[vtkusers] class for image data in polar/spherical coordinate system?

[Wu Ruoyun]

Dear All,

As you know that most of, if not all, ultrasound machines produce data in polar (2D scanner) or spherical (3D scanner) coordinate system. VTK could represent these data using vtkStructuredGrid, as long as each point has its x,y,z coordinates computed and stored. For a set of 3D image data, however, there could be over 8 million points, each means 8M x 3 x 2 bytes memory requirement. It seems that it is quite wasteful to do so.

I am wondering if anyone has a class similar to vtkRectilinearGrid, but representing data in polar or spherical coordinate system. The topology and geometry are all regular, although the geometry may not be rectangular in some or all axis. With that class, we only need to specify the dimension (i,j,k), plus the three angular/linear intervals, in order to setup the data structure. 

Advice on whether it is easy to make one quickly by following the codes of vtkRectilinearGrid would also be appreciated.

Best Wishes!
Ruoyun