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1/26/10 4:26 PMMaya Skeleton Setup

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Maya Skeleton Setup

Setting up a skeleton for your character and binding it to the skin.

My name is Larry Neuberger and I am a professor at Alfred State College in Alfred NY. I created these handouts to use in myclasses and most of my students found them to be helpful. I now decided to submit them to be published on the web hopingthey can help others as well. This lecture will go over creating a skeleton for your character and attaching it to the skeleton using the bind command. Wewill also be discussing the options for each of the bind tools and the sub-tools that allow you to perfect it. Some of you will becreating characters with two legs, four legs, no legs, etc. The easiest way for me to go over all of this is with a basic humancharacter. First, when modeling your character, you want to be sure that you pose him in a “T” shape before you even attempt to createa skeleton for it (See fig 1.). By doing this there will be fewer alterations when binding and your CV’s will not get intertwined.

Fig 1.

Once your character is set up you can begin to build the skeleton. Before you start creating the skeleton you want to setup theoptions for the joint tool. Go to Skeleton > Joint Tool . When the option box is open, set auto joint orient to none (Fig 2.).

Fig 2.



This setting makes sure that joints constrain properly when binding to the skin. Once this is set we can begincreating the skeleton.

Creating the Legs

Now we can begin the actual skeleton. Depending on what kind of character you have, your results will vary. I usually startwith one of the legs. Simply click once to start the skeleton, then click each time you want to place a joint and at thecompletion press enter to finalize it.. See example below for my character’s leg skeleton (Fig 3.).

Fig 3.

You will notice I did not use the reverse foot method like described in the “primitive man” tutorial in the Learning Maya book. Ifyou wish to use the reverse foot, refer to pages 314 – 320. The reverse foot has you create a second bone structure, connectit to the foot, and add an attribute to control the foots roll. I personally like to keep the skeleton rather simple, animate it, thenonce my walk is done, go back and animate the foot’s roll by hand. You should do whichever you feel more comfortable withwhen creating your skeleton. It is also a good idea to name all of your joints when you are done. This makes for easier editing.Use the channel box to name your joints like we learned in earlier lessons. Once you have your leg set up we will want to add an IK handle to it. An IK Handle is a manipulator which makes animatingthe leg easier. Before we add the IK Handle though, we need to have the leg have a slight bend in it so the handle knows howto control the leg. Simply select the knee joint and rotate it a little to create a slight bend in the leg (Fig. 4).

Fig. 4.



Once the bend is completed you will need to set the preferred angle. Setting the preferred angle tells Maya how to control theleg’s movement. In this case we are saying to bend at the knee. Select the whole leg skeleton, then go to Skeleton > SetPreferred Angle. (Fig. 5)

Fig. 5.

Now that the angle is set, we are ready to add an IK Handle to the chain. Simply go to Skeleton > IK Handle Tool. (Fig. 6)Then click on the top joint, then on the joint where you want to end the bending (the ankle joint). Once that is done you willsee a thin line going from the Hip joint to the Ankle joint. This is what you will Use to control the animation of the entire leg.Select the handle and move it to see how the leg reacts (Fig. 7).

Fig. 6. Fig. 7.

We now have an IK Handle set up on the leg and we are almost ready to animate with it. We just need to rig it now. Beforewe go into rigging it we will just go over what and where a few things are. (Fig. 8)

The pole vector starts at the start joint, and with the handlevector defines the reference plane.

Because moving the pole vector changes the orientation of the



Fig. 8. The pole vector effects the skeletons rotation around a certain plain. At it’s default settings, the pole vector faces forward and createsan invisible plain that it will rotate around. See figures 9 and 10 below for a better explanation.

Fig. 9. Fig. 10.

reference plane, moving the pole vector can also change theorientation of the joint chain directly, just as manipulating the twistdisc can change the orientation of the joint chain. This is becausethe joint chain's degree of orientation, or twist, is defined as thedifference in orientation between the reference plane and the jointchain plane.

The twist twist discdisc is located at the end joint. The twist disc is amanipulator for twisting the joint chain by rotating the jointchain plane.

Fig. 5 above shows the IK Handle pulled up andthe leg deforming properly. You can see it isalmost at the plane of the pole vector.

Fig. 6 shows the IK Handle moved above theplane of the pole vector. Once it moves abovethe pole vector the leg is flipped and notproperly aligned.



What we want to do is change the direction the pole vector is in which will allow the leg to rotate freely and unchanged. To dothis, select the IK handle and press the show manipulator button (Keyboard shortcut T). (Fig. 11.) Then move the pole vectorso it is pointing inwards facing the body’s center (Fig. 12.).

Fig. 11. Fig. 12. Now the rotation plane is going perpendicular through the leg. So now when we move the IK handle to rotate the leg we willhave no undesirable changes. The only problem is now the leg is facing inward and kind of pigeon toed. This is where the twistdisc comes into play. While the manipulator is showing, use your left mouse button and click and drag to rotate the twist discso the leg is facing forward (Fig. 13).

Fig. 13.

Notice how the Pole Vector is now facing inwards. Now if we grab the IK handle and move it, the leg will rotate properly with nonegative effect on the skeleton. (Fig. 14 – 15)

Fig. 14. Fig. 15.



Now that the pole vector is going perpendicular through the skeleton, it will allow it to rotate a full 360 degrees without anddeformations or tweaking as compared to before when it was facing forwards.

Setting Limits on a joints rotation.

Now that the leg is all set with an IK handle and ready to animate, it is a good idea to set limits on certain joints so it cannot bend tomuch an over extend itself. Right now, with no limits set, the knee is able to bend more than it should as well as over extend itself (Fig.16 – 17.).

Fig. 16. Fig. 17.

We can now set limits on the knee joint so this does not happen and we get a more realistic movement on it. Select the knee joint andopen the attribute editor for it by going to window > attribute editor. (Fig. 18.) Once the attribute editor is open, go to the sectionlabeled limit information (Fig. 19.).

Fig. 18. Fig. 19.

You can see in the limit information section in the attribute editor, you have minimum and maximum values for the joint. Select the IKhandle and move the leg to the maximum rotation in the reverse direction (Fig. 20.). Then select the knee joint and go back to thelimit information in the attribute editor. Press the arrow next to max and then check the box next to it (Fig. 21.).

In Fig. 16 you can see the knee bends toomuch in the reverse directions.

In Fig. 17 the knee hyper extends when pulled forward.



Fig. 20. Fig. 21.

You have now set the maximum rotation for that joint. Repeat the steps above for the minimum rotation. Select the IK handle andmove the leg in the opposite direction (Fig. 22.). Then select the joint, go to the attribute editor, and using the same steps as above,set the minimum limit (Fig. 23.).

Fig. 22. Fig. 23.

That is all there is to it. We now have a leg with an IK chain set up on it which rotates with no tweaks and has limits set to avoid overbending and hyper extension. So if you try to bend the knee backwards by moving the IK handle, you will see it will stop at themaximum limit we just set (Fig. 24 - 25.).

Fig. 24. Fig. 25.

NOTE: Now all you would have to do is repeat the same steps for the arms and your skeleton will be ready togo. None of this is necessary nor required when rigging a skeleton, but by spending the extra time to do this,



animating will be that much easier for you in the long run. Now that the one leg is complete, we will duplicate it to the other side. There is no reason we need to go do all this workagain. Select the entire leg by clicking the main joint (Fig. 26), then go to Skeleton > Mirror Joint . (Fig. 27) Once the optionbox is open, select the appropriate mirror across selection. If you are not sure, try one at a time until you get the right one.

Fig. 26. Fig. 27.

Once you have the appropriate mirror across selection, press apply and the entire joint (along with the limits, IK, Twist Disc,and Pole Vector) will duplicate and mirror to the other leg (Fig. 28).

Fig. 28.

Creating the Torso / Spinal Column

Now that the legs are set we can work on the torso area. Use the joint tool again to create the spinal column / torso (Fig. 29).



Fig. 29

Once you have the torso done, notice all the space to the left and right of the spinal column. Later on when we bind the skinto the skeleton this could cause problems. To help reduce the space from the column to the edge of the skin it is helpful to adda rib cage. This is not required, but once again, extremely helpful and will make animating that much easier andflawless later on. To do this, use the joint tool and select a joint on the spinal column to start with, then click away from it to create the rib bone(Fig. 30). Repeat this until you have a full rib cage (Fig. 31).

Fig. 30. Fig. 31.

Creating the Legs and Hands Now we are ready to create the bone structure for the arms and hands. In order to do this we will repeat the steps we used tocreate the legs which I will go over briefly again.

Fig. 32

Using the Joint tool (Skeleton > Joint Tool), clickjoint by joint to create the skeletal structure forthe arms and hands. Don’t forget to name thejoints using the channel box when you are done.



Fig. 33

Fig. 34

Fig. 35

Once the arms is complete, bend the elbow aslight bit using the rotate tool. Then go to Skeleton > Set Preferred Angle.

Next, go to Skeleton > IK Handle Tool.



Fig. 36

Fig. 37.

Fig. 38.

Then click on the main joint (the shoulder), thenthe wrist joint as the end effector. You should nowsee a thin line connecting the shoulder to the wrist(the IK Handle). Select the IK Handle, then press the showmanipulator tool and drag the pole vectoroutwards towards the hand. Remember, the polevector acts like the top bar on a swing set. Bydoing this, when you rotate the arm, you will notget any unwanted twists or tweaks.

Now set the limits on the arm. Select the elbowjoint, open the attribute editor and set theminimum limit.



Fig. 39.

Fig. 40

Fig. 41.

Then select the IK Handle, bend the arm inwards,select the elbow joint again and set the maximumlimit for that. Now we can mirror the arm to the other side.Select the Arm’s root joint, then go to Skeleton >Mirror Joint .

Select the appropriate mirror across selectionand press apply. Now the arm is mirrored across to the other



Fig. 42.

Connecting the Joints Almost finished!!!!! We now have a skeleton, but the arms and legs are not attached to the rest of the skeleton. To do this,start by selecting the leg’s root joint, then shift click on the torso’s root joint (Fig. 43)

Fig. 43

Next, go to Skeleton > Connect Joint to open the option box (Fig. 44). Once it is open, select parent and select apply toconnect the two.(Fig. 45)

Fig. 44. Fig. 45.

The difference between Parent and Connect is as follows:

Connect Joint

Now the arm is mirrored across to the otherside.



Connects the selected joints and moves the joint chain of the first joint to the position of the second joint. Afterconnecting the joints, use Remove Joint to delete the extra joint.

Parent Joint

Connects the selected joints by inserting a new bone between them.

Repeat these steps for the other leg and arms to complete the skeleton (Fig. 46).

Fig. 46.

Constraining a Pole Vector

This is a very simple and effective tool for use with animating. Sometimes when you move an IK Handle on a joint the structurerotate a bit out of proportion. In order to fix it you would have to select the IK Handle, then show the manipulator, then usethe twist disc to fix it. This will happen, so it is better to put more work in the skeleton setup and rigging so animation will gosmoother, faster, and easier.



Fig. 47

Fig. 48

Fig. 49

Go to Create > Locator. Position the locator behind the joint where you wantit placed. Select the locator, then the IK Handle (It most be inthis order. If you select them out of order this willnot work.).



Fig. 50

Fig. 51

Fig. 52

Now your skeleton is setup, rigged, and ready to be bound to the skin. In the following handouts we will go over the differentbinding methods. Remember, this may look like a lot of work, but it is well worth it. The time and work you put into the setupand rigging of the skeleton, the less problems you will have when animating. The smoother the rig, the smoother thananimation process will be.

Next go to Constrain > Pole Vector. Now select the locator and move it to test theresults. You will see that when the locator ismoved the arm rotates. This will help later whenanimating if your joints rotate out of position.(Something like this will happen, so it is best todo this and be prepared.) Your finished product should look something likethe image to the left.

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