Fracture Mesh freezes UE4

Hi everybody, I’m having trouble fracturing one of my meshes. When I hit the Fracture button UE4 just freezes and never starts again. It’s around 8000 polys. I tried with another mesh and that one worked fine but this one is giving me problems.
I’ve attached it if anybody wants to take a look for themselves.


Looking at the mesh, that is a VERY high-poly mesh at around 15k triangles in UE4! If you only intend to use the in-editor tools, I would start by making a much lower poly version of the mesh by uisng the Mesh Reduction tools in the static mesh editor. Then, I would create the destructible mesh from that to fracture.

The problem you’re going to run into with a high-poly mesh is that depending on the specs of your machine (even a high-end one) you can run into the editor freezing while it is processing the mesh and applying the fracture. If you wait it out (could be a very long time!) you’ll get the fractured mesh. Also depends on the number of chunks you’re trying to fracture the destructible mesh into as well.

If the intention is for this to be a planet that explodes or can be destroyed in some manner, I wouldn’t actually use destructible mesh for this. I would manually break the model apart in my modeling application into large and smaller chunks and then when the mesh is hit and receives some specified amount of damage I swap out the original mesh with the chunks that can break apart and use some cool VFX particles. With a Destructible Mesh, you’ll run into issues where the pieces should never get too far away from one another, they can be expensive to use because they are only handled on the CPU and not the GPU, and if you’re intending to use a high-chunk fracture count you can only ever have 2000 chunks visible on screen at once (this number can be increased via .ini changes, but I don’t recommend it).

Thank you for your answer. I found that even after reducing the mesh to 5000 tris it still froze the editor when attempting to fracture the mesh. Which is odd, because the other mesh I tested with was about 18k tris and that worked perfectly.

Either way, 15k tris is way overkill considering how simple my object is. I’ll probably just use a normal or displacement map on a simple sphere and see how that works out. Or take your suggestion and swap the mesh out on impact.


it can just depend on the complexity of the mesh, meaning not simply the poly count but how the geometry is laid out for the mesh that is being fractured.

I experimented with those destructibles too… Cube may take 1s to fracture to 200 pieces… when i tried sphere, i had to wait about 10 minutes.