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Activity Forums Adobe After Effects Expressions accordion bar telescoping expression(s)

  • accordion bar telescoping expression(s)

    Posted by Adam Stockett on September 23, 2008 at 6:29 pm

    newbie to expressions…

    i’d like to animate an ‘accordion bar’. like the old monty python boxing glove on an accordion bar that telescopes to punch. it’s hard to explain, but it’s similar to a shaving mirror that you might have on a wall that telescopes out.

    i’m sure this can be accomplished really well with expressions, but it’s beyond me. any help will be greatly appreciated.

    thanks in advance

    Adam Stockett replied 17 years, 7 months ago 3 Members · 3 Replies
  • 3 Replies
  • Dan Ebberts

    September 24, 2008 at 1:50 pm

    OK – let’s say you have a handle piece (called “top handle”) on the left with its anchor point in the center, then you have a bunch of extender pieces, arranged end-to-end, each with their anchor points at the left edge.

    The handle is the parent of the first extender piece, which is the parent of the next extender piece, etc.

    The first extender piece gets this rotation expression:

    -2*parent.transform.rotation

    The rest get this one:

    -parent.transform.rotation

    Then you just rotate the handle to get the extender effect.

    Then you can duplicate the whole thing and give the bottom handle this expression:

    -thisComp.layer(“top handle”).transform.rotation

    That should get you started.

    Dan

  • Eric Sanderson

    September 26, 2008 at 2:40 pm

    What your looking for is Inverse Kinematics, heres a good link on how to do that. Along with alot of great scripting examples and info.

    https://www.motionscript.com/expressions-lab-ae65/ik.html

  • Adam Stockett

    September 26, 2008 at 6:10 pm

    thank you so much dan. like i said.. i’m a beginner with expressions, so i couldn’t really get it to work like it should. but, with your expression help, i’m able to work something out that is much closer. i had to do some things a little different, but basically that scripting on the rotation allows the IK effect and i’m able to work with that.

    thanks again.. ur help is invaluable.

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