Dog Hind Leg Tutorial
By, Tyler Thornock
This tutorial will help you setup a dog/animal's hind leg with a single
control to make it easier for the animator to move. This basically
artificially sets up a spring ik. So if you have Maya 7, you may
want to use it, though this setup does give you more control in the end.
This setup may be confusing for some, but the stuff you learn can be applied
to many other areas.
Well, the first part of this tutorial is "borrowed" from the Inspired
3D Advanced Rigging and Deformations book, however the book does not setup
the rotation of the second part of the leg to be driven automatically
which is a pain because the animator would have to rotate it appropriately
every time they move the leg. With this setup, the animator can
control the rotation or leave it automatic, unlike using a spring ik.
Initial Setup:
- Start out with a four joint chain. Name them Hip, Knee, Ankle,
Wrist with the extension _ikfull.
- Now duplicate the chain and replace _ikfull1
with _ik, this is going
to be the main ik chain, if you were setting up an ik/fk switch, this
is the chain you would blend.
- Next, add an ikhandle from the Hip_ikfull to the Wrist_ikfull and name
it Leg_ikhandle.
- Next, add an ikhandle from the Hip_ik to the Ankle_ik and name it Ankle_ikhandle.
- Finally, add an ikhandle from the Ankle_ik to the Wrist_ik and name
it Wrist_ikhandle.
parenting
- Now that is setup, time for parenting. Parent the Ankle_ikhandle
to the Wrist_ik and the Wrist_ikhandle to the Ankle_ik and freeze transformations
on both of the ikhandles.
- You can now drag around the Leg_ikhandle and have the other chain follow
it. If you rotate the Wrist_ikfull joint it would move the leg appropriately.
Now we need to set it up so it automatically figures out how much rotation
to apply.
- Next create a distance dimension node and snap one end to the Hip and
the other to the Wrist. Parent the one at the wrist to Leg_ikhandle
and parent the other to the Hip_ik (if you have cyclecheck issues, parent
it to the hip pivot or "clavicle" when finished and leave unparented for
now)
Savor the one and only screenshot!
Nodes and Mel!:
- Now we have to get the current value of the distance node so we know
how much closer the wrist is to the hip when being moved then it was at
default position. .... I used a getAttr mel command to do it to make sure
I got all the trailing numbers (ex. 5.34233229) mel code:
getAttr distanceDimensionShape1.distance;
setting up the plusMinusAverage node
- Next, we have to subtract the starting distance value from the one that
is constantly changing. So create a plusMinusAverage node named
Leg_AutoWristRot_pma;
- Select the distanceDimension1 node and add an attribute called "starting
distance" and set it to whatever you got from above.
- Open up the connection editor and load the distanceDimension1 node as
the output and Leg_AutoWristRot_pma as the input. Connect the starting
distance to Input1 D[0];
- Now load up distanceDimensionShape1 as the output and connect the distance
to Input1 D[1]; But oh no! There is no Input1 D[1] to connect it
to! You could use the hypergraph and not have this problem, but
I prefer the connection editor. You have to open up the script editor
and find the line like this (connectAttr -f distanceDimension1.startingDistance
Leg_AutoWristRot_pma.input1D[0];
) copy the line into the bottom part of the script editor and change that
0 to a 1 and run the command. Now if you left the connection editor
open you have an Input1 D[1] which you can connect the distanceDimensionShape1's
distance to.
- Lastly, select the plusMinusAveraege node, open up the attribute editor
and change the operation to subtrace.
setting up the condition node
- Now create a condition node named "Leg_AutoWristRot_con"
mel code: createNode condition -n Leg_AutoWristRot_con;
- Plug in the Output1D value from the plusMinusAverage node above into
the condition node's First Term (using the connection editor).
- Now select the condition node and open the attribute editor. Set
the operation to Greater Than and for all the Color If False values enter
in 0.
setting up the multiplyDivide node
- Almost there. Create a multiplyDivide node named "Leg_AutoWristRot_mult"
mel code: createNode multiplyDivide -n Leg_AutoWristRot_mult;
- Plug in the Output1D value from the plusMinusAverage node above into
the multiplyDivide node's input1X (using the connection editor).
- Now connect the OutputX of the multiplyDivide node to the condition
node's colorIfTrueR attribute.
- Now, connect the condition node's outColorR to the Wrist_ikfull's rotateZ
(it may be a different rotate depending on your orients).
Wrap Up:
- Next, create a control for the leg, snap it to the Wrist, freeze its
transforms and point constraint the ikHandle to the control (select the
control, then ikhandle, and then point constrain);
- Add an attribute to the control called ankleBendAdjust and set the min
value to -30, max to 30 and default to 5 or 10.
- Now connect the ankleBendAdjust to the multiplyDivide node's input2X.
- If you did it right and my tutorial is void of typos you can now grab
the box and move the leg around with the _ik
chain moving correctly!
- TIP: If you want to add a control for the
animator to be able to manually rotate the ankle and avoid the auto all
together, simply create another plusMinusAverage node that adds up the
outColorR of the condition node and another custom attribute and then
connect the plusMinusAverage's Output1D value to the rotate instead of
the condition's outColorR.
NOTE:
Before you bind the joints or continue with adding a footroll, you will
need to create another joint called something like Foot_ik, snap it to
the Wrist_ik and parent it to the Ankle_ik. The reason for this
is that the actual Wrist_ik joint is being rotated in order move the leg
properly and would screw up the footroll if it was the joint all the toes
were parented to. The sample file has the footroll implemented into
the setup.
Sample File from tutorial.
|
