• Adobe After Effects Expressions

  particles follow a spiral path

  Posted by Carlos Burrola on February 24, 2009 at 4:30 am

  hi guys, after a lot of searching on the web i didnt find a tutorial on how to make particles(trapcode) follow a path, in my case is a spiral, i already saw the andrew kramer tutorial “the ring” he use a preset, “3d orbit” but i new to after effects and i try to change the values on the expresion but i cant make it works, so if somebody please help me with this, i realy apreciated, i need this for a spot that i have to finished after friday, so im very frustated.

  greetings from mexico.

  Carlos Burrola replied 17 years, 2 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Brendan Mccullough

  February 24, 2009 at 3:26 pm

  Option 1: Create a spiral to your liking in Adobe Illustrator, copy the path, and paste it on the position property of a Null, and parent the position of particular (in the effect, not the layer) to the position of the Null.

  Option 2: Use this expression for your particular position (this will require some experimenting):

  freq = 10;
amp = 10;
multiplier = 1.5;
x = Math.sin(time*freq)*(amp*multiplier);
y = Math.cos(time*freq)*amp;
[x, y];

  You could link the freq, amp, and multipler values to sliders with the pickwhip to experiment a little more easily.

  I haven’t tried this myself because I’m in the middle of digitizing for an edit right now, but I think it should work.

  Good luck! I hope you make your deadline.
• 

  Kevin Camp

  February 24, 2009 at 5:12 pm

  here’s a thread from the ae forum that discusses doing something similar… about half way down, starting with a post from Francisco Cueto is the part you’d be more interested in.

  he was trying to create an upwards spiral (he described as christmas tree-like) by using parented nulls (one rotates and moves upward, the second is parented and moves horizontally). then getting the values of the parented null to be used by the emitter.

  it may be easier to adjust the movement of the nulls to effect the emitter, than to adjust an expression… it just depends on what you’re comfortable with…. but the basic set up for the null would be like this:

  1. create a new null (layer>new>null), and then another and make them both 3d layers (click the 3d cube check box for each layer).
  2. select the first null (‘null 1’) and animate the rotation on the x, y or z axis as needed.
  3. use the parenting pickwhip (or dropdown menu) of ‘null 2’ to select null 1 as it’s parent. this will link the rotation of null 1 to null 2.
  4. offset the position of null 2 along the axis that is perpendicular to that of null 1’s rotation (ex: if you rotated around the y-axis, offset null 2’s x-pos). this will set the diameter of the spiral.
  5. to create the sprial, animate the position of null 2 on the same axis as null 1’s rotation (by the ex: animate along the y-axis)

  then follow the steps outlined in the post i linked to to set those values as the emitter’s position. to make adjustments to the spiral, just modify the properties of the nulls… by the example: to make it spin faster increase the y-rotation of null 1. to change the diameter, adjust null 2’s x-position.

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Carlos Burrola

  February 25, 2009 at 1:22 am

  hey brendan, tnx a lot man, you save my ass, hehehe, i tried the op. 1 and it works perfectly, im gonna try the other one later, just to see how much the animation can change. tnx again.

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