This week, in my senior project, I worked on building a belt clutch to be added to the final scene. I rigged it using IK handles, and expression-driven animation. Hit the jump to see a playblast of the clutch in action.
I had some really interesting problems with working on the belt clutch that gave me a much better idea of how IK Handles work. The first issue I had was that they have a quirky tendency to influence joints from parent to child no matter which joint is bound first, but they still act differently either way.
I also hit rough patches in parenting IKs to the belt clutch because they tended to change the orientation of the objects that were following them, when they were supposed to stay on a fixed axis. The easiest way to fix the object to an axis is to have it follow a control ring that has its attributes locked. However, any translations to that control ring won’t show up in the attribute editor, so if you plan on parenting a control ring to a joint and then using an expression based on the control ring, it won’t work.
My solution has been to just use the object in question for the parenting because its attributes still change when it moves. So the process has been to constrain the IK with a keyframe, parent a control ring to the IK. Then I would lock the control ring’s attributes and parent the object to the control ring.
This is all clearly demonstrated by my amazing infographic below.
Now that I know how to use complicated rigs similar to the ones in the belt clutch and the steam engine, I have a pretty good idea of how to run them again. In the future, I may make a tutorial on it, because I had a difficult time finding out how to do it on my own.