center of 3D convexhull

Hi,

I have a hollow 3-D surface (like a hat!) How can I find its centre (it should be somewhere in the hollow space, in the hat!) There is such solution for 2-D image. I mean we can use bwconvhull and then find the centre of 2-D binary image. what about for 3-D??

Thank you for your answer in advance :))