Different results when keyframing visual transforms and applying transforms manually on IK constraint #76791

New Issue

Blender Version
Broken: v2.82a and blender-2.90-f9d0f59bed4d-windows64
Working: never, tested with 2.75a and that even shows this issue.

Short description of error
There is a difference between using the insert keyframe menu to insert Visual LocRot compared to if you Apply Visual Transform to Pose and then use normal keyframe LocRot.

Exact steps for others to reproduce the error

keyframe-visual-root.blend

Open the attached blend file.
Set a VisualLocRot keyframe on the root bone.
See in the graph editor that the orientation is keyed with quaternion (1, 0, 0, 0), even though the bone was visually influenced by the IK constraint.
Disable the IK constraint, and see that the root bone moves.

Using Keyframe Menu (broken):

2020-05-15 11-24-58.mkv

Iterating Keyframe Insertion (Semi-working):
2020-05-15 12-02-32.mkv

Manually applying transforms to Pose (working):

2020-05-15 11-29-47.mkv

**Blender Version** Broken: v2.82a and blender-2.90-f9d0f59bed4d-windows64 Working: never, tested with 2.75a and that even shows this issue. **Short description of error** There is a difference between using the insert keyframe menu to insert Visual LocRot compared to if you Apply Visual Transform to Pose and then use normal keyframe LocRot. **Exact steps for others to reproduce the error** [keyframe-visual-root.blend](https://archive.blender.org/developer/F8547898/keyframe-visual-root.blend) - Open the attached blend file. - Set a VisualLocRot keyframe on the root bone. - See in the graph editor that the orientation is keyed with quaternion (1, 0, 0, 0), even though the bone was visually influenced by the IK constraint. - Disable the IK constraint, and see that the root bone moves. --------------------------------- Using Keyframe Menu (broken): [2020-05-15 11-24-58.mkv](https://archive.blender.org/developer/F8537522/2020-05-15_11-24-58.mkv) Iterating Keyframe Insertion (Semi-working): [2020-05-15 12-02-32.mkv](https://archive.blender.org/developer/F8537574/2020-05-15_12-02-32.mkv) Manually applying transforms to Pose (working): [2020-05-15 11-29-47.mkv](https://archive.blender.org/developer/F8537534/2020-05-15_11-29-47.mkv)

Added subscriber: @sok0

#81302 was marked as duplicate of this issue

Added subscriber: @mano-wii

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

Could you provide a simple .blend file demonstrating the problem?
Also videos should be used to quickly describe the problem and not as steps to reproduce the problem.
A guideline for making a good bug report can be found at https://wiki.blender.org/wiki/Process/Bug_Reports

Could you provide a simple .blend file demonstrating the problem? Also videos should be used to quickly describe the problem and not as steps to reproduce the problem. A guideline for making a good bug report can be found at https://wiki.blender.org/wiki/Process/Bug_Reports

IK_constraint_keyframe.blend

Armature was keyframed with Visual LocRot
Armature.001 was keyframed after using Apply Visual Transform to Pose

Expected result should be the same. Instead the Visual LocRot does not properly keyframe the pose position of the IK constraint.

[IK_constraint_keyframe.blend](https://archive.blender.org/developer/F8543466/IK_constraint_keyframe.blend) Armature was keyframed with Visual LocRot Armature.001 was keyframed after using Apply Visual Transform to Pose Expected result should be the same. Instead the Visual LocRot does not properly keyframe the pose position of the IK constraint.

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

Added subscriber: @dr.sybren

@sok0 Please test with older versions of Blender to see which version of Blender still worked properly. This will help developers in finding the root cause of the issue.

For videos, please use h.264 in an MP4 container, so that they can be directly played back in the browser. Re-encoding them after the recording will make them much smaller (I have them stored at a 1/35th the file size on my machine after locally re-encoding them).

@sok0 Please test with [older versions of Blender](https://download.blender.org/release/) to see which version of Blender still worked properly. This will help developers in finding the root cause of the issue. For videos, please use h.264 in an MP4 container, so that they can be directly played back in the browser. Re-encoding them after the recording will make them much smaller (I have them stored at a 1/35th the file size on my machine after locally re-encoding them).

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

In #76791#936612, @dr.sybren wrote:
@sok0 Please test with older versions of Blender to see which version of Blender still worked properly. This will help developers in finding the root cause of the issue.

I tested with few older versions. As you go back in the versions it never seemed to work and at some point the Apply Visual Transform to Pose operation stops working as well so it's not possible to test further.

2.79b not working, same behavior
2.77a not working, same behavior
2.60 not working, apply pose as rest pose doesn't work either
Blender 2.5 doesn't work and apply pose as rest pose doesn't work either

For videos, please use h.264 in an MP4 container, so that they can be directly played back in the browser. Re-encoding them after the recording will make them much smaller (I have them stored at a 1/35th the file size on my machine after locally re-encoding them).

got it

> In #76791#936612, @dr.sybren wrote: > @sok0 Please test with [older versions of Blender](https://download.blender.org/release/) to see which version of Blender still worked properly. This will help developers in finding the root cause of the issue. I tested with few older versions. As you go back in the versions it never seemed to work and at some point the Apply Visual Transform to Pose operation stops working as well so it's not possible to test further. 2.79b not working, same behavior 2.77a not working, same behavior 2.60 not working, apply pose as rest pose doesn't work either Blender 2.5 doesn't work and apply pose as rest pose doesn't work either > > For videos, please use h.264 in an MP4 container, so that they can be directly played back in the browser. Re-encoding them after the recording will make them much smaller (I have them stored at a 1/35th the file size on my machine after locally re-encoding them). got it

@sok0 thanks for testing. I did some digging, and it's due to the way visual keying is implemented in Blender (visualkey_can_use() in keyframing.c). It will fall back to regular keying when there is no parent bone and no constraint on the bone either. This "no constraint" check does not consider IK-chains on child bones, which is why the root bone of the chain isn't keyed correctly. This has been pretty much been the situation since the code was ported to Blender 2.50 (6343d4e233) 11 years ago.

This can be resolved by simply always performing visual keying when a user chooses that from the keying set menu, regardless of whether there are any constraints. This would be a bigger change than is currently possible for Blender 2.83, though. First and foremost, this change in behaviour should be discussed with more animators, which I'll do.

@sok0 thanks for testing. I did some digging, and it's due to the way visual keying is implemented in Blender (`visualkey_can_use()` in `keyframing.c`). It will fall back to regular keying when there is no parent bone and no constraint on the bone either. This "no constraint" check does **not** consider IK-chains on child bones, which is why the root bone of the chain isn't keyed correctly. This has been pretty much been the situation since the code was ported to Blender 2.50 (6343d4e233) 11 years ago. This can be resolved by simply always performing visual keying when a user chooses that from the keying set menu, regardless of whether there are any constraints. This would be a bigger change than is currently possible for Blender 2.83, though. First and foremost, this change in behaviour should be discussed with more animators, which I'll do.

@sok0 Is visual keying part of your day-to-day workflow? Or is it just something you're trying out?

@dr.sybren I came across the bug on a side project to write my own IK solver algorithm and wanted to compare my results to what Blender produced. I was creating an animation for a robot arm and wanted to see what the difference would be between joint interpolated motion and Cartesian interpolated motion of the end effector. Joint interpolated motion required visual keying of the start and ending frame rotations of each joint while Cartesian interpolation used the IK constraint and only keyed the IK target then letting the IK solver calculate new joint rotations on every frame. When I was not getting the expected results for the joint interpolated motion I realized there might be a bug and traced it back to visual keying. Hopefully that answers the question, let me know if there is any other way I can help.

Added subscribers: @wbmoss_dev, @Hjalti, @BassamKurdali

The people I have talked with (@BassamKurdali , @Hjalti, @wbmoss_dev) have all expressed that they perceive Visual Keying as buggy, and that this is why they don't use it in their day-to-day workflow. It seems that Visual Keying, even though the idea looks nice, needs a redesign to become usable in practice.

As such, I'll mark this down as a known issue. In time we can create a design task and make this work properly.

The people I have talked with (@BassamKurdali , @Hjalti, @wbmoss_dev) have all expressed that they perceive Visual Keying as buggy, and that this is why they don't use it in their day-to-day workflow. It seems that Visual Keying, even though the idea looks nice, needs a redesign to become usable in practice. As such, I'll mark this down as a known issue. In time we can create a design task and make this work properly.

Added subscribers: @netricsa, @iss

Added subscriber: @0xb

was there a design task created for this? Just wondering how it's going.

@dr.sybren you mentioned above that the people you spoke with don't use visual keying. I'm wondering, what's the alternative if you're wanting to transition from IK to FK?

I'm using visual keying to key the position of the bones post IK constraints, so that when I disable the IK constraint the FK bones will remain in the same location. Really interested to know which alternative method is possible.

@dr.sybren you mentioned above that the people you spoke with don't use visual keying. I'm wondering, what's the alternative if you're wanting to transition from IK to FK? I'm using visual keying to key the position of the bones post IK constraints, so that when I disable the IK constraint the FK bones will remain in the same location. Really interested to know which alternative method is possible.

actually, I think I realise now they must be applying visual transform to pose and then inserting a standard keyframe (not visual), as I now understand that all 'apply visual transform to pose' does, is move the selected bones to the constrained position they're in, so that when you insert standard location rotation (not visual) keyrframes, the keyframes are created in the visual location. Very odd how keyframing this way works, but inserting a visual location rotation keyframe doesn't.

Perhaps instead of a full redesign (which appears to not be happening based on the 3 year elapsed time), just make inserting a visual location/rotation keyframe do the following:

apply visual transform to pose
insert standard location rotation keyframe.

actually, I think I realise now they must be applying visual transform to pose and then inserting a standard keyframe (not visual), as I now understand that all 'apply visual transform to pose' does, is move the selected bones to the constrained position they're in, so that when you insert standard location rotation (not visual) keyrframes, the keyframes are created in the visual location. Very odd how keyframing this way works, but inserting a visual location rotation keyframe doesn't. Perhaps instead of a full redesign (which appears to not be happening based on the 3 year elapsed time), just make inserting a visual location/rotation keyframe do the following: apply visual transform to pose insert standard location rotation keyframe.

Wow this has been around a while, and I am in agreement at least that I am not clear at all now on why/what visual keying is doing if it isn't applying the visual transform and keying that.
I think now is a good time to see if a small change can make this intuitive to use and we can update the documentation as well.

Wow this has been around a while, and I am in agreement at least that I am not clear at all now on why/what visual keying is doing if it isn't applying the visual transform and keying that. I think now is a good time to see if a small change can make this intuitive to use and we can update the documentation as well.

With what I said in my earlier comment in mind, this might be fairly doable to address for Blender 4.0.

With what I said in [my earlier comment](https://projects.blender.org/blender/blender/issues/76791#issuecomment-326910) in mind, this might be fairly doable to address for Blender 4.0.

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Different results when keyframing visual transforms and applying transforms manually on IK constraint #76791