Object bouncing despite keyframes dictating it should travel directly from Point A to Point B

[Shaun M]

Looking for help!  Currently running After Effects (17.1.3) on a 2019 iMac.  In a comp of mine dynamically linked to Premiere Pro, I have a photo parented to a solid rectangle that is supposed to quickly enter the frame from below, slow to a crawl (still moving straight upward) for two seconds, and then quickly accelerate (upward) again to exit the frame.  The keyframe that separates the quick entrance from the beginning of the crawl (We'll call this Point A) is set to 'Easy Ease In' and the keyframe after it that separates the crawl from the quick exit (We'll call this Point B) is set to 'Easy Ease Out.'  For some reason during the slow crawl, rather than travel directly from Point A to Point B at a constant speed, the photo/rectangle leaves Point A, backtracks (reverses) suddenly for an instant, and then continues forth again toward Point B.  Between the keyframes (Point A and Point B) on the graph, accurately mirroring this, the objects' y-coordinate rises linearly for a third of the way, decreases linearly for the next third, and then rises linearly again for the final third.  Thinking I could 'straighten the curve' in graphical view, I highlighted both keyframes and under Keyframe Interpolation, selected 'Linear,' however, that seemed to do nothing.  I tried all other interpolations, as well.  I also tried deleting and re-setting all keyframes on the parent (photo) layer.  Quiting and re-launching After Effects does not rectify my problem either.  I have a second photo/rectangle that simultaneously enters and exits on the other side of the frame and its pathway/behaviour is fine (There is a straight line between its Point A and B keyframes).  Can anyone suggest why this is happening and what I could try to fix it? 

Thanks in advance for any advice!

[Andrew Yoole]

As a matter of forum housekeeping, it's much easier to view reference images in context if you embed them in your post as an image, rather than add them as a link.  And try not to crop if unnecessary, it's better if we can see the whole window.

Your cropped screengrab appears to show that you are looking at the graph of X position values only, which doesn't tell you or us what the Y position is doing. My guess is the Y position is doing something weird.  Can you re-post a screengrab of the entire timeline and preview panes?

[Shaun M]

Thank you, Andrew.  I'm new to this, so I appreciate the tips!

[Rick Gerard · Accepted solution]

Position, the bounce, is easiest to fix in the comp panel using the pen tool, and timing is adjusted with the speed graph. It is almost impossible to correct position errors using the graph editor. Easy Ease, in fact, all of the easing functions and keyframe interpolation adjust speed, not position. 

What you want to do is have your motion path visible in the comp panel and then use the pen tool to adjust the motion and get rid of bezier handles. You can adjust the paths easily and if you look carefully you'll see a little loop in the motion path that is causing your bounce. When you get the motion path the way you want it all you have to do is apply easy ease and then use the graph editor to fine-tune the acceleration between frames. 

This quick tutorial I a while ago should help you straighten things out. 

[Shaun M]

Thanks Rick.  I followed your advice and watched the video but for some reason couldn't grab the bezier handles to manipulate them.  Deleted them and recreating the pathway didn't seem to solve the problem, either.  In the end, some random 'frustration clicking' seemed to somehow do it and I was able to select and delete the node that was causing all the problems in the pathway.

[Ro Hackett]

If there is random movement between two keyframes like this I thought it was usually (spatial interpolation)

- select both the keyframes - right click on one -  select keyframe interpolation - spatial interpolation and set it to linear?

🤔

[HouHouHou · Accepted solution]

Ro, you saved me on this! And there is a default setting for it...

Settings > General > Default Spatial Interpolation to Linear.