How do I assign materials to internal surfaces?

Development World Creation
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Geometry Collections User Guide | Unreal Engine 5.4 Documentation | Epic Developer Community (epicgames.com)
“Change the Materials of Geometry Collections”

I created my geometry collection like the one shown after “Deselect the Show Bone Colors checkbox” using 2 SM_ChaosPrim_Box and 1 SM_ChaosPrim_Bully actors whose assets were migrated from Content Examples.

  • The Materials section is not like what is said in “each original Material ID has been duplicated from the source Asset”, there are 2 materials that are not duplicated. Then how can I assign the internal materials.

Thanks.

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I don’t know if this is still an open question, but posting an answer for whoever else is looking.

To set the internal material, open the Geometry Collection and add a new material to the Materials array. Save the Geometry Collection.

Then when you are in the Chaos Fracture settings window, scroll down to Materials and set the Internal Material to be the material you added earlier.

Make sure to set it in the fracture window. It has some defaults and/or legacy behavior to try to figure out what is inside or outside if you don’t specify, but this can get strange.

I’m still working through this as well, so there could easily be other steps/ways to do it.
Hope that helps.