Using "Update Component Transform to Root Bone" option causes geometry collection particles to appear in the wrong location after the collection breaks

Development Asset Creation
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If the “Update Component Transform to Root Bone” is enabled on a geometry collection which moves from its origin before breaking the particles will not appear in the correct location.

In the example provided, observe that the box falls but, upon breaking, the particles appear below the location they broke at.

The chaos debugger shows the particles in the correct locations

Check boxes on in the detail of the box blueprint actor allow you to either disable the option or apply quick workaround - setting the transform of the component to some arbitrary value, which seems to force a re-sync of the correct positions from the simulation (albeit with a single frame where the object can be seen in the wrong location)

2

Steps to Reproduce

  1. Open the repro project
  2. Start simulation

alternatively

  1. Make a simple, fractured, geometry collection
  2. Place this geometry collection into a level where it will fall onto, and collide with, another object
  3. Set low damage threshold values so it will reliably break
  4. Enable the option “Update Component Transform to Root Bone” on the geometry collection component
  5. Start simulation

Versions tested: 5.5, 5.6

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Hello [mention removed]​

Thank you again for reaching out and reporting this issue.

After investigating, I’ve gone ahead and made a JIRA report to be added to the Unreal issue tracker website (https://issues.unrealengine.com).

Please note that Epic ultimately determines whether the issue will be made publicly accessible, and the process can take a few days; therefore, the tracking link may not be immediately accessible.

Once available, you will be able to track the resolution at Unreal Engine Issues and Bug Tracker (UE\-297788)

I’ll close the case, but feel free to reply if you have anything else to add.

All the best,

[mention removed]​

4

Hello [mention removed]​

Thank you for reaching out and bringing this issue to our attention.

Also, thank you for taking the time to create a repro project!

I was able to verify what you described.

It looks like there’s an offset between the render and the physics, as seen in these images:

Viewport:

[Image Removed]Chaos Visual Debugger:

[Image Removed]

I’ll investigate some more and get back to you.

All the best,

[mention removed]​