Changing extrapolation in graph editor modifies the tangents. #79804

New Issue

Robert Rioux · 2020-08-15T14:57:37+02:00

Robert Rioux commented

2020-08-15 14:57:37 +02:00

System Information
Operating system: Darwin-16.7.0-x86_64-i386-64bit 64 Bits
Graphics card: NVIDIA GeForce GTX 980 OpenGL Engine NVIDIA Corporation 4.1 NVIDIA-10.18.5 378.05.05.25f19

Blender Version
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-08 15:55, hash: 9f7d84b656
Worked: (newest version of Blender that worked as expected)

Short description of error
Changing extrapolation in graph editor modifies the tangents.

Exact steps for others to reproduce the error
See attached image.

**System Information** Operating system: Darwin-16.7.0-x86_64-i386-64bit 64 Bits Graphics card: NVIDIA GeForce GTX 980 OpenGL Engine NVIDIA Corporation 4.1 NVIDIA-10.18.5 378.05.05.25f19 **Blender Version** Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-08 15:55, hash: `9f7d84b656` Worked: (newest version of Blender that worked as expected) **Short description of error** Changing extrapolation in graph editor modifies the tangents. **Exact steps for others to reproduce the error** See attached image.![Screen Shot 2020-08-15 at 8.48.21 AM.png](https://archive.blender.org/developer/F8783512/Screen_Shot_2020-08-15_at_8.48.21_AM.png)

Robert Rioux commented

2020-08-15 14:57:37 +02:00

Added subscriber: @Funnybob

Richard Antalik commented

2020-08-19 02:22:26 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-08-19 02:22:26 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Richard Antalik closed this issue

2020-08-19 02:22:26 +02:00

Richard Antalik self-assigned this 2020-08-19 02:22:26 +02:00

Richard Antalik commented

2020-08-19 02:22:26 +02:00

This is working as designed, see https://docs.blender.org/manual/en/dev/editors/graph_editor/fcurves/introduction.html#extrapolation-mode

Thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors.

For user requests and feedback, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests
For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

This is working as designed, see https://docs.blender.org/manual/en/dev/editors/graph_editor/fcurves/introduction.html#extrapolation-mode Thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors. For user requests and feedback, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

Robert Rioux commented

2020-08-19 05:43:36 +02:00

Hi,

No offense but when a tool doesn’t do what it’s supposed to do, that’s a bug. Here, it’s supposed to extrapolate the curves. That means keeping the tangents the way the are and extend them to infinity. This is not what’s going on. It screws up the animation curves and gives you a totally wrong result. Again, the tangents should not be modified at all when calling the function. The documentation is wrong as the example doesn't show what happens in the case I showed in my example. I gave you a picture to show you that it's broken. I would ask you to please reconsider.

Cheers,

Robert

Hi, No offense but when a tool doesn’t do what it’s supposed to do, that’s a bug. Here, it’s supposed to extrapolate the curves. That means keeping the tangents the way the are and extend them to infinity. This is not what’s going on. It screws up the animation curves and gives you a totally wrong result. Again, the tangents should not be modified at all when calling the function. The documentation is wrong as the example doesn't show what happens in the case I showed in my example. I gave you a picture to show you that it's broken. I would ask you to please reconsider. Cheers, Robert

Richard Antalik commented

2020-08-20 00:49:32 +02:00

In #79804#998448, @Funnybob wrote:
Hi,

No offense but when a tool doesn’t do what it’s supposed to do, that’s a bug. Here, it’s supposed to extrapolate the curves. That means keeping the tangents the way the are and extend them to infinity. This is not what’s going on. It screws up the animation curves and gives you a totally wrong result. Again, the tangents should not be modified at all when calling the function. The documentation is wrong as the example doesn't show what happens in the case I showed in my example. I gave you a picture to show you that it's broken. I would ask you to please reconsider.

Cheers,

Robert

I understand your point, and I can agree that it would be nice if you can apply interpolation on only "one side" of curve. But this is not how this feature was intended to work. Your request is not bad, but it doesn't belong to this tracker. Please use following link to request such feature https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

> In #79804#998448, @Funnybob wrote: > Hi, > > No offense but when a tool doesn’t do what it’s supposed to do, that’s a bug. Here, it’s supposed to extrapolate the curves. That means keeping the tangents the way the are and extend them to infinity. This is not what’s going on. It screws up the animation curves and gives you a totally wrong result. Again, the tangents should not be modified at all when calling the function. The documentation is wrong as the example doesn't show what happens in the case I showed in my example. I gave you a picture to show you that it's broken. I would ask you to please reconsider. > > Cheers, > > Robert I understand your point, and I can agree that it would be nice if you can apply interpolation on only "one side" of curve. But this is not how this feature was intended to work. Your request is not bad, but it doesn't belong to this tracker. Please use following link to request such feature https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

Robert Rioux commented

2020-08-20 13:51:39 +02:00

You told me to read the documentation. This is what it says:

Curves ends are straight lines (linear),as defined by the slope of their first and last keyframes.

And that's exactly my point. In the example I gave you on the attached picture, the first tangent is horizontal. So when you extrapolate, the tangent SHOULD stay horizontal but the function breaks the original animation by changing the slope between the first and last keyframes. Only the parts before and after the first keyframe should be modified. It works for the second keyframe but not for the first one. Please get a second opinion on this.

As for being able to apply it only on one side, yes, that would be great, actually a must for an animator. In Maya, it's called infinity before and infinity after.

You told me to read the documentation. This is what it says: Curves ends are straight lines (linear),**as defined by the slope of their first and last keyframes**. And that's exactly my point. In the example I gave you on the attached picture, **the first tangent is horizontal.** So when you extrapolate, the tangent **SHOULD stay horizontal** but the function **breaks the original animation by changing the slope *between* the first and last keyframes**. Only the parts before and after the first keyframe should be modified. It works for the second keyframe but not for the first one. Please get a second opinion on this. As for being able to apply it only on one side, yes, that would be great, actually a must for an animator. In Maya, it's called infinity before and infinity after.

Richard Antalik commented

2020-08-21 03:16:05 +02:00

I have looked in the code to see how this works - Blender considers handles to be automatically updated when changing extrapolation, unless you touch them (change type, angle or even scale by 1, so no change really). After handle is changed manually it won't be updated automatically.

So this is obviously by design and it is quite baked in. I wasn't really able to override this behavior in a way that would be acceptable. Otherwise I would post patch so we can consider change.

I have looked in the code to see how this works - Blender considers handles to be automatically updated when changing extrapolation, unless you touch them (change type, angle or even scale by 1, so no change really). After handle is changed manually it won't be updated automatically. So this is obviously by design and it is quite baked in. I wasn't really able to override this behavior in a way that would be acceptable. Otherwise I would post patch so we can consider change.

Robert Rioux commented

2020-08-22 15:20:30 +02:00

Yeah, I see what you mean. So if you make keyframes but don't modify the handles at least once, the function doesn't work properly but if you do make a change, then it's ok. Well, now I have a workaround. Thanks Richard for taking the time to figure it out. Your help is appreciated. Cheer.

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Changing extrapolation in graph editor modifies the tangents. #79804