tracing the path of cardiods...? (with video example)

[AngeloL]

Hello friends,

So I have some shapes parented to each other and animated, and there is a shape layer that animates depending on the rotation parameters of the parents rotation. I have the echo effect applied to this target shape layer which creates interesting cardiod "paths"

My question is; how do I trace the path of the cardiod with a solid, unbroken line, instead of the "dotted" line that I am creating with the echo effect? Thanks!

example on Vimeo

[Wim_Schalley]

Hi,

I always use a particle generator for these kinds of effects; in my case Particular. But CC Particle Systems II works as well, albeit not as pretty 🙂

Look at the screenshot here, it's an example with keyframed motion, but you can add an expression to the Producer's 'Position' parameter to connect it to the moving shape layer in your animation.

Play around with the parameters; 'longevity' creates a longer trace, 'opacity map' gives it a nice fade at the end of the trace.

Wim

[AngeloL]

Thanks Wim! I understood what you mean up to a point... I got the particle generator to trace along an animated path, but I run into trouble when I want it to move along the cardioid path, because the shape (tiny circle) that is the beginning tracer for the cardiod doesn't actually change any position parameters, since it is just the great great grandchild of one rotating shape layer. The blue dotted line is that shape layer with the echo effect on it for illustration. Could I write an expression to have the particle solid layer trace along the "blue circle" layer, even though the blue circle layer isn't moving? How could I write that expression? Thank you!!!

[Roland Kahlenberg · Accepted solution]

I suggest you use the Effect>Generate>Write-on to create the line instead of Echo or a Particle System.

Apply this Expression to Write-on's Brush Position prop -

-----------------------------------------------------

c=thisComp.layer("Child_Layer");

c.toComp(c.anchorPoint)

-----------------------------------------------------

Ensure you change the layer name in line 1, above.

[AngeloL]

That's what I was looking for. Thank you.