keyframe interpolation "Elastic" always starts down on the Y-Axis #85433

New Issue

tt · 2021-02-06T18:55:27+01:00

tt commented

2021-02-06 18:55:27 +01:00

System Information
Operating system: Linux-5.4.0-65-generic-x86_64-with-debian-bullseye-sid 64 Bits
Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.102.04

Blender Version
Broken: version: 2.92.0 Beta, branch: master, commit date: 2021-01-31 13:31, hash: a9b53daf23
Worked: (newest version of Blender that worked as expected)

Short description of error
when having two keyframes and setting the interpolation of the first one to elastic the curve always goes down on the Y- Axis first.
This leads to having to add another keyframe like this:

Maybe I am missing something and this is not a bug, but setting the Amplitude of the elastic interpolation to a negative value is where I would flip that behaviour, but the amplitude is limited to positive values only. Allowing negative values for the amplitude would fix this.

Exact steps for others to reproduce the error
Add 2 keyframes to cube, set interpolation of the first keframe to elastic, try to flip the elastic curve to start upwards bound on the Y-Axis...

**System Information** Operating system: Linux-5.4.0-65-generic-x86_64-with-debian-bullseye-sid 64 Bits Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.102.04 **Blender Version** Broken: version: 2.92.0 Beta, branch: master, commit date: 2021-01-31 13:31, hash: `a9b53daf23` Worked: (newest version of Blender that worked as expected) **Short description of error** when having two keyframes and setting the interpolation of the first one to elastic the curve always goes down on the Y- Axis first. This leads to having to add another keyframe like this: ![grapheditor elastic.jpg](https://archive.blender.org/developer/F9674300/grapheditor_elastic.jpg) Maybe I am missing something and this is not a bug, but setting the Amplitude of the elastic interpolation to a negative value is where I would flip that behaviour, but the amplitude is limited to positive values only. Allowing negative values for the amplitude would fix this. **Exact steps for others to reproduce the error** Add 2 keyframes to cube, set interpolation of the first keframe to elastic, try to flip the elastic curve to start upwards bound on the Y-Axis...

tt commented

2021-02-06 18:55:27 +01:00

Added subscriber: @ToxicTuba

Falk David commented

2021-02-09 12:19:25 +01:00

Added subscriber: @filedescriptor

Falk David commented

2021-02-09 12:19:25 +01:00

I believe what you want to adjust is the Period. If you just flip the sign it will flip the direction.

I believe what you want to adjust is the *Period*. If you just flip the sign it will flip the direction. ![image.png](https://archive.blender.org/developer/F9748198/image.png) ![image.png](https://archive.blender.org/developer/F9748208/image.png)

Falk David commented

2021-02-09 12:20:01 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

tt commented

2021-02-12 15:22:44 +01:00

indeed this solves this issue. Somehow I figured it has to be the amplitude that needs to be flipped, scaling down the period seems counter intuitive, as in my mind it would flip the curve along the x axis and the elastic interpolation always starts at the keyframe and goes on to the right and there is nothing to the left of it where that flipped period would appear in a maths graph when manipulating the x expansion, but in a keyframe editor it kind of makes sense...
scaling the amplitude seemed more intuitive as it was manipulating the y axis already... can't we have negative values on both amplitude and period?

indeed this solves this issue. Somehow I figured it has to be the amplitude that needs to be flipped, scaling down the period seems counter intuitive, as in my mind it would flip the curve along the x axis and the elastic interpolation always starts at the keyframe and goes on to the right and there is nothing to the left of it where that flipped period would appear in a maths graph when manipulating the x expansion, but in a keyframe editor it kind of makes sense... scaling the amplitude seemed more intuitive as it was manipulating the y axis already... can't we have negative values on both amplitude and period?

Falk David commented

2021-02-12 15:40:28 +01:00

Changed status from 'Needs User Info' to: 'Archived'

Falk David closed this issue

2021-02-12 15:40:28 +01:00

Falk David commented

2021-02-12 15:40:28 +01:00

I am not sure about the negative amplitude. Usually, it's an absolute value. "The amplitude is the amount of the maximum deflection in the 𝑦 direction". This would have to be discussed with the UI team.

Closing this for now since it's not a bug.

I am not sure about the negative amplitude. Usually, it's an absolute value. "The amplitude is the amount of the maximum deflection in the 𝑦 direction". This would have to be discussed with the UI team. Closing this for now since it's not a bug.

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keyframe interpolation "Elastic" always starts down on the Y-Axis #85433