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About : This tutorial focuses on Fracture Meshes. Fracture meshes are meshes that have been cut up into chunks by the engine, allowing them to break apart upon being shot/triggered.
Target Audience : Intermediate
Platform : Unreal Engine 3
Last Update : October 2009

Configuring The Mesh

The first thing that must be done is prepare a regular staticmesh for use as a fractured mesh. To do this open any staticmesh in any (uncooked) package. In my example I opened up a door. Next up, hit the Fracture button in the top toolbar and notice how a big new window opens up.

Start by setting the slider to the desired number of chunks and hit the generate button. As you will see the staticmesh is now divided into chunks.

Beware though, these changes are not actually applied yet until you hit the “Slice” button at the bottom. Do so.

Notice how it will ask you where and how to save this newly created fracture mesh.

Next up, open up the mesh window of this new fractured variant by double clicking it in the generic browser, if it hasn’t opened by itself already. Notice how there are suddenly a whole lot more properties in the right properties panel.

Lets go over a few of these new properties.

  • bCompositeChunksExplode – If you enable this, the entire mesh will explode into pieces when hit, rather than only break where it was shot.
  • FragmentMaxHealth – For testing purposes I put this to 1. Makes it easier to destroy the mesh.
  • FragmentDestroyEffect – This allows you to add a particle system, which will be played when the mesh breaks down. I added an explosion particle in my setup.
  • LodInfo – Be sure to check out the otherwise standard material setup. The editor adds one new material slot to the mesh, so assign a material to it. This material will be shown on the side of the chunks.
  • Close the window and while you keep the fracture mesh selected in the generic browser rightclick somewhere in your level and Add Actor – Add FracturedStaticMesh and the mesh will appear in the level as if it were a regular staticmesh

    You are pretty much done! Play the level and shoot the mesh!

    Additional Options

    Have a look in the properties (F4) of the fractured mesh you placed in your level. A few additional options there.

    Also interesting may be the fact that you can configure each chunk on an individual basis. Open up the fractured mesh in the generic browser again and hit the fracture button again.

    Now try simply clicking on one of the chunks in the viewport. A few options will light up if you successfully selected a chunk.

  • Destroyable – If it can be destroyed or not. Some chunks you may want stay whatever happens, for example the bottom half of a statue.
  • Support Chunk – The rest of the chunks is dependent on this chunk.
  • Spawn No Physics – The chunk will have no physics.
  • Notice the button “Add Core” near the bottom of the window. This allows you to merge in another staticmesh that will act as the “core” of the fractured mesh. The core cannot be destroyed and will stay around forever. That may be useful collision for example. It will make sure there will always be a wall, even if the wall is shot to pieces, and thereby it will not impact gameplay. A concrete pillar for example, may have a bunch of steel bar meshes as a core, to mimic reinforced concrete.

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