Turbulent Displace a Null's position

Question

Hello,

We frequently import animated nulls from C4D into AE for adding labels. Our team likes adding Turbulent Displace to our renders, but obviously TD only works on pixel data - it doesn't displace/effect the position values of animated nulls - and thus the labels we create no longer 'stick' to the renders.

Is there any way to sample a turbulent displacement's effect and apply it to a 2D position via expression?

If not, is there some other way to ensure that the null object's position gets the same displacement so that it stays in lock step with the pixel data?

One possibility is performing a 2D track on the new, displaced visuals - but that isn't practical, as often times the objects being labeled don't have any real tracking points.

Another initial thought was placing the TD adjustment layer above the label layers, but then they look terrible and become hard to read.

As it stands, I have to manually track each label by hand/eye, but there's so much undulation in the image that it's nearly impossible to get it looking good in the time we have allotted for this part of production - and inevitably the labels just look drunk.

Thoughts?

Thanks,

Luke

Rick Gerard · Answer

Add a shape layer circle that is about 10 pixels in diameter with a 2-pixel contrasting stroke as a marker where you want each label positioned, then Pre-compose the layer(s) you are going to displace and the shape layer. Open the pre-comp, add turbulent displace to the adjustment layer, set the animation to what you want, then turn off the everything but the adjustment layer and the circle markers.

Back in the main comp motion track the markers. They. should be really easy to catch and hold onto, then attach the tracking data to the appropriate nulls.

Go back to the nested comp (Pre-comp) and turn off the shape layer with the markers and turn the rest of the layers back on.

Your Labels should now move with the displacement. If you want to add a little additional wiggle, precompose all the labels, copy the displacement effect in the Pre-comp and past it to the label pre-comp, add a full-frame mask to the pre-comped labels, enable compositing options using the mask, then adjust the mask opacity to limit the effect of the displacement and keep the labels readable.

If your imported nulls are moving you'll have to use parenting and additional nulls to keep them attached to the displaced layer.

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