Lesson 6: Laying out Joints and Making IK Handles

Lesson 6: Laying out Joints and Making IK Handles

Laying Out the Joints

              In this video, I demonstrate how to make a set of joints for a humanoid torso.

Making an IK Handle

               I say that I will show you how to  make an IK Handle, but ran out of time. The set up for the wrist is about what you would do for the joints of an arm.

References:

Immel, Brian J.Forward and Inverse Kinematics.N.D.http://www.jawa9000.com/Technical/fk-ik-arm/fk-ik-arm.htm

Helpful Tip When Using IK Handles

Helpful Tip When Using IK Handles

Keep in Mind

             Knowing when to work with IK Handles will become more important as you learn more rigging techniques. Keep this concept in mind when laying out a characters joints because knowing where you will put your controllers and what type helps to make working faster. Always keep a look out for what is happening around you so you can learn from nature and replicate movements as much as possible.

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/

Lesson 4: Joints

Lesson 4: Joints

Joints:

                Joints in Autodesk Maya allow you to make skeleton like structures. These structures can be used for characters or objects. You first must build the structure separately as joint chains parented together with control structures, and then you bind it to the mesh to make your model move. We will look at how to make joints and some key points to keep in mind in this lesson.

                You make joints using the Joint Tool found under the Skeleton Tab. The Joint Tool will only allow you to make joints right on the grid. If you are in the Perspective view panel, then any joint you make will be on the grid you see in the center. In order to make a joint chain upright or floating in space, you have to switch between you Front view, Side view, and Front view panels. Every joint you make is parented to the one before it. You can always tell which joint is the child because the parent always points to the child joint.

                You might at some point be tempted to freeze the transformations on a joint, but you should not freeze a joint’s translational values. If you freeze the translational values, then it will go to the same place as the parent joint or the World Origin, the center of the grid. You do not want rotational values on a joint, so if you find a point where moving them is necessary, then freeze only the rotational values. You need to rotate a joint directly when you are placing joints in the places you want them, otherwise you want controllers constraining them. Controllers will be discussed in the next lesson.

Making a Joint Chain:

Step 1: Make sure you are in the Animation Menu, and then go to the Skeleton Tabà Joint Tool

Step 2: Find the view you want and create a set of joints

Step 3: If you feel these need to be tweaked, then change their positions to suit your needs

Step 4: Freeze the rotations if you made any

References:

 Athias, Delano.(2010).Building the Skeleton.http://www.digitaltutors.com/11/training.php?vid=19147&autoplay=1

Lesson 3: Expressions

Lesson 3: Expressions

Expressions

                Expressions are useful tools in Autodesk Maya to make specific changes to an object. “Expressions are program-like instructions you create to control keyable attributes over time. Expressions can be comprised of mathematical equations, conditional statements, or MEL™ commands (Getting Started in Maya, 2010, 625).” MEL stands for Maya Embedded Language, and it is not hard to learn. The “keyable” attributes are those like translate, rotate, and scale. Expressions give way to more complicated steps than just following a driver object.

                 Let us say there are two gears that you would like to turn, gearA and gearB. You would like it to look like gearA pushes gearB, but an Orient Constraint will not allow you to make the rotation look right. The reason the gears do not look right is due to the fact that they share the same rotation values, and thus looking like wheels rather than gears. If you go into the Expression Editor and write an expression saying that the rotation in the axis you need of gearB is equal to the rotation of the same axis of gearA times negative one, then you will see a much more realistic set of gears.

Making a Set of Gears Using an Expression:

Step 1: Make a Polygon Cylinder. Go to the Create Tab à Polygon Primitives à Cylinder

Step 2: Make the Menu set to Polygons by selecting it from the drop down menu.

Step 3: Right click over the cylinder, and use the Faces selection mode. Select ever other face on the cylinder.

Step 4: Extrude the faces. Go to the Edit Mesh Tab à Extrude

Step 5: Hit the Q button and then hit the R button to scale the extruded faces to your liking.

Step 6: Name the gears, and then go to the Window Tab à Animation Editors à Expression Editor

Step 7: Type in the window similar to the following. Hit the Create button and try it out.

References:

(2010).Getting Started in Autodesk Maya 2011. Autodesk , Inc.

Lesson 2: Parent, Orient, and Point Constraints

Lesson 2: Parent, Orient, and Point Constraints

Parent Constraints:

             A Parent Constraint as described in Lesson 1 makes a connection that affects the translation and rotation values of the driven object. The Parent Constraint has its own option window that can be accessed by clicking on the little white box beside the name of the constraint. If you look at the first option in this window, you find “Maintain Offset.” Maintaining an offset refers to the position of the driven in relation to the driver. When this option is turned on, the driven stays in the same place, but if you turn it off, then the driven will snap to the driver. The other areas you might take an interest is the “Constraint Axes” half of the window. This will limit the influence of the constraint.

Orient Constraints:

            An Orient Constraint acts similarly to a Parent Constraint in how it makes a connection, but Orient Constraints only influence the rotational values. These values are an exact match from the driver to the driven, which sets it apart from a Parent Constraint and Parenting. In a Parent Constraint or Parenting the driven will orbit around the driver like the moon around the Earth, but the Orient Constraint does not have that effect where it is in space besides the “Maintain Offset” option in the option window. The areas you will need to know are the “Maintain Offset” and “Constraint Axes.”

Point Constraints:

            A Point Constraint makes a connection similar to the Parent and Orient Constraints, but a Pont Constraint only changes the transnational values of the driven object. The driven object will follow the driver object, but will not affect the rotational values of the driven object. The only areas that you will need to know are the “Maintain Offset” and “Constraint Axes.”