UE 5.2's new Animation Compression changes introducing DDC invalidation each Editor startup?

Development Character & Animation
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Hi Dev Community,

We recently switched over to the 5.2 preview.
We leverage a local user Derived Data Cache (DDC) per machine and our drop includes the Animation Compression changes from CL 23510521. These changes can be found here:
https://github.com/EpicGames/UnrealEngine/commit/31f1b097fd1507b848d62537d2d7c86986128bc4

We see two issues that may be closely related:

  1. AnimSequence::PopulateModel descends to UAnimationSequencerDataModel::GenerateGuid.

This GUID calculation acts non-deterministic from run to run (same machine + build + local DDC + asset), preventing the DDC from picking it up.
Here is the NotificationCollection that triggers the Modify:
image

  1. BeginCacheDerivedDataForCurrentPlatform descends to UAnimSequence::CreateDerivedDataKeyHash from the same OnModelModified call as #1.

The GUID calculation acts non-deterministic compared to #1.
Changing GetDataModel()->GenerateGuid() within UAnimSequence::CreateDerivedDataKeyHash to instead be
FGuid guid1(0, 0, 0, 1);

Results in 95%+ positive DDC fetches on subsequent runs, but won’t be sufficient if the asset itself changes.

We see upcoming changing for 5.3 from about 2 weeks ago.
CL 4421496

https://github.com/EpicGames/UnrealEngine/commit/502797ca50c381928f5dec3edac62208811a8417

Perhaps we need a patch that restores functionality for the DDC?

Thanks so much,

  • Jeff Dixon
3 Likes
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What dcc?

I have never relied on the engine to pick up on anything, nor has any team I have ever worked with.

Essentially, click re-import and re-select the FBX for the individual animation once per session, or edit at times, (assuming this is the invalidated link you are talking about, but maybe you are using some live plugin or similar missing from the problem description above?)

3

This is related to a Derived Data Cache issue. I updated the note to reflect this.

Thanks,

  • Jeff Dixon
1 Like
4

I found a similar problem, and then I disabled the Animation Data Plugin, everything returned to the previous, I hope it can help you

2 Likes
5

Thank you. I was getting tired of the long start up times of the editor.

6

I don’t know what that plugin was actually doing but I do know that my project’s memory usage also dropped several GB by disabling it, in addition to fixing the startup load times. However I also seem to get crashes on any animations that were added to the game since I updated to 5.2 with the error

Invalid Animation Sequence base state, no data model found past upgrade object version.

Even attempting to open these AnimSequences in the editor or force a reimport will cause the engine to crash.

So unfortunately I had to turn it back on.

2 Likes