Rotating a bulge around a null object

[TheNomadicAspie]

I have a magnifying glass object that I move in a circle without rotating by parenting the magnifying glass to a null object, rotating the null object, and using an expression to counter the rotation like in this guide:

https://www.youtube.com/watch?v=5eHeiqzAL3A&ab_channel=Francis.JMotionDesigner

I have a bulge effect I'm applying to a background layer and I need the bulge to follow the magnifying glass around to simulate looking through it. Here's a pic to show what I mean.

Methods online show to drag the pick whip of bulge center to the position of the null object. But since the null object rotates and doesn't have any position keys, doing that just causes the bulge to center in the top-left corner of the screen and not move.

Any ideas for how I can get the bulge effect to follow this magnifying glass as it rotates around a null object?

[Rick Gerard]

I am not sure that I completely understand your workflow. I think you want to rotate the magnifying glass graphic, the null that is showing is not in the center of the magnifying glass, but I think that is the center of rotation.

To attach the Center of the Bulge effect to the Center of the Magnifying glass you have to move the anchor point of the Magnifying Glass layer to the center of the lens. It will still rotate around the null.

Then you have to use layer space transformations in an expression to get the comp position of the center of the magnifying glass layer and apply it to the Bulge effect. If you had included a screenshot that shows us the modified properties (press 'uu') of your layers I would know for sure. This is what that would look like, and I would probably use Magnify instead of Bulge, but here goes:

Here is the expression:

L = thisComp.layer("Magnifying Glass");
L.toComp(anchorPoint)

I even uploaded an AEP file for you to look at.  

[TheNomadicAspie2]

Sorry I don't think I explained what I'm doing very clearly. Since the last post I made an adjustment layer and parented it to get the effect I'm looking for, which is this:

https://streamable.com/tnfh1y

The only thing wrong now is that the background image rotates with it, and I want the text to be right-side up but for the rest of the animation to stay the same.

I have an expression on magnifying_glass that counters the rotation, but if I apply that to the mask as well, this happens:

https://streamable.com/39wxll

This is my composition right now pressing uu:

https://imgur.com/a/2kEabZJ

I appreciate you taking the time to help me, but I'm trying to keep the handle at the same degree while it rotates. I should have mentioned that.

[TheNomadicAspie2]

I also just realized in that video the background is static when I'm trying to create a transparent/xray effect where you can see the background layer behind the head only where the magnifying glass is.

I can't figure out how to Google that though...

[Mylenium]

You are over-complicating this and are forgetting/ ignoring that effects operate relative to the layer, not the comp. the coordinates from your rotating glass would need to be converted using layer space transforms such as toComp(). The circle can easily be created using the effect of same name instead of a mask. Simply set the rendering mode in the effect to Stencil Alpha. Avoids another step off coordinate conversions. Other than that you simply may want to reconsider your setup. If you really want to "rotate" your magnifier glass around an imaginary center copy & pasting a suitably sized mask path top the position property after you created it on a matching comp-sized solid might have been a more beginner-friendly approach rather than putting up with this rotation stuff. Then you wouldn't need extra math to counter the rotation and your simple pickwhip stuff would work right away. Either way, it might be a good idea to read the online help and find some good tutorials on some of these basics.

Mylenium