The landscape in one of my maps had its mobility changed from Static to Movable somehow (still not clear on how this happened since Mobility is hidden in the details panel). Today we were trying to move some of our landscape splines around but the engine kept crashing on us. After doing some digging I eventually tracked it down to line 1430 in LandscapeSplines.cpp. When the engine tries to attach the new MeshComponent to MeshComponentOuterSplines it fails because the mobility isn’t static, but it ignores the failure and continues on and ends up crashing further down in the function.
I’m not sure if this is even a fixable bug since the landscape isn’t ever supposed to change mobility (as far as I know anyway) but figured I’d report it just in case.
I should probably add that once I figured out why this was crashing I was able to fix it by writing a function in C++ to change the mobility of all of an actor’s components and calling it on my landscape in a construction script. That doesn’t really feel like a proper use of the construction scripts but it worked.
So in order for us to log this as a bug report and enter a ticket, we need some steps to reproduce this issue on our end. I cannot think of a way to modify the landscapes mobility unless you were to go into code and change it manually.
We will also need your crash logs and ‘dxdiag’ to add to the bug report for verbosity. Please try and narrow down some repro steps and provide us with the necessary information to move forward with the bug reporting process.
After looking through our svn repo and tracking down which commit caused this crash to start happening, I was able to find some repro steps. It looks like if you add a landscape to sequencer and give it a transform track it changes the mobility to movable (specifically in MovieScene3DTransformTrackInstance.cpp in UpdateRuntimeMobility). My artist said it’s likely he had auto-key turned on and accidentally selected/moved the landscape while he was modifying a sequence.
Repro steps for this:
Create a new project.
Create a landscape in a blank map.
Add a spline with 2 control points.
Create a sequence.
Turn auto-key on in sequencer and move the landscape.
Save everything (not strictly necessary but it will allow you to go straight to the crash on subsequent attempts instead of setting up the sequence track each time).
Go to the landscape editor mode and try to move or add a control point.
Editor crashes.
I’m attaching a sample project, a copy/paste of the call stack I get when it crashes, and my dxdiag. I’d provide the crash log itself but I can’t find it. According to A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums it should be in AppData but I don’t have a ReportQueue folder in AppData/Local/Microsoft/Windows/WER so I couldn’t find it.
Thanks for the clear and precise repro steps. I was able to confirm what you are reporting and have gone ahead and entered a bug report for the issue. You can track the report following the link below on our public issues tracker.
Once the issue has been addressed by our engineers the ticket will be updated and reflected in the public tracker. Let me know if you have further questions or need additional assistance.