Maniphest T76928

FBX exporter doesn't export Constant Interpolation keyframes
Confirmed, NormalKNOWN ISSUE
Actions

Assigned To
None
Authored By
Justin Jensen (neverhood311)
May 21 2020, 12:53 AM
Tags
  • Add-ons (BF-Blender)
  • Import/Export
Subscribers
Dalai Felinto (dfelinto)
David Nunes (AlphaEndgame)
Germano Cavalcante (mano-wii)
Justin Jensen (neverhood311)
Petr (Petr)
Philipp Oeser (lichtwerk)
Pratik Borhade (PratikPB2123)
Richard Antalik (ISS)

Description

System Information
Operating system: Windows 10 Pro
Graphics card: NVidia Quadro M1200

Blender Version
Broken: 2.82a

Short description of error
The FBX exporter does not export Constant Interpolation keyframes. Instead, they're converted to Linear Interpolation

Exact steps for others to reproduce the error
Open the default scene.
Add a few location keyframes to the cube
Change each keyframe's interpolation type to Constant
Export as FBX
Import into Unity or back into Blender. The keyframes now have Linear Interpolation

Related Objects

Mentioned In
T94855: Key Interpolation bug
T68575: FBX Known issues & TODO's
Mentioned Here
rBA96a51679699c: FBX Exporter: Support special case of constant interpolation

Event Timeline

Justin Jensen (neverhood311) created this task.May 21 2020, 12:53 AM
Germano Cavalcante (mano-wii) added a subscriber: Germano Cavalcante (mano-wii).May 21 2020, 10:53 PM

Could you provide a simple file showing the problem?

Justin Jensen (neverhood311) added a comment.May 22 2020, 5:54 AM

simple_constant_interpolation_example.blend643 KBDownload

simple_constant_interpolation_example.fbx20 KBDownload

I've attached two files:
The first is a .blend file with an extremely simple animation. I want the cube to jump to the right on frame 20, then back to the origin on frame 40. No interpolation.
The second file is this cube exported to FBX. Upon first inspection, it kind of looks like the keyframes use Constant interpolation, but it's actually just two keyframes on adjacent frames with linear interpolation between them. This is a problem when I bring this 24fps animation into a 60fps application like Unity.

Richard Antalik (ISS) added subscribers: Dalai Felinto (dfelinto), Richard Antalik (ISS).May 25 2020, 1:05 AM

This looks like a limitation of exporting script. By doing some search for this I have found rBA96a51679699c implementing this feature but it has been reverted. I am not familiar with fbx format, so I can't see immediately what the issue was.

It's not clear to me if you wanted to have a go at implementing this. If you do, you can discuss possible solutions on https://devtalk.blender.org or ask @Dalai Felinto (dfelinto) on https://blender.chat/channel/blender-coders

Otherwise we could consider this a known issue or close as accidental feature request.

Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Confirmed.Jun 23 2020, 12:09 PM
Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Known Issue".
Philipp Oeser (lichtwerk) edited projects, added Add-ons (BF-Blender), Import/Export; removed BF Blender.
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).

If @Dalai Felinto (dfelinto) was already on it, I'd say we keep as Known Issue.
quoting from the commit message:

I need to tackle this differently.

Bastien Montagne (mont29) mentioned this in T68575: FBX Known issues & TODO's.Jul 28 2020, 11:20 AM
Bastien Montagne (mont29) moved this task from Backlog to Long Term on the Add-ons (BF-Blender) board.
David Nunes (AlphaEndgame) added a subscriber: David Nunes (AlphaEndgame).Oct 15 2020, 4:49 PM
This comment was removed by David Nunes (AlphaEndgame).
Pratik Borhade (PratikPB2123) mentioned this in T94855: Key Interpolation bug.Jan 13 2022, 7:50 AM
Pratik Borhade (PratikPB2123) merged a task: T94855: Key Interpolation bug.
Pratik Borhade (PratikPB2123) added subscribers: Petr (Petr), Pratik Borhade (PratikPB2123).