Controlling 1 layers position by another layers rotation

[Kevin Camp]

you can use a the linear() function to try and interpret rotation as position. something like this as the position expression would move a layer as a the 3d ‘rotation layer’ turns on the x and y axis:

x = linear(thisComp.layer(“rotating layer”).transform.yRotation, -45, 45, 0, 720);
y = linear(thisComp.layer(“rotating layer”).transform.xRotation, -45, 45, 480, 0);
[x, y]

it takes the rotation values between 90 degrees (-45 – 45 = 90) and plots that value over a 0-720 px (the comp width) horizontally and 480-0 px vertically… you would like to know the camera’s viewing angle so you could use that to define the rotation — in my expression i arbitrarilly used 90, but if your veiwing anlg was 60, the values might be -30, 30.

using this will most likely require some trial and error to get values that will seem natural.

do you think you’d be better off using the 3d camera data on a 3d camera and position your layers in 3d space? you should get more realistic movement in you scene.

Kevin Camp
Designer – KCPQ, KMYQ & KRCW

[Gallion311]

do you think you’d be better off using the 3d camera data on a 3d camera and position your layers in 3d space? you should get more realistic movement in you scene.

Yeah, that was my first notion as well, but I’ve never been a fan of After Effects’ 3d stuff and I ran into a problem. I was compositing in a flat image as a matte painting background (some stormy clouds, a castle on a hill) but when the camera rotated (panned) in 3d, the flat background was heavily skewed due to the perspective offset. So it was evident that it was just a flat plane in 3d space. My other solution would be to create a makeshift cylinder, composed of 4 different flat planes…but I figured there may be a more optimal solution using a script to turn the 3d rotation into 2D movement.

As it turns out I did some more Googling, and there’s a set of scripts called MoCon for AE that help when importing/exporting cameras to and from AE.

http://www.3dmation.com

One of those scripts was called 3D to 2D which does excatly what I needed.

I’ll still play around with your script though becuase I always prefer having some understanding of what I’m doing rather that just clicking a button.