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Object with follow-path constraint jumps off path, continuing slightly displaced.
Confirmed, NormalPublicKNOWN ISSUE

Description

Operating system: Linux, Debian 10 (Buster)
Graphics card: Secret (970)

Broken: (example: 2.81 alpha, 2019-08-09 a571ff2c16c6, master as found on the splash screen)
Worked: Unsure

Empty leaps off path.

Load attached blend. Move forward about 12 or so frames and you'll see the Empty jump off the path a bit. Increasing the curve resolution draws it increasingly closer to the visible path.

Event Timeline

Jaggz H (jaggz) renamed this task from Object with follo-path constraint chooses the path less traveled by. to Object with follow-path constraint chooses the path less traveled by..Aug 11 2019, 11:29 AM
Jaggz H (jaggz) created this task.
Jaggz H (jaggz) added a comment.EditedAug 11 2019, 11:39 AM

Oh, please note that I also keyed the Offset on the Empties (and set Fixed Position).

...and here's a video of it, for those who want to experience it without fiddling with a .blend.

https://www.youtube.com/watch?v=GreYnA4CWVo

Jaggz H (jaggz) renamed this task from Object with follow-path constraint chooses the path less traveled by. to Object with follow-path constraint jumps off path, continuing slightly displaced..Aug 12 2019, 3:12 AM
Jaggz H (jaggz) updated the task description. (Show Details)
Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Dec 30 2019, 1:49 PM

I can confirm the problem.
I believe the problem is in where_on_path.
Apparently the factor is calculated as if each segment of the curve had an equivalent length.
https://developer.blender.org/diffusion/B/browse/master/source/blender/blenkernel/intern/anim.c$461

Sybren A. Stüvel (sybren) changed the subtype of this task from "Report" to "Known Issue".Jan 14 2020, 2:55 PM

This is very old code, so Blender has been working like this for a long time. It would be nice to properly fix it at some point, but at this moment it's a Known Issue.