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Activity Forums Adobe After Effects Expressions Finding an intersection of two lines and parenting it

  • Finding an intersection of two lines and parenting it

    Posted by John Burgess on June 3, 2020 at 11:11 am

    Hi, I am attempting to create a Lissajous curve table like the example driven by expressions.
    By rotating a point at different speeds around a circle and tracing the x and y position from each it will generate different curves.

    What I am struggling with is finding the the intersection of the x and y guides in red to then parent a shape layer to and use something like trails to draw them https://aescripts.com/trails/

    I have created the below by parenting the x and y guides to the radius of each circle that has a rotation applied and then offsetting it by the rotation speed so they don’t rotate.

    Doing this removes the ability to easily access the x or y position of the guides as they are being driven by rotation which makes me question if this is the best method?

    Thanks.

    thisComp.layer("radius").transform.rotation*-1

    thisComp.layer("radius").transform.rotation*-1.5-90

    John Burgess replied 4 years, 3 months ago 2 Members · 2 Replies
  • 2 Replies
  • Robert Müller

    June 3, 2020 at 1:32 pm

    Hi,
    this should work just fine, you need to access the global position of your guides. I made a setup parenting a small white circle on an outlined one, driven by the rotation:

    xC=thisComp.layer("x1c"); //small white circle 1; For the X value
    yC=thisComp.layer("y1c"); //small white circle 2; For the Y value
    x=xC.toComp(xC.anchorPoint)[0]; //getting the global X value
    y=yC.toComp(yC.anchorPoint)[1]; //getting the global Y value
    [x,y]

    I added this expression to the position of a null which then I can trace using Write-on or the plugin you linked.

  • John Burgess

    June 3, 2020 at 3:53 pm

    Hi Robert

    This worked perfectly, thank you so much.

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