Drifting object between 2 keypoints

[Owen 01]

I have one object that follows a shape path, then is stationary for 2 minutes, then follows a different shape path. Either side of the stationary period are keyframes for position that are identical. However, the object very slowly drifts up 50 pixels and back down during the stationary period. The strange movement is also present after it is exported and processed by Media Encoder. This object covers a different animated object several times on another layer throughout the 2 minute period, so the shift is quite noticeable.

I have ensured that there is no other animation happening to the object in question, motion blur is off, and the anchor point does not change. What else should I check?

[Towerguy · Accepted solution]

Hi, it sounds like the boomerang effect.

https://www.youtube.com/watch?v=rLdBTzkMa7k

[Owen 01]

Thanks, Towerguy. Nice video an explanation.

My issue was a bit different because the two animations were separated by 2 minutes. I closely looked at the 2 keyframes at the ends of the paths adjacent to the 2 minutes of no movement, and ensured that all connecting keyframes had the same Y coordinate. I did this on one side by creating a duplicate keyframe 1 frame into the 2 minutes. It lowered the deflection from 50 pixels to 5. I can live with that.

But you lead me to look very closely at paths. And learn a bit more! Now I will wonder why mask paths must be bezier.

G'day!

[Martin_Ritter]

Mark both keyframes, right click, go to interpolate options and select "linear" on all dropdowns. That's just a misconfigured bezier interpolation (can happen when easing is involved). 

One tip: if you see it it in AE, it will be in the final file. Rendering it through AME won't solve this.

*Martin