Mutable. Issue with ClipWithUVMask crashing or producing invalid results.

Development Character & Animation
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1

We are attempting to use Mutable in 5.6.1 and have encountered an issue which we are not sure how to resolve.

The issue occurs when using the ClipWithUVMask node.

In short we have a customizable object with an enum and based on this enum value we either use or don’t use a clip mask to cut out a part of a mesh. In 5.5 this worked without issue but once we attempted to upgrade to 5.6 this completely stopped working.

I have provided a zipped project with everything needed to repro this.

I have also provided images that show the various setups from the repro steps.

For issue 1 see attachment “crash.png”

For issue 2 see attachment “workaround.png”

For issue 3 see attachment “notworking.png”

There is a forum thread created by someone else with this issue here: Mutable 'Clip With UV Mask' node crashes editor in 5.6.1

2

Steps to Reproduce
Preparation:

1) Download provided zipped project and launch with 5.6.1 (works with both launcher version and Release-5.6.1 stream)

2) Open CO_Example asset

3) Notice that there are 3 ClipWithUVMask nodes. I will call them Clip1, Clip2, Clip3 from top to bottom.

Issue 1 (Crash)

Connect Clip3 to the modifiers array. Disconnect Clip1 and Clip2. Compile the asset. The editor runs into a check() and crashes. If crash is skipped (via debugging in continuing) the produced results are invalid.

Issue 2 (Workaround for issue 1 but an issue in and of itself)

Connect Clip1 and Clip3 to the modifiers array. Disconnect Clip2. Compile the asset. This produces the desired result (the clip mask is properly used) but the fact that we need an empty texture parameter to make this work is just wrong.

Issue 3 (Real issue that we are running into in our project)

Connect Clip2. Disconnect Clip 1 and Clip3. Compile the asset. Iterate through the enum values in the Preview Instance and notice that on enum value 3 (where the texture for the clipmask is used) the produced result is not valid (As seen in the result of Issue 2). Notice that the workaround noted in Issue 2 does not change the produced result.

Conclusion: Something is wrong with texture loading.

3

Hey there, apologies for the delay, I was trying to figure out what change exactly caused the issue and wasn’t able to pinpoint it.

I’ve logged a bug that you can follow here: Unreal Engine Issues and Bug Tracker (UE\-331604), it could take 24 hoours before it will show up.

4

I see that the target fix has been set to 5.8. Is there any hope to get some help with this issue beforehand? Something we could apply to the engine ourselves locally and test?

5

Hey there, yes the target fix has been slated for 5.8 as the team is wrapping issues and bug fixes for 5.7. As a bug fix happens, I can let you know and then link the CL that you can apply to the engine. There may be more than one.

Dustin