[vtkusers] More fine-grained vtkMarchingCubes

[Vladimir Lazunin]

I use vtkMarchingCubes to extract a surface from a voxel data. Naturally,  
I get a surface which looks like "stairs". Which parameter shall I change  
to make each step of that "stairs" smaller (increasing their number, of  
course), or bigger (decreasing their number)?