UE 5.7.1 Morph Target failure, possible regression

General Issues and Bug Reporting
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1

Summary

Morph targets fail to return to 0.0 in sequencer, skeletal mesh editor, and rendering. When in sequencer and rendering, this is very noticeable with eyes blinking. I set the first key frame to 0.0 (eyes open), next key frame is 1.0 (eyes closed), then the last key frame is back to 0.0. The character often shown about a 0.2 or 0.3 value even though the UI is set to 0.0. In the render, the first part looks normal.

After the eyes close, they won’t return to fully open. They look partially closed around a value of 0.2-0.3. In the skeletal mesh editor, I move the slider to 1, click the box to return it to 0, but the mesh retains the 1 value even though the value displays 0.0. This goes away when the slider is moved.

This was all normal for me in UE 5.6.

When in sequencer and rendering, this is very noticeable with eyes blinking.

I set the first key frame to 0.0 (eyes open), next key frame is 1.0 (eyes closed), then the last key frame is back to 0.0. The character often shown about a 0.2 or 0.3 value even though the UI is set to 0.0. In the render, the first part looks normal. After the eyes close, they won’t return to fully open. They look partially closed around a value of 0.2-0.3. In the skeletal mesh editor, I move the slider to 1, click the box to return it to 0, but the mesh retains the 1 value even though the value displays 0.0. This goes away when the slider is moved. This was all normal for me in UE 5.6.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

Character

Steps to Reproduce

  1. Open a skeletal mesh with morph targets (example: eye blink) in UE 5.7 or 5.7.1.

  2. In Sequencer, add a morph target track.

  3. Set keyframes:

Frame 1: morph value = 0.0 (eyes open)

Frame 2: morph value = 1.0 (eyes closed)

Frame 3: morph value = 0.0 (eyes open)

  1. Play the sequence in Sequencer.

  2. Render the sequence.

  3. Open the same skeletal mesh in the Skeletal Mesh Editor.

  4. Move a morph slider to 1.0, then click the checkbox/reset to return it to 0.0.

Expected Result

Morph targets should fully return to 0.0 when keyed or reset.

Eyes should return to fully open after blinking.

Skeletal mesh appearance should match the displayed morph value.

Behavior should match UE 5.6, where morph targets reliably clear back to zero.

Observed Result

Morph targets often do not visually return to 0.0 even though the UI shows 0.0.

In Sequencer and renders, eyes remain partially closed, approximately 0.2–0.3.

In renders, the first blink looks correct, but after closing once, the eyes do not fully reopen.

In the Skeletal Mesh Editor, resetting a morph from 1.0 back to 0.0 leaves the mesh visually deformed until the slider is moved again.

This behavior does not occur in UE 5.6 using the same assets.

Platform(s)

Windows 11, UE 5.7.1

Video

Additional Notes

@comlys

2

Can you try and disable the Morph Target Editing plugin and/or Skeletal Mesh Editor plugin?

3

Both of those plugins are disabled, and were never enabled.

4

Any update on this? I have this problem as well, 5.6 was fine, but in 5.7 I also have character blinking stuck sometimes, but seems happen randomly. Sometimes happen, sometimes it doesn’t. More often in low fps I noticed.

Then I think I able to solve it by setting my Morph target blinking, instead of 0.0→1.0 I interp the value 0.0→0.995 or something, not sure why it works though, but I haven’t see my character stuck at blinking again..

..Until today, I tried to bake SkeletalMesh with MorphTarget to StaticMesh, in SkeletalMesh Editor all MorphTarget is Working, but the resulted baked StaticMesh is doesn’t have any MorphTarget enabled at all.

EDIT: Baking SkeletalMesh with MorphTarget could still work in some mesh, but only happen to one SkeletalMesh, while other of my SkeletalMesh doesn’t work, not sure what differences, all SKM is imported from same Blender file.

This workflow (baking SkeletalMesh with MorphTarget to StaticMesh) was also working fine in back in 5.6.

Steps to reproduce:

  1. Open SkeletalMesh with MorphTarget
  2. Apply Morph Target for example Blinking from 0.0→1.0
  3. Apply pose/animation first frame (optional), it also happen without any pose applied
  4. Bake to StaticMesh using “Make Static Mesh”
  5. Open resulted StaticMesh, the MorphTarget isn’t applied

I think it’s related with how 5.7 working with MorphTarget somehow?

1 Like
5

Thank you for sharing that. I followed your advice, and used 0.99 instead of 1; which stopped the morph failure.

Hopefully 5.7.2 will have a fix for this.

6

I’m getting the same issue in the Cropout Sample Project for 5.7.1. See attachment.

  1. Create project of Cropout Sample Project for 5.7.1.
  2. Enable Skeletal Mesh Morph Target Editing Tools and restart the editor.
  3. Add a new morph target to SKM_Villager.
  4. Activate Morph Target for editing.
  5. Change the shape, apply to asset and save.
  6. Switching between 0.0 and any other value will leave the morph at the last non-zero value.
  7. CPU vs GPU skinning makes no difference.
  8. This does not happen with mesh deformers! That is: Enable Allow Mesh Deformer and assign one of the assets that appears when the Plugin Content filter is enabled**.**

2026-01-05 11-18-05.mkv (2.7 MB)

7

On a side-note, we’ve experienced similar problems with custom animation curves getting stuck on the last non-zero value in the past. Could be related.

8

The dev has a fix for this. Its too late for 5.7.2 but it’ll be in 5.7.3.

”btw the workaround is to disable skin cache either directly or indirectly via the use of a deformer”

3 Likes