[vtkusers] Better way to draw vertex normals?

[Feng Ding]

Dear list,

I'm trying to draw a normal line for each vertex on a 3D surface mesh,
which contains n vertices. My current method uses vtkLineSource to
represent the normal line. Then, for each normal line, I create its
corresponding polyDataMapper and Actor in order to draw it in the
render window. Here's my problem: when n is a large number, rendering
n Actors is very slow. Is there any better way to draw vertex normals?
Possible to draw multiple vtkLineSource objects using only one
polyDataMapper and one Actor?  Thanks!

Best regards,
DING Feng