I'd like to thank my friend and Character Artist, Miki Bishop, for letting me use her character for this series.
Happy Tech Art Tuesday!
Also happy birthday to me!
Leg IK/FK Switch + Twist
At first I was going to show only a fast-forward of me doing the legs. Since I wasn't satisfied with the video for the arm twist, I had the idea of using the legs as a opportunity to explain it better.
I already built the IKFK switch setup for the left leg prior to recording this. I'll be posting that this Thursday as a refresher.
As explained in the video, the setup has two extra joint chains: the bind chain ("BND"), which will eventually hold skinning information for the leg, and the twist chain, which is under the influence of an IK Spline curve.
The spline curve has clusters that are parent-constrained to the green square controls. When we translate the controls, it translates the clusters, which translate the curve's control vertex, which translates the twist chain, which FINALLY translates the BND joints. Get it? :D
An advantage of using the Spline curve for the twist is that we can use the arcLenght of the curve to scale the chain in X if we need to. This is achieved with the following node network setup:
Now the rotation will be a bit different.
When I make arms and legs with twist joints, I like to mimic supination and pronation.
For this setup, I grab the rotation X of the knee and plug it into a multiplyDivide node that reduces it by a percentage of my choosing; I then plug the output into the BND joint. I sometimes to one multiplyDivide node per BND joint, sometimes I reuse the same node for multiple joints (like I did in the video).
Note: If we're dointg the last BND joint that sits on top of the original knee, we don't need the multiplyDivide node because that joint will mimic the exact rotation of the knee.
While that's cool and stuff, I still want my animator to have some control over the rotation of the leg. So I'm going to make yet another node network that adds the output of that multiplyDivide node to the rotate X of the green square control:
Like I mentioned, the last BND joint (the one sitting on top of the original knee), doesn't have a multiplyDivide node to go through, so it'll look slightly different:
I'm gonna eat some bday cake and spaghetti with hotdogs! Farewell!