计算机与信息学院 本科毕业设计（论文） 外文资料翻译—原文部分Fundamentals of Human Animation(From Peter Ratner.3D Human Modeling and Animation[M].America:Wiley,2003:243~249)If you are reading this part, then you have most likely finished building your human character, created textures for it, set up its skeleton, made morph targets for facial expressions, and arranged lights around the model. You have then arrived at perhaps the most exciting part of 3-D design, which is animating a character. Up to now the work has been somewhat creative, sometimes tedious, and often difficult.It is very gratifying when all your previous efforts start to pay off as you enliven your character. When animating, there is a creative flow that increases gradually over time. You are now at the phase where you become both the actor and the director of a movie or play.Although animation appears to be a more spontaneous act, it is nevertheless just as challenging, if not more so, than all the previous steps that led up to it. Your animations will look pitiful if you do not understand some basic fundamentals and principles. The following pointers are meant to give you some direction. Feel free to experiment with them. Bend and break the rules whenever you think it will improve the animation.SOME ANIMATION POINTERS1. Try isolating parts. Sometimes this is referred to as animating in stages. Rather than trying to move every part of a body at the same time, concentrate on specific areas. Only one section of the body is moved for the duration of the animation. Then returning to the beginning of the timeline, another section is animated. By successively returning to the beginning and animating a different part each time, the entire process is less confusing.2. Put in some lag time. Different parts of the body should not start and stop at the same time. When an arm swings, the lower arm should follow a few frames after that. The hand swings after the lower arm. It is like a chain reaction that works its way through the entire length of the limb.3. Nothing ever comes to a total stop. In life, only machines appear to come to a dead stop. Muscles, tendons, force, and gravity all affect the movement of a human. You can prove this to yourself. Try punching the air with a full extension. Notice that your fist has a bounce at the end. If a part comes to a stop such as a motion hold, keyframe it once and then again after three to eight or more keyframes. Your motion graph will then have a curve between the two identical keyframes. This will make the part appear to bounce rather than come to a dead stop.4. Add facial expressions and finger movements. Your digital human should exhibit signs of life by blinking and breathing. A blink will normally occur every 60 seconds. A typical blink might be as follows:Frame 60: Both eyes are open.Frame 61: The right eye closes halfway.Frame 62: The right eye closes all the way and the left eye closes halfway.Frame 63: The right eye opens halfway and the left eye closes all the way.Frame 64: The right eye opens all the way and left eye opens halfway.Frame 65: The left eye opens all the way. Closing the eyes at slightly different times makes the blink less mechanical.Changing facial expressions could be just using eye movements to indicate thoughts running through your model's head. The hands will appear stiff if you do not add finger movements. Too many students are too lazy to take the time to add facial and hand movements. If you make the extra effort for these details you will find that your animations become much more interesting.5. What is not seen by the camera is unimportant. If an arm goes through a leg but is not seen in the camera view, then do not bother to fix it. If you want a hand to appear close to the body and the camera view makes it seem to be close even though it is not, then why move it any closer? This also applies to sets. There is no need to build an entire house if all the action takes place in the living room. Consider painting backdrops rather than modeling every part of a scene.6. Use a minimum amount of keyframes. Too many keyframes can make the character appear to move in spastic motions. Sharp, cartoonlike movements are created with closely spaced keyframes. Floaty or soft, languid motions are the result of widely spaced keyframes. An animation will often be a mixture of both. Try to look for ways that will abbreviate the motions. You can retain the essential elements of an animation while reducing the amount of keyframes necessary to create a gesture.7.Anchor a part of the body. Unless your character is in the air, it should have some part of itself locked to the ground. This could be a foot, a hand, or both. Whichever portion is on the ground should be held in the same spot for a number of frames. This prevents unwanted sliding motions. When the model shifts its weight, the foot that touches down becomes locked in place. This is especially true with walking motions.There are a number of ways to lock parts of a model to the ground. One method is to use inverse kinematics. The goal object, which could be a null, automatically locks a foot or hand to the bottom surface. Another method is to manually keyframe the part that needs to be motionless in the same spot. The character or its limbs will have to be moved and rotated, so that foot or hand stays in the same place. If you are using forward kinematics, then this could mean keyframing practically every frame until it is time to unlock that foot or hand.8.A character should exhibit weight. One of the most challenging tasks in 3-D animation is to have a digital actor appear to have weight and mass. You can use several techniques to achieve this. Squash and stretch, or weight and recoil, one of the 12 principles of animation discussed in Chapter 12, is an excellent way to give your character weight.By adding a little bounce to your human, he or she will appear to respond to the force of gravity. For example, if your character jumps up and lands, lift the body up a little after it makes contact. For a heavy character, you can do this several times and have it decrease over time. This will make it seem as if the force of the contact causes the body to vibrate a little.Secondary actions, another one of the 12 principles of animation discussed in Chapter 12, are an important way to show the effects of gravity and mass. Using the previous example of a jumping character, when he or she lands, the belly could bounce up and down, the arms could have some spring to them, the head could tilt forward, and so on.Moving or vibrating the object that comes in contact with the traveling entity is another method for showing the force of mass and gravity. A floor could vibrate or a chair that a person sits in respond to the weight by the seat going down and recovering back up a little. Sometimes an animator will shake the camera to indicate the effects of a force.It is important to take into consideration the size and weight of a character. Heavy objects such as an elephant will spend more time on the ground, while a light character like a rabbit will spend more time in the air. The hopping rabbit hardly shows the effects of gravity and mass.9. Take the time to act out the action. So often, it is too easy to just sit at the computer and try to solve all the problems of animating a human. Put some life into the performance by getting up and acting out the motions. This will make the character's actions more unique and also solve many timing and positioning problems. The best animators are also excellent actors. A mirror is an indispensable tool for the animator. Videotaping yourself can also be a great help.10. Decide whether to use IK, FK, or a blend of both. Forward kinematics and inverse kinematics have their advantages and disadvantages. FK allows full control over the motions of different body parts. A bone can be rotated and moved to the exact degree and location one desires. The disadvantage to using FK is that when your person has to interact within an environment, simple movements become difficult. 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 becomes very simple. The disadvantage to IK is that a great amount of control is packed together into the goal objects. Certain poses become 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 companies 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 competition. Companies understand that it takes extra effort and skill tocreate 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 3-D animators should become 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 incoming 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 STAGESAll the various components that can be moved on a human model often become 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 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 forget 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 CD-ROM as CD11-1 AnimationStagesMovies. Some sample images from the animations can also be seen in Figure 11-1. 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. 2. Second pass: Move or rotate the spinal bones, neck, and head. 3. Third pass: Move or rotate the arms and hands. 4. Fourth pass: Animate the fingers. 5. Fifth pass: Animate the eyes blinking.6. Sixth pass: Animate eye movements.7. Seventh pass: Animate the mouth, eyebrows, nose, jaw, and cheeks (you can break these up into separate passes).Most movement starts at the hips. Athletes often begin with a windup action in the pelvic area that works its way outward to the extreme parts of the body. This whiplike activity can even be observed in just about any mundane act. It is interesting to note that people who study martial arts learn that most of their power comes from the lower torso.Students are often too lazy to make finger movements a part of their animation. There are several methods that can make the process less time consuming.One way is to create morph targets of the finger positions and then use shape shifting to move the various digits. Each finger is positioned in an open and fistlike closed posture. For example, the sections of the index finger are closed, while the others are left in an open, relaxed position for one morph target. The next morph target would have only the ring finger closed while keeping the others open. During the animation, sliders are then used to open and close the fingers and/or thumbs.Another method to create finger movements is to animate them in both closed and open positions and then save the motion files for each digit. Anytime you animate the same character, you can load the motions into your new scene file. It then becomes a simple process of selecting either the closed or the open position for each finger and thumb and keyframing them wherever you desire.DIALOGUEKnowing how to make your humans talk is a crucial part of character animation. Once you add dialogue, you should notice a livelier performance and a greater personality in your character. At first, dialogue may seem too great a challenge to attempt. Actually, if you follow some simple rules, you will find that adding speech to your animations is not as daunting a task as one would think. The following suggestions should help.DIALOGUE ESSENTIALS1. Look in the mirror. Before animating, use a mirror or a reflective surface such as that on a CD to follow lip movements and facial expressions.2. The eyes, mouth, and brows change the most. The parts of the face that contain the greatest amount of muscle groups are the eyes, brows, and mouth. Therefore, these are the areas that change the most when creating expressions.3. The head constantly moves during dialogue. Animate random head movements, no matter how small, during the entire animation. Involuntary motions of the head make a point without having to state it outright. For example, nodding and shaking the head communicate, respectively, positive and negative responses. Leaning the head forward can show anger, while a downward movement communicates sadness. Move the head to accentuate and emphasize certain statements. Listen to the words that are stressed and add extra head movements to them.4. Communicate emotions. There are six recognizable universal emotions: sadness, anger, joy, fear, disgust, and surprise. Other, more ambiguous states are pain, sleepiness, passion, physical exertion, shyness, embarrassment, worry, disdain, sternness, skepticism, laughter, yelling, vanity, impatience, and awe.5. Use phonemes and visemes. Phonemes are the individual sounds we hear in speech. Rather than trying to spell out a word, recreate the word as a phoneme. For example, the word computer is phonetically spelled "cumpewtrr." Visemes are the mouth shapes and tongue positions employed during speech. It helps tremendously to draw a chart that recreates speech as phonemes combined with mouth shapes (visemes) above or below a timeline with the frames marked and the sound and volume indicated.6. Never animate behind the dialogue. It is better to make the mouth shapes one or two frames before the dialogue.7. Don't overstate. Realistic facial movements are fairly limited. The mouth does not open that much when talking.8. Blinking is always a part of facial animation. It occurs about every two seconds. Different emotional states affect the rate of blinking. Nervousness increases the rate of blinking, while anger decreases it.9. Move the eyes. To make the character appear to be alive, be sure to add eye motions. About 80% of the time is spent watching the eyes and mouth, while about 20% is focused on the hands and body.10. Breathing should be a part of facial animation. Opening the mouth and moving the head back slightly will show an intake of air, while flaring the nostrils and having the head nod forward a little can show exhalation. Breathing movements should be very subtle and hardly noticeable... 外文资料翻译—译文部分人体动画基础(引自 Peter Ratner.3D Human Modeling and Animation[M].America:Wiley,2003:243~249)如果你读到了这部分，说明你很可能已构建好了人物角色，为它创建了纹理，建立起了人体骨骼，为面部表情制作了morph修改器并在模型周围安排好了灯光。
接下来就是三维设计中最精彩的部分，即制作角色动画到目前为止有些工作极富创意，有些枯燥乏味，但都困难重重在经过了前期的努力后，角色已显示出了活力，这是非常令人高兴的在制作动画时，创意会随着时间的推移不断涌现现在你既是电影和戏剧的演员又是导演虽然动作是很自然的表演，但它即使不比之前的准备步骤更复杂，也极具挑战如果你不懂一些基础知识和基本原理，制作出的动画会很可笑以下几点为你提供一些指导尽管拿它们做实验只要你认为能改进动画，可随意遵守或打破这些规则动画指南：1. 尝试分离各部分有时指的是分阶段制作动画不要试图同时移动身体的每个部位，应集中精力制作具体部位的动画在动画的持续时间内只移动身体的一部分然后返回时间轴的起始位置，制作另一部分的动画通过不断回到起始位置，每次制作一个不同部位的动画，能使整个过程变得清晰明了2. 添加一些延迟身体的不同部位不应该同时开始和停止动作当胳膊摆动时，下臂应该在其随后摆动几帧在下臂停止摆动后手再摆动整个手臂的活动就像是一边连串的连锁反应3. 任何一个动作都不会戛然而止生活中，只有机器会突然停止肌肉，腱，压力和引力都会影响人体的移动你可以亲自证明这一点用力向前推拳直到完全舒展开手臂。
注意最终你的拳头会回弹一下如果一个部位要停止，例如要保持动作，首先把它设置为关键帧，然后在3到8个或更多关键帧后再设置一次关键帧动作图形会在两个相同的关键帧中间产生一条曲线这会使动作有一个回弹而不是马上停止4. 添加面部表情和手指动作数字人体应当通过眨眼和呼吸来呈现生命的气息通常每隔60秒会眨一下眼睛典型的眨眼应该如下所述：第60帧：两眼都睁开第61帧：右眼半合第62帧：右眼紧闭，左眼半合第63帧：右眼半睁，左眼紧闭第64帧：右眼完全睁开，左眼半睁第65帧：左眼完全睁开在不同时间闭上眼睛会让眨眼显得更为自然面部表情的改变可通过眼睛的转动来表明模型脑海中的想法如果你不添加手指动作，手会显得过于僵硬很多同学懒得花时间去添加面部和手部动作如果你花额外的努力在这些细节上，你的动画会变得更有趣5. 摄像机没有拍到的内容不用关注如果胳膊叉到了腿里但摄像机视图中看不到，就不用费心去更正如果你希望一只手看上去靠近身体并且摄像机视角看上去也是如此，即使实际并不靠近，也没必要再做调整这也适用于布景如果所有的表演都发生在起居室，就没必要建造整幢房子考虑绘制背景而不是做出场景每一部分的模型6. 尽量少使用关键帧。
过多的关键帧会让角色动作看上去有痉挛的感觉剧烈，类似于卡通的动作是使用分布密集的关键帧制作的飘逸或柔和、没精打采的动作是通过分布稀疏的关键帧制作的动画中通常结合使用二者试着寻找可以简化动作的方法你可以在保留动画基本元素的同时减少构成姿势所需的关键帧数量7. 通过锁定位置锚定身体的某个部位除非你的角色在空中，否则它身体的一些部位应该被锁定在地面上可以是一只脚，一只手或二者处于地面的部分应该在好几帧上保持在同一位置这样可阻止不必要的滑动当模型移动重量时，落下的脚被锁定在适当的位置对于行走动作这点特别适用有很多方法将模型的部位锁定在地面上除了直接把一只脚或一只手锁定在地面外，另一种方法是把需要保持在相同位置的部位手动变成关键帧角色或其四肢必须移动或旋转，只有这样，脚可手才能保持在相同位置8. 角色应该显示重量三维动画中最富挑战性的一项任务是让一个数字演员显得拥有重量和质量可以使用几种方法来实现第12章中讨论的动画的12个原理之一的挤压与拉伸（或者重量与反弹）是为角色提供重量的好方法通过为人体添加一些反弹动作，可以展示角色受到重力影响的效果比如，如果角色跳起后落下，脚触地后身体要稍微向上抬一下。
对于一个比较重的角色，可以让这个动作重复几次，一次比一次弱这显示出接触的力量似乎让身体微微有些振动第12章中讨论的动画的12个原理中的另外一个——辅助动作是显示重量和质量效果的一种重要方法就用前面跳跃的角色例子，角色着地时，腹部可以上下颤动，胳膊可以微微弹起，头可以向前倾斜等移动与正在移动的实体接触的物体或让其振动是另一种显示质量和重力的方法地板可以振动，有人坐进去的椅子通过下陷再稍微弹回也可以显示出对重量的反应有时动画师可以晃动摄像机来表明力量的效果考虑角色的大小和重量很重要较重的物体如大象大部分时间都在地面上，而较轻的角色如兔子大部分时间在空中忙碌的兔子很难显示出重力和质量的效果9. 花时间表演动作我们很容易只是坐在电脑前，努力解决人体动画的所有问题站起来，实际表演一下动作，会给动画注入活力这会让角色的动作显得更为独特，也可以解决许多时间和位置安排问题。