TAILIEUCHUNG - Essential LightWave 3D- P15

Essential LightWave 3D- P15: What you have in your hands is, quite simply, a collection of tools and techniques that many professional LightWave artists use every single day doing what we do in our various fields. The tools and techniques explored in this book are essential to creating the caliber of imagery that you see on film and television and in print and video games. | Chapter 16 Note Figure 16-16 Some have had great success with using limits to restrict how far a bone will bend in a given angular direction. However without the ability to cushion these limits the resulting motion of an item as it reaches its limit is often sharp and inorganic. So I tend to shy away from using limits whenever possible opting instead for well-planned models and cleanly executed animation. Number of Axes Solved When you have two or more joints in an IK chain operating in 2D space things tend to work quite well. But in three-dimensional space the level of complexity of the calculations that IK must figure out rises dramatically. If you want things to work dependably you re going to have to curb your demands on the IK solver. If you take a look at your own arm or leg you ll find that it s built much the same way as the above illustration. Your bicep and thigh can swing back and forth and up and down two axes heading and pitch while your forearm and calf move only around one axis of the elbow and knee respectively. I ve found that referencing real life in building riggings helps more than nearly Figure 16-17 408 Layout 3 Character Animation Figure 16-18 anything else in making character setups that do what you d expect them to do. While the desire to use IK on shoulder or hip joints in order to solve for all three axes heading pitch and bank is tempting I find that often though not always this makes for a loose swively hard-to-control arm or leg. Most often character riggers will leave the bank axis to be controlled manually by the animator using FK. This lets you precisely control the position of the elbow or knee joint just by rotating the bicep or thigh. So the rule of thumb for good solid IK chains in character riggings is The topmost item can use IK to solve for a maximum of two rotation axes and the child item in a character IK chain should use IK for only one axis. Note I don t recommend using standard IK on a bone chain consisting of more than

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