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I've know of this but I've never known exactly where the option is. I know that you're limited to one collision per item and that Autofit is technically an example but I've never known anything past that.
Just off the top of my head, if the item already has a smoothing modifier put on it, then you'll find it under paramaters --> general--> mesh smoothing.
If it doesn't have a modifier already on it, then select it in the scene tab and then (i think go to edit-->figure-->smoothing modifier. That may not be right. (or edit-->object-->smoothing modifier if you're working with an object, not a figure.) That should be enough to get you in the right area of the menu, if it's not quite right. (I'm away from my own computer right now.)