Maniphest T76924

Animation Objects Move at Different Rates
Closed, Archived
Actions

Assigned To
Alaska (Alaska)
Authored By
James R. Manchester (xjmanchester)
May 20 2020, 8:32 PM
Tags
  • BF Blender
Subscribers
Alaska (Alaska)
James R. Manchester (xjmanchester)

Description

System Information
Operating system: Windows 10 Build 18363.778
Graphics card: NVIDIA GeForce RTX 2060 SUPER Version 442.92

Blender Version
Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen)
Worked: (newest version of Blender that worked as expected)

Short description of error
When playing back the timeline from 0 to 170, the objects should move upward at the same speed but they don't which can be seen by watching the orange object at the top (Weight). When the timeline gets to 170, everything is back in sync. This is a follow on to bug report T76885.

Exact steps for others to reproduce the error
Press the play button and watch the weight. It (and others) move at a different rate. You can see this by watching the magnet at the top. By the time the timeline is at 90, the magnet has almost disappeared. When it finally gets to 170, it's where it should be. If you delete the keyframes at location 190 and replay the timeline, everything works correctly. Somehow the keyframes at 190 are influencing the process between 0 and 170. As you can see, none of the other objects have keyframes between 0 and 170 so they can't be influencing the motion that way. Everything should move at the same rate between 0 and 170.

test.blend206 KBDownload

Based on the default startup or an attached .blend file (as simple as possible).

Related Objects

Event Timeline

James R. Manchester (xjmanchester) created this task.May 20 2020, 8:32 PM
Alaska (Alaska) closed this task as Archived.May 21 2020, 5:41 AM
Alaska (Alaska) claimed this task.
Alaska (Alaska) added a subscriber: Alaska (Alaska).

I am able to reproduce the issue you're describing, however I do not consider a bug and have closed the report. Here's why:

In Blender, each keyframe has what's know as "Handles" (They can be found in the graph editor). Handles control the rate of acceleration and deceleration between keyframes. By default, a keyframe will have the handle type "Automatic" which means it automatically changes to produce smooth motion as new keyframes are added to an object. The issue you're experiencing is that the keyframe you add at frame 190 is causing the handles on the previous two keyframes to change to produce smooth motion, but as a result the motion doesn't match other objects.

You can manually play around with the handles in the graph editor to try and fix your issue or change the types of handles used (E.G. Linear). Sadly I can't give you much advice as I don't know what the exact result you want in your scene.

For help with handles, please refer to the Blender manual or ask for help on the Blender community sites.

Note: Some information in the manual may be out dated. I, and other users, are in the process of updating it. However, most of the principals should be the same.