Spline IK Setup in Maya
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Advanced Discussion and Useful Tricks
Particle Collisions
In the event that you have multiple spline IK chains, you might want them to collide, not only with other objects but with themselves, too. You can do this using the particles as the source for a radial field. This is an old trick, but it seems to work fairly well. Be warned, though: Particle collisions will definitely slow Maya down.
A radial field basically gives the particle the ability to have boundaries. You can make these boundaries collide with each other. Select your particles and create a default Radial field.
Change these attributes in the channel box:
Attenuation: 0
Max Distance: 1 (think of this as the particle radius)
Apply Per Vertex: On (this means for each particle a radial field will be created).
Radial Type: 1
Finally, select the Radial field together with the particle object, and from the Fields menu, choose "Use Selected as Source of Field."
Your particles will now collide. You can do this multiple times to affect multiple spline IK setups. You can also create collision events on rigid bodies if you want the spline IK to be affected when it hits something.
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Non-Destructive Rigging
Instead of destroying what you've already done with your character, you might consider using spline IK in addition to your other controls. Simply create a new chain on top of your already existing skeleton, then go from there. You can group your existing joints and then constrain those joints to your new joints so that they follow. The catch to this is that everything must be oriented the same way. This concept works well if you only want your spline IK for a particular shot, or if you want to retain a certain amount of control.
Spline IK Handle Attribute Animation
Take full advantage of the situation when animating with your spline IK. On the handle itself, there are several attributes that can be very helpful:
offset: This offsets the curve, thus taking your object with it, good for "snake-like" animation.
roll: this rotates the IK handle from the base, rotating the bound object around.
twist: the twist attribute is good for tentacle animation. It twists the joints from the base to the end of the chain, causing your object to twist around itself.
Using Multiple Levels of Control
If you are using more than one spline IK chain, then it would make sense to have several layers of control for animation. The first level of control would be the clusters. You could then divide up the clusters into groups, parenting them to multiple objects, allowing you to move multiple clusters at once. Finally, you could go even farther and make yet another level of control which would group those higher groups into smaller groups, allowing for a broader spectrum of control. Try to keep your controls friendly to the eye -- use nurbs curves of different shapes to differentiate between the levels of control.
Dynamic Springs
If you are experienced with Maya Dynamics, then you should be familiar with how springs affect a Soft Body object. You can use them to attach particles to the object, or create tension from particle to particle. Using springs, you can gain a great level of control over your Soft Body spline IK object. Maya's help documentation has detailed explanations covering Springs and how they will affect your particles.
Scale and Hierarchy
If you want to be able to scale your Spline IK setup, then you'll need to make sure it is completely out of the hierarchy of your character rig. Even if you don't necessarily want to scale, it is still a good idea to keep your IK handles and spline curve always in a group that will never be moved from its origin. Scaling a rig is something you want to avoid anyway. Use constraints as an alternative to parenting when you can. It will really help you in the long run.
Joe Harkins is currently a "puppeteer," aka Creature TD, at Tippett Studio, in Berkeley, CA, working on The Matrix Revolutions and other film projects full time. His background is in character setup and animation for commercials and film. Prev 1 2
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