Error saving level

Development World Creation
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1

Problem: Unable to save level (map) to drive D: and loading it from there if InstancedStaticMeshComponent is used in an StaticMeshActor.

Reproduced with both 4.10.4 and 4.11.0 preview 6. In order to reproduce you need a machine with both C: and D: drives and follow the instructions below. For me UE is installed on drive C: (Windows’ drive) and I wanted to keep my project on drive D:. This is when things started to go wrong…

How to reproduce the problem on saving the project:

  1. Create Blank project with starter content (I’m not sure content is necessary, but I did it that way) in a directory on drive D:
  2. Put a cube on the level
  3. Turn it into a StaticMeshActor Blueprint, name it CubeBlueprint
  4. Inside CubeBlueprint’s editor add a new Blueprint component with base class InstancedStaticMeshComponent
  5. Try to save the level. It will save with an error like: “Can’t save Graph is linked to private object(s) in an external package. PhysicsSerializer”

How to reproduce the problem on loading the project:

  1. Either do the above 5 steps again with a project created on C: or remove the cube from the level, save it, close UE, move the project directory to C: and open it from there.
  2. Put a CubeBlueprint instance on the level
  3. Save the project
  4. Close UE
  5. Move the project directory to somewhere on D:
  6. Strart UE, browse the project from D: and try to open, you will end up with an error like these: [4.8 P3] PhysicsSerializer Errors on Project Startup - World Creation - Unreal Engine Forums

I suspect there is some wrong handling of pathnames pointing to a drive different from where UE is installed to.

I can send you my project and even take screenshots or make a desktop video of this issue if you wish.

2

After working more on the project I cannot even save it, despite the project is on C: (same as UE). Error message:

Can't save ../../../../../../UE/Projects/Assembly3/Saved/Autosaves/Game/StarterContent/Maps/Minimal_Default_Auto1.umap: Graph is linked to private object(s) in an external package.
External Object(s):
PhysicsSerializer
PhysicsSerializer
PhysicsSerializer
PhysicsSerializer
PhysicsSerializer
...
  
Try to find the chain of references to that object (may take some time)?

This problem is making 4.10.4 unusable, currently.

3

Hi fviktor,

We were not able to reproduce the issue in UE4.11 preview 6 following both sets of repro steps you’ve provided. Please go ahead and post a link to a desktop video showing how to repro the problem.

Thanks,

.

4

Reproduced the problem both on drive C: and D:. Actually it does not seem to depend on the drive at all, I was just confused by having this problem at the same time as migrating my projects to D:.

New information is that the actor (cube) must have Physics enabled. Otherwise the bug does not happen.

Please find the desktop videos and compressed projects at
https://www.dropbox.com/sh/3k8s6czjjb6af9i/AAAGxXY46LZ5LWszXblDd3yga?dl=0

Download the video files for better quality playback.

I was using UE 4.11.0 preview 6. What I did:

  1. Created simple project named TestD on D:, see video
  2. After adding the actor component I could not save the level anymore due to the error, I saved the rest and closed the editor. Compressed the project as TestD.zip
  3. Did steps 1. and 2. on C:, project is TestC, compressed as TestC.zip
  4. Tried to reopen both projects. It worked, but I had to re-add the Cube_Blueprint actor to the level. Then I managed to save the level.

What I could not reproduce is the loading issues with similar error message I experienced yesterday. (I saw that only in 4.10.4 so far.)

Autosave can also trigger (but does not cause) this problem ending up in an unexpectedly appearing error dialog.

5

One more observation:

The problem seems to happen only if I save the project by pressing Ctrl-S (that’s kind of reflex after each step) or on autosave. If I click the save button from the toolbar on the level editor tab, then it works with no error.

What is the difference between the two methods?

6

Hi fviktor,

Thanks for providing detailed repro steps and following up with the corresponding video files. Using both of these resources I was able to reproduce the issue on just one drive (The D Drive) and have entered the following bug report: JIRA [UE-28061]. When this issue has been resolved, will notify you with an update to this post.

Thanks again for bringing this bug to our attention,

.