Jumping to specific frame in morph target animations broken in UE5.7

Development Rendering
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This issue was noted while migrating our project from UE5.5 to UE5.7. When jumping in time inside the level sequence that animates a skeletal mesh with morph targets, the skeletal mesh is not updated when setting the play-head at the very first frame of the morph target animation or somewhere before.

This issue seems to be visible only when setting cvar “r.SkinCache.CompileShaders=True”. In our project this is required due to “r.RayTracing=True”. The issue cannot be reproduced in UE5.5.

Tested with UE 5.7.2 and confirmed the issue is still present.

2

Steps to Reproduce

  • Open level “Reproducer_Sample”
  • Open level sequence “LevelSequence”

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  • Play animation and watch the actor “FbxScene_Assembly”

--> Starting from frame 500 skeletal mesh “Rollo” and static mesh “Animated_Cube” are moving into -X

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  • When finished, set the play-head to frame 500 or to any frame before

--> “Animated_Cube” is moving to the correct position whereas skeletal mesh is not updated at all

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3

Hey there,

We’ve fixed this issue in a recent submission, and it will be released in a hotfix (5.7.3). If you are running a code project, you can integrate this change:

https://github.com/EpicGames/UnrealEngine/commit/71004a086e7a6a1bbf2dfa2243d1ff735445bc62

Dustin

4

Hi Dustin, thank you so much for that quick response and fix!