I highly recommend you use both techniques to get a good animation; if you rely on just one or the other, you easily see where their weaknesses are.