Fracturing a mesh in editor causes broken result

Backov · February 24, 2015, 4:50am

Engine version 4.6.1

I’m trying to use the DM support. I’ve imported a static mesh and created a destructible:

Then I’ve done a simple fracture:

This is obviously very broken. I haven’t had this issue with any other meshes.

I’ve [attached the FBX][3] that demonstrates this issue.

NOTE: Importing this mesh into Physx lab 1.3 and fracturing it there works as expected.

Tim_Hobson · February 24, 2015, 6:54pm

Hi Backov,

Meshes that are going to be setup for destruction work best when they have been setup in a specific way for their edges. While I can see in your mesh that the everything has quads that can be triangulated, it doesn’t react well with DMs. By adjusting some verts and stitching them to other verts there is no loss of geometry definition, only removal of extra faces.

You can see the difference in wireframes with this picture: http://screencast.com/t/JnQvsg6jaC

Here is the results when fracturing the mesh that has the adjusted edge placement: http://screencast.com/t/42A4hv13wtx

Updated FBX: Dropbox - Error

Backov · February 25, 2015, 1:45am

Your answer would make sense if the fbx didn’t fracture perfectly in Physx Lab. If you then export to an APB and import into UE4, it works perfectly there as well.

This is a bug in your fracture generation.

Tim_Hobson · February 25, 2015, 6:51pm

You’re right. I didn’t pay attention to the edit for it working differently than PXL.

I’ve entered UE-10835 for this issue to be reviewed by our engineers.

Thank you!

Tim

Tim_Hobson · March 19, 2015, 9:59pm

I wanted to update on this issue. The engineers have decided that this issue will not be fixed. While in-editor fracture tools will be improved it cannot be guaranteed that they will always match that of PhysXLabs. Using the methods previously mentioned as a workaround will be the route to go with correcting the issue with UE4.