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Artist q&A
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ARTIST Q&A

Is It possIble to set up Ik on a cHaIn

WItH more tHan four joInts?

Michael Smith, Leeds

If you’re struggling with longer joint chains,

maybe the spring solver is the answer

locked to the ground. Not impossible but

still not an easy task.

Traditionally, IK works best with a

simple three-joint chain where the solver

calculates the rotation of each joint in the

chain. What is less known is that you can

use more joints and the IK solver will try

to adapt. If you increase this to four joints

the solver will work if the angles of each

joint are great enough. Try to use more

than four and the chain breaks down, so

the joints in the middle either don’t get

evaluated or don’t rotate correctly.

So, what’s the solution if you need to

use more than four joints? Yes, you could

use an IK spline solver but this is very

specific to the type of chain you are using it

on, so this wouldn’t work on anything that

When it comes to animation,
inverse kinematics, or IK as it’s
more widely known, is a huge time saver.
Being able to move a character’s hips while
the feet stay planted, or keeping its hand
steady on the balustrade as it ascends
the stairs, not only makes an animator’s
life much easier, but it can also help to
produce more believable movements
quickly and efficiently.
IK allows the animator this freedom
because unlike FK (forward kinematics),
the joints are evaluated in reverse. So, with
FK you would move the hip, then the knee
and finally the foot whereas with IK the
foot is evaluated first, so the chain works
backwards. Imagine trying to create a walk
cycle using only FK and keeping the feet

has a distinct bend, like a knee or elbow.

Luckily, there is another solution available

for us in Maya.

Hidden away in the deep recesses of

Maya’s libraries is another IK solver, the

spring solver. Once loaded, this secret

solver will appear in the IK Handle options

and can be applied just as you would with

any other IK handle.

On first appearances it will look the

same, except the key difference here

is that it is specifically designed to

work with longer joint chains. What it

does is keep the angles between the

joints proportional, to ensure they are

distributed evenly.

Let’s have a look at how to create and

edit a long joint chain.

Antony Ward replies

SOFTWARE: AUTOdESK mAyA