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Forums Adobe After Effects Expressions Is it possible to have an IK rig with 4 nulls?

  • Is it possible to have an IK rig with 4 nulls?

  • James Pierson

    June 15, 2022 at 10:17 am


    There seem to be lots of scripts/resources for making a traditional rig, where there are 3 rotation points (eg, shoulder, elbow and wrist). But I was wondering if there is a way to create a 4 rotation point rig, eg for a horses leg?

    For example, if I had all the artwork setup, and placed 4 null objects that would act as the pivot points for the artwork to be parented to, is there an expression/s I can apply in order to rig them up, so that If I moved the last in the chain it would act as an IK?


  • Dan Ebberts

    June 15, 2022 at 1:59 pm

    It’s been quite a while since I looked into this, but as I recall, as soon as you have more than 3 joints (with two segments), you move out of the realm of pure geometry and into iterative algorithms because there are multiple possible solutions. Because of that, there’s an additional complication that the solution would have to be calculated in a single expression and the results somehow distributed to the participating nulls (via text layer maybe?). Not impossible, I think, but definitely much more complex than the the 1 angle/2 segment/3 joint version.

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