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The technique used for the IK spline tail and ears setup is a very common combination of IK splines, with some added FK-style control. The technique you will use in the next exercise is basically to create a spline IK for the entire hierarchy of joints and then draw a low-res joint hierarchy right on top of where the IK spline curve was created (usually two to three joints is enough). Next, you'll simply smooth-bind the low-res joints to the IK spline curve. This is a nice way to get some FK feeling control and still have the ability to translate the joints for IK spline-style results.
Exercise 17.2 Character Setup for Spot's Tail and Ears This exercise again is performed only on the tail. The exact same technique should then be used on the ears as well.
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As the following exercise shows, creating stand-in geometry is a very simple process. This geometry is simply a low-resolution version of the actual character geometry, which is then cut up into a separate piece per joint using a combination of the Cut Poly Faces tool and the Poly Separate command. The cut polygon pieces are then simply made a child of the joint that they correspond to. Now, the low-res geometry moves with the joint hierarchy but is not bound or deforming, so it is extremely fast and interactive for the animator to use.
Exercise 17.3 Creating Low-Res Stand-In Geometry
For this exercise, you begin with the finished file from the previous exercise, Dog_TailAndEarSetup_Finished.mb, which you can find on the accompanying CD.
Import into the Dog_TailAndEarSetup_Finished.mb file the low-res dog file, called Dog_lowResPolyStandIn.mb, which you'll find on the accompanying CD (see Figure 17.13).
Figure 17.13
A low-res version of the character model is used for the low-res
stand-in geometry.
Take a look at the joint hierarchy of the dog, and start to figure out where you want to cut your low-res poly object into separate pieces. A general rule is that you will need to cut your character in any place that it will need to bend, or any child that will need to rotate independently from its parent to achieve the articulation of the character's pose.
Select the low-res polygon character. Activate the Cut Poly Faces tool by clicking Edit Polygons, Cut Faces Tool (it might say just Cut Faces, depending on your tool settings) Option Box (see Figure 17.14).
Figure 17.14
Select the low-res polygon character, and activate the Cut Poly
Faces tool.
Now, with the options from the previous figure, drag your mouse across the geometry and watch as the Cut Faces tool creates a straight line across your geometry. This is where the polygons will be cut when you release the tool. Cut the polygons. Experiment with where you are cutting the geometry and how well it lines up with the location of the joint.
Next, after you have cut the polygon, perform the menu commands Edit Polygons, Separate and then Edit, Delete by Type, History.
Cut the geometry into a separate piece for each joint, trying not to cut across other parts of the geometry that shouldn't be split yet. Then, each time you cut, separate the polygons and delete the history. Eventually, you will be finished cutting up the entire geometry.
Next, one by one, select each polygon piece that you cut, and Shift+select the closest joint that you cut that piece for. Hit the p key on your keyboard to parent the geometry to the joint. Do this for each separate piece that you cut for the character.
You can find the finished file with the low-resolution stand-in character properly cut and parented in the file Dog_LowResStandIn_Finished.mb on the accompanying CD.
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Created: March 27 2003
Revised: November 7, 2003
URL: http://webreference.com/3d/insidemaya/1
