Write-on effect: coordinates not changing.

[dose0D45]

Hello!

I want to use the write-on effect on a robot-like arm that moves in circles, and i created the arm by parenting objects to each other. I then parented an object to the end of the arm and attached the write-on to this. So everything moves when I animate the rotation of the objects but the write-on is not writing. And I assume it's because the move-coordinates of the object on the end of the arm are not changing.

Does this make sense, and is there a way around this??

[Mylenium · Accepted solution]

You completely misunderstand. A Null is a non-rendering layer type to begin with and Write-On does not trace the layer motion. You need to apply the effect to a solid covering the entire comp and connect the effect's internal crosshair control with a pickwhip expression. In addition, however, you may need to use a layer space transform like toComp() and additional math to compensate for the positioning of the shape layer groups and the different coordinates used.

Mylenium

[dose0D45]

Hmm, ok! Yes, the null was a shot in the dark, i just wanted to find something that would change the position-coordinates as it was moved around by the arm so i could control the position of the write-on with that. And pardon my french here, I am indeed learning by doing. But of course, the write-on needs a solid to write on, makes sense 🙂 I will dig abit deeper based on your suggestions, thanks.

[dose0D45]

I guess my problem then is that the object i want to drive the position of the write-on crosshair doesn't change its position coordinates, and I guess that is because it's a child of another moving object and that the only animated values are rotate-values. Besides the now obvious reason that the write-on needs a solid covering the entire comp to write on 🙂

[dose0D45]

Seems like you nailed it, looking at some toComp tutorials now and it's exactly what I am looking for 🙂