4.7.2 Project Update, Huge performance drop and bugs

Hi !

Recently, we tried to update our project from the 4.5.1 version who works fine . In the 4.7.2, we find a very huge performance drop ( some scenes cause crashes and windows bluescreen ) . After some research we find the two things who are responsible :

  • 1°) We need to reimport all static meshes and finding the source even if the import folder ( in static mesh settings ) is correct . After that, performance seems to be a lot better .
  • 2°) By deactivating tesselation, we finished to resolve the problem . We are using PN triangles and it causes problem only when using foliage editor, it works fine when just drag and drop static meshes on a floor . Even with no subdivision, it slows down a lot and a bit of subdivision cause crashes . It’s really strange, in 4.5.1 tesselation worked really well .

Finally we find a problem with distance field AO with theses artifacts you can see on the picture ( that’s a problem who appeared in previous version too, but with the new 4.7.2 it’s really strong ) .

Hi Red Gnash,

Typically it’s better to post all issues individually to make them easier to track and look into. I am happy to help look into these issues though.

  1. Do you have a call stack or any crash logs and dmp files from the project when this crash occurred?

  2. I tried testing a simple material with tessellation enabled (basic color with a constant value of 8 for the tessellation multiplier) with foliage tool but didn’t see a significant drop in FPS with ~6500 instances placed. Would you mind sharing the material setup and I can see if maybe a more complex material can provide different results.

  3. DFAO - This was mostly resolved in 4.7.2 with newly created projects. There have not been as many issues reported that this is still an issue, but our Rendering team is aware of the problem.


First of all, thank you for your answer and sorry, we thought that theses 3 issues were realted to the updating problem, so this is why we grouped them in the same post . So, here is what you need :

  1. In fact the computer crashed and restarted with a bluescreen

  2. Here is my material setup

Were there any logs created from the crash?

These would normally be kept in the Project Folder > Saved > Logs (just zip this and attach).

When the crash happened it just blue screened. Did that just happen once or is that continuing to happen? If so, there may be a crash log that Windows generates that can be located in C:\Users[YourComputerName]\AppData\Local\Microsoft\Windows\WER\ReportQueue

This folder location will hold any crash logs that have happened with any program or windows itself. If the crash is continuing to happen it would be better to delete everything in this folder then reproduce the crash.

If the crash is no longer happening this could make it nearly impossible to distinguish what was happening to create the BSOD.

It happened every time we tried to load a scene ( with a lot of instances ) but we fixed it by reimporting assets and deactivating tesselation . Also I’ve no windows or ue crash logs for theses crashes .

Hey Tim, I’m working with Red Gnash, on my computer I didn’t get a BSOD but my video drivers would always crash, you can see the log created here : link text

Those crashes seemed to be fixed by reimporting the assets though.

The major issue we have to deal with now is the performance drop that seems to be fixed by deactivating tesselation. Do you see anything in the material set up that could cause this? Or could it be an other problem due to assets importing?


Apologies for the delay.

I am able to see the slow down when using the material setup like your image. I’ve applied this specifically to a SpeedTree asset (Free Sample of the Broadleaf_Desktop) and applied the material to the First material slot for the bark.

I see the slow down for the instanced meshes placed with the foliage tool, but not with individually placed trees.

For example. I setup two scenes. On average I get ~80 fps in this default scene.

With the instanced meshes placed with the foliage tool I see a significant drop in performance down to ~15 fps.

With individually placed meshes I see ~65-70 fps.

I placed 12 of each. Any more than that and my performance with the instances is no longer real-time and is now a slide show. I’m continuing to look into this and want to test this a little more before submitting a ticket.

Thanks for your patience while I look into this.

Apologies for the late reply.

I was able to test this in 4.7.5 with the FPS degradation, but when bring the same project into our internal build of 4.8 I was not able to see the same loss in FPS.

In your material, I removed everything but the world displacement pin. Everything else was irrelevant to this issue as the slow down was caused specifically in this part of the material. When this is disconnected and PN or FN tessellation is enabled there is no slow down.

For the moment this looks like it’s been improved with 4.8. At the moment there is no official release date for 4.8. Once it releases can you test this and let me know if you’re still having the issue.

Thank you!


Okay, thank you for your reply