How to compute volume of 3D object using contours?

Hello;

what if i am having a set of points that represent a counter of 3D object and i want to measure its volume?!

 load('Contours.mat');
figure,hold on,
for i=1:8, 
    S=DataSet{i};         
    plot3(S(:,1),S(:,2),S(:,3));
end

Thanks a lot!