【正文】 lt. Anchoring a foot to the ground so it does not move is challenging because whenever you move the body, the feet slide. A hand resting on a desk has the same problem. IK moves the skeleton with goal objects such as a null. Using IK, the task of anchoring feet and hands bees very simple. The disadvantage to IK is that a great amount of control is packed together into the goal objects. Certain poses bee very difficult to achieve. If the upper body does not require any interaction with its environment, then consider a blend of both IK and FK. IK can be set up for the lower half of the body to anchor the feet to the ground, while FK on the upper body allows greater freedom and precision of movements. Every situation involves a different approach. Use your judgment to decide which setup fits the animation most reliably. 11. Add dialogue. It has been said that more than 90% of student animations that are submitted to panies lack dialogue. The few that incorporate speech in their animations make their work highly noticeable. If the animation and dialogue are well done, then those few have a greater advantage than their petition. Companies understand that it takes extra effort and skill to create animation with dialogue. When you plan your story, think about creating interaction between characters not only on a physical level but through dialogue as well. There are several techniques, discussed in this chapter, that can be used to make dialogue manageable. 12. Use the graph editor to clean up your animations. The graph editor is a useful tool that all 3D animators should bee familiar with. It is basically a representation of all the objects, lights, and cameras in your scene. It keeps track of all their activities and properties. A good use of the graph editor is to clean up morph targets after animating facial expressions. If the default ining curve in your graph editor is set to arcs rather than straight lines, you will most likely find that sometimes splines in the graph editor will curve below a value of zero. This can yield some unpredictable results. The facial morph targets begin to take on negative values that lead to undesirable facial expressions. Whenever you see a curve bend below a value of zero, select the first keyframe point to the right of the arc and set its curve to linear. A more detailed discussion of the graph editor will be found in a later part of this chapter. ANIMATING IN STAGES All the various ponents that can be moved on a human model often bee confusing if you try to change them at the same time. The performance quickly deteriorates into a mechanical routine if you try to alter all these parts at the same keyframes. Remember, you are trying to create human 計(jì)算機(jī)與信息學(xué)院 本科畢業(yè)設(shè) 計(jì)（論文） 14 qualities, not robotic ones. Isolating areas to be moved means that you can look for the parts of the body that have motion over time and concentrate on just a few of those. For example, the first thing you can move is the body and legs. When you are done moving them around over the entire timeline, then try rotating the spine. You might do this by moving individual spine bones or using an inverse kinematics chain. Now that you have the body moving around and bending, concentrate on the arms. If you are not using an IK chain to move the arms, hands, and fingers, then rotate the bones for the upper and lower arm. Do not fet the wrist. Finger movements can be animated as one of the last parts. Facial expressions can also be animated last. Example movies showing the same character animated in stages can be viewed on the CDROM as CD111 AnimationStagesMovies. Some sample images from the animations can also be seen in Figure 111. The first movie shows movement only in the body and legs. During the second stage, the spine and head were animated. The third time, the arms were moved. Finally, in the fourth and final stage, facial expressions and finger movements were added. Animating in successive passes should simplify the process. Some final stages would be used to clean up or edit the animation. Sometimes the animation switches from one part of the body leading to another. For example, somewhere during the middle of an animation the upper body begins to lead the lower one. In a case like this, you would then switch from animating the lower body first to moving the upper part before the lower one. The order in which one animates can be a matter of personal choice. Some people may prefer to do facial animation first or perhaps they like to move the arms before anything else. Following is a summary of how someone might animate a human. 1. First pass: Move the body and legs. 計(jì)算機(jī)與信息學(xué)院