Trying to build a globe in UDK, but when I do (create a sphere), my player falls straight through it. How do I make a sphere that I can walk on? Every other shape (cube, cone...etc) work just fine.

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Edit: Specifically, I want to build a CSG/Brush sphere, not a mesh sphere. It appears to work just fine if I set the "sphere exptrapolation" to 1 or 2, but if I bump it up to 3 or higher, I fall right through. I literally created 2 spheres next to each other, one set at "2" and one at "3" - I can walk from the top of the "2" sphere and jump onto the "3" sphere, but I fall right through it.