Fracture Mesh on destructible deletes my material

When I hit “Fracture Mesh” on a destructible, the material of the inner chunks gets deleted. Even after adding a material to the index for the inner chunks, it doesn’t show in-game when fractured.

Hi Ianoreo,

I’ve just tested this with 4.7.6 and I’m not able to see this same behavior.

  • Can you provide your exact steps to reproduce this?
  • Was this Destructible created using UE4 or PhysX Labs?
  • Is the material slot disappearing in the Destruction editor or just the details panel in the main viewport?

Can you post a screenshot of your issue? This can be more helpful in determining what you’re seeing and help me diagnose what’s going on more quickly.

Thank you!


Hi Tim! Thanks for the response.

So I updated from 4.7.5 to 4.7.6 just to confirm it wasn’t a little bug, but still seeing this. So I had a Destructible that was set up in the game that had two materials, but I realized I was using way too many cells! Became laggy when too many were fractured. So I decided to go back into the Destruction editor and reduce the cell site count. I re-fractured, but when I did so, the 2nd material (the inner chunk material, that is) was removed. I figured this was fine, that I could simply add a new material to the index “1” and plug in my inner material. However, when this has been placed in the world (it’s a BP), the inner material is not visible, nor is the inner material visible within the destruction editor. I have confirmed the material is set in the blueprint itself as well. I’ve also tried to a material override within the blueprint but this doesn’t seem to fix it either.

I uploaded a little screen capture of the process to youtube:


I can reproduce this when I have a mesh that has open faces or is not a fully enclosed mesh. This is not a bug, but just a limitation of the fracture method.

You can read some of the limitations in this AnswerHub post I’ve made previously: Solid objects losing faces during destructible mesh - Asset Creation - Epic Developer Community Forums

If a mesh is not fully closed as a single piece of geometry you will see holes in the mesh. This is because the Voronoi fracture method needs the mesh to be a solid 3 dimensional object that has no openings. If there are openings the inside faces will not render which happens when you fracture the mesh. If you add a material, it’s not assigned to any inside faces, because they do not exist. This is why when you hit the fracture button again it will clear the extraneous material that is not needed.

If you’re unsure you can post the static mesh this was created from and I can take a look for you.

Let me know.


Hey Tim!

I was wondering if it was just a mesh issue. I’ll go back into Maya and find the holes. Thanks for your help on this one!