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# Resizable Box with Object attached to the edges - How?

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 Resizable Box with Object attached to the edges - How? on May 4, 2018 at 4:57:31 pm

Hi,

I did search the forum for a solution to my problem and found one similar topic but it didn't work out for me. So I hope maybe someone can help me.
Here is what I want to achieve. (I dont know if this is the right way to post a picture)

I have a trapeze shape (not a shape layer actually) and I want two shapes to be attached to the trapeze. One at the left end and one at the right end. Now I want to adjust the size of the trapeze with a slider control.
BUT I don't want the angle of the trapeze to change. And I want the two other objects to stay connected to the left/right end of it.

I tried to make a tracking matte and control its position with the slider control but that doesn't work for several reasons. Is there a smart solution to this problem that you guys know?

And related to this subject I got another question. In case my picture that I tried to put into this post isn't visible, I try to explain as good as I can.
There is a small circle (red in the picture). This circle is moving randomly. And I want the trapeze to scale from 0 to 100 %. But it is supposed to start the scaling from the center of the circle. So it seems like it comes out of the circle.
Is there a way to make a layer connected to the position of another object just for one keyframe?
I cannot parent the two layers completely because when the trapeze has reached 100% size I want to change the position according to the background manually.

I hope I made myself reasonably clear. I'm not a native english speaker and apologize for any nonsense I may have written.

Thanks

 Re: Resizable Box with Object attached to the edges - How?on May 4, 2018 at 5:23:20 pm

The simplest is to make all shapes children of a null and scale the null. You can do an inverse scale on the squares if you want them to stay a constant size as their parent scales down.

or

If your trapezoid has perfectly flat tops and bottoms (the y position of the left top point is the same as the y position of the right top point) you could just get the values of the mask shape in the mask attributes and those four "positions" would be the x and y's of the extreme top right and extreme bottom left corners. An expression using those values would always position your squares at those comers. You could then alter the anchor of each square so that it "centers" the way you want it.. This would not work if you wanted the squares at the other corners.

or

If you are using AE2017 or later you could convert the mask path to nulls and scale the converted path and mask at the same time. Parent the nulls to the squares and the squares will follow along as the points of that path move as they are scaled. (converting the path to nulls is near the bottom of the windows menu - "Create nulls from path". Choose the "nulls follow points" option.

 Re: Resizable Box with Object attached to the edges - How?on May 7, 2018 at 5:19:18 pm

The third suggestion was exactly what I needed. So simple and so flexible.
I will use this feature a lot in the future. Can't believe I didn't know about that before.

Thanks a lot. Also for the other suggestions. You really helped me.

Greetings
Julia