• Adobe After Effects Expressions

  Wheel rotation expression problem

  Posted by Paul Gale on February 1, 2012 at 12:53 pm

  Hi,

  I have a racing car animation with the wheels on the cars rotating based on their width and position in the x axis (based on the great tutorial by Carl Larsen – thanks Carl!). There’s also a random offset so the wheels are in a different rotational position on each car.

  The expression is shown below.

  The car and wheels are in their own comp which is then nested in the “main” comp which is a 3D comp. The wheels rotate correctly in the main comp when the car is dragged in the x axis (by physically moving the car in the comp window etc) BUT when the x position is animated (stopwatch turned on), the wheels don’t rotate although they do rotate in the correct way if I view the nested comp! It’s as if the nested comp isn’t getting updated correctly in the main comp.

  What am I missing? Is it something to do with the nested comp referencing the main comp or a bug or something I don’t understand?

  Any help MOST gratefully received 🙂

  Thanks,

  Paul.

  d=width;
pi=Math.PI;
circ=d*pi;
rot=360/circ;
seedRandom(12346, true);
offset=random()*360;
movex= comp("Main").layer("blue car").transform.position[0];
scaler= comp("Main").layer("blue car").transform.scale[0]/100;
(rot*movex/scaler)+offset;

  Paul Gale replied 14 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  February 1, 2012 at 3:43 pm

  It works for me. What version of AE are you using?

  Dan
• 

  Paul Gale

  February 1, 2012 at 3:47 pm

  Sorry Dan,

  My posts are currently moderated and in the time it’s taken for this post to appear, I’ve discovered the problem – my car comp was offset in time in the main comp – so the wheel animation was actually happening but much later in the comp – duh! Stupid but one of those thing that can take ages to track down. All working now – I love expressions, so cool when you get something relatively (for me!)complicated working 🙂

  Many thanks for the reply though 🙂

  Paul.

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