Easter Project 05

A couple of final new things I learnt about while making this rig.

On problem I have always found a pain in 3D is that the IK legs pop over when the controller at the ankle passes the hight of the pole vector (the origin of the IK set up that dictates the direction for the knee to point generally located at or around the pelvis). There is such a simple solution to this I can't believe it not used more often. Here is a comparison between the standard IK set up and my non flip IK leg.

Another thing I learnt about was the advantages of having an extra joint at the elbow or knee.

See in these examples (screen captures from the DVD I have been referencing - Rigging for Feature Animation from Fahrenheit Digital) how having a single joint is fine for a 90 degree bend but you get an ugly overlap in the mesh when you bend the limb further.

In the past I have gotten around this with the weights on the mesh (determining how the mesh is influenced by the bones), but this way makes much more sense.

You don't have to animate the extra little joint, it is set up to inherit rotation from the for arm, so to animate its no different that a two bone joint. I have always tried to avoid IK control for a 3 joint limb, but I have learnt that as long as you keep your local rotation axis lined up through the length of the limb (something I hadn't even considered before) then they work just fine.


I'm not sure how much of this I'm going to be able to cover in class because of the time constraints (really we only get about 160 class hours devoted to just 3D and I think I already try to squeeze in to much) so make sure you ask me if there is anything here you want to learn more about and maybe we can get together outside of class time at some stage and talk about it. Also any ex students who want to know more about any of these things can leave a post on the Forum and I'll do my best to help you out.

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