Unreal Engine 4.20 Preview

I’m finding it very weird that no one seems to be bringing up anything about the HISM component. I’ve been having problems with it on 4.20 since I started testing it on preview 2. But only this week I’ve had the time to set up reproduction steps.

I’m really thrilled about this release. Been loving to work with Layered Materials, but in 4.19 you can’t reorder them and sometimes it takes more than 5 minutes to re-setup materials above a new inserted one that should go in the middle of the others. It’ll be very sad to have to stick to 4.19 because of HISM bugs. And I’m using them a lot. It’s a huge environment with several repeated pieces. Not to mention the new DoF that’s awesome for showing the work to your customer.

I’m also using HISMCs a lot, and actually, there’s a very horrible bug with HISMCs in both 4.19 and 4.20:

This is how it looks like when you call AddInstance in 4.18:

And this is 4.19 and 4.20:

So adding instances on runtime is completely broken visually if you have any wind in your level, the wind seems to get reset for all existing instances when new ones are added in 4.19 and 4.20.

This breaks my game unfortunately, so I very much hope it get’s fixed soon.

I’ve posted about it on the AH too: Very bad regression with AddInstance for HISMC in 4.19, wind gets reset for all existing instances - UE4 AnswerHub

How does the wind system work in Unreal? Is it animated by a time variable?

Those trees are using the Speedtree wind node, which is more complex I guess.

Per instance random gets generated once again ? (speedtree shader uses time & perInstanceRandom)

Did you file a bur report already. Would love to upvote the issue :smiley: as I did with your AH post :smiley:

I found the cause of the problem by comparing the two DefaultEngine.ini from 4.19 and 4.20 when creating a AR Template project.

It’s this setting in 4.19:


which is changed in 4.20 to:


When I change this in my project it works in 4.20 :slight_smile: Pretty annoying though and I guess everyone upgrading their AR project will run into this.

This is because mac os is not whitelisted in plugins (mixed reality and opencv). I’ve added Mac to whitelist and everything works fine.

Looking at the HISMC code, it should not generate the per instance random again. Regenerating the random stream is disabled when a new instance is added, so if there’s a bug with that then I assume it’s not in the HISMC code but somewhere deeper.

Yes, I submitted it to Epic, including the repro project. Have not heard anything back from them though.

Actually, that HISMC bug is even worse, it also happens when you update **any **existinginstance, not just when you add new ones. So if you have trees that are growing or anything similar, all existing instances will get their wind reset:




Actually, we found a “fix”: If there’s any static mesh existing and visible with the same mesh like the HISMC, the issue does not appear.

Sweet! The project generator for CLion appears to be fixed since Preview 4. The CMakeList is there and from what I’ve observed, I needed to launch CLion twice so that it can load the project structure.
A few things aren’t picked up from the code completion, like GetWorld()->GetDeltaSeconds() as an example. Nothing to be worried about.

Time to play more with it and see how the refactoring will work :smiley:

And that’s why, toghether with the bug report, I post it on answerhub bug session. So that others can help/be helped with discovered workarounds.

On Preview 5 materials are compiling very slowly. Even using XGE, only one ShaderCompileWorker instance is being launched at a time in IncrediBuild (Windows). I didn’t notice this slowdown in Preview 4.

Edit: I’ve also upgraded IncrediBuild, right after installing Preview 5, so it may or not be the cause.

why is this labeled won’t fix?

Because Fortnite doesn’t use Forward Renderer ? :rolleyes:

It doesn’t? I thought it did use the forward renderer at least on the Switch.

I think it’s only used in RoboRecall.

@Amanda.Bott When I click on the “Unresolved issues in 4.20 Preview targeted to be fixed by the 4.20 Release” link, it says"I tried but couldn’t find anything…". Something seems wrong there?

Bingo! It’s kinda sad to see VR rendering isn’t being developed further :frowning:

Well, given that, I’d also very much like to know why the issue isn’t being fixed. @Amanda.Bott or @DanielW could anyone provide us with some info as to why Unreal Engine Issues and Bug Tracker (UE-61513) is marked as “Won’t Fix”?


The reason was edited into the issue page: