Changing Inst Mesh Comp Transform results in inaccurate instance collisions

Hi, I have been experiencing a very annoying bug and I finally decided to track down the root cause. Below, you will find a youtube video.

Scaling an “Instanced Static Mesh Component” results in inaccurate collisions for “Static Mesh Instances”.

Steps to recreate:

  1. Create a new blueprint actor

  2. Add an “instanced static mesh component” and then set the static mesh to something that is not a perfect cube. I am using a cube mesh that is 1024 wide, 1024 long and 256 tall. This is important for properly illustrating the bug.

  3. Here is a blueprint setup:

Expected Result: The collision on the second static mesh instance should be rotated and scaled to accurately fit the visual result of the static mesh.

Actual Result: The collision does not get scaled, and is merely rotated, resulting in inaccurate collision and the player can clip through the left and right side of the cube mesh.

Why I believe this happens: Setting the transform of an instanced static mesh component causes all subsequent instances to potentially have inaccurate collision. Some instances will have correct collision while some will have completely incorrect collision and this depends on each instance’s transform values.

I have included a youtube video for demonstration to help illustrate the bug.

Hi CaptianMigraine,

Thank you for the report. I was able to reproduce this behavior so I’ve created JIRA UE-42297 and our developers will be investigating further. Follow that link to monitor the status of the bug report.

Cheers,

TJ

Thank you!