Lesson 5: Creating Joint Controllers

Lesson 5: Creating Joint Controllers

Controllers:

                Whenever you are making joints, you always want to build controllers so that you are not grabbing the joints directly. You can make one of two types of controllers, Forward Kinematics and Inverse Kinematics.

                Forward Kinematics refers to a system of controllers in which each controller moves one joint. When moving something like an arm would mean that in order to reach a position, you would first rotate the shoulder. Then you would rotate the elbow, and finally the wrist. The controllers are usually made from NURBS Curves, which are much different from Polygon Primitives. "NURBS stands for Non-Uniform Rational B-splines(M5 Design Studio, 2011)." NURBS Curves do not render in Autodesk Maya. They are simple objects and many do not have faces. You want to use either an Orient Constraint or use an Expression, depending on the situation. Forward Kinematics allow for move direct control.

                Inverse Kinematics controllers are created by the IK Handle Tool found under the Skeleton Tab. The IK Handles allow for a set of joints to be controlled by a single controller. If you had that same arm set and you used an IK Handle, you would be able to control the arm at the wrist. You would have a NURBS Curve that controlled the handle using a Point Constraint and an Orient Constraint on the wrist so the hand could rotate properly. There are several types of IK Handles, but describing them would be more in depth than this post can cover.

                When using NURBS Curves as controllers, you want the curve’s X axis to align with the joint’s X axis as you place the controller where the joint is located. The best way to make them align is to first rotate the new curve 90 degrees in the Z axis and freeze the curve’s translations. Then you want to put the curve in a group by going to the Create Tab and find Empty Group. Parent the curve to the group. Use a Parent Constraint with the Maintain Offset turned off with the joint as the driver, and the group as the driven. Once the group is in place, delete the parent constraint. You can find the constraint by going to the Outliner Window and looking for the group. Once you have found the group, you can click on the plus sign to open up the contents of the group. Click the “!” icon and then hit the Delete button on your keyboard. From there you can use the curve to constrain the joint and it will always have a default position.

References:

M5 Design Studio.(2011).NURS Modeling in Maya 3D 2012.http://m5designstudio.com/2011/maya-3d-tutorials/nurbs-modeling/