[vtkusers] Intersect a ray with a model

[David Doria]

The only thing I could find online is this:

vtkCellLocator::IntersectWithLine

But I have some questions:

1) It says it intersects with a vtkPolyData surface. I have a vtp file
of triangles that I wrote using ->SetPolys(...).  Is that a
"vtkPolyData surface"?
2) What is this vtkCellLocator business? ie. how do I actually call
this function IntersectWithLine?

-- 
Thanks,

David