[vtkusers] display arrows on a surface mesh

[David Doria]

On Tue, Dec 8, 2009 at 8:23 AM, Zhangyuanchao <woshizhangyc at yahoo.cn> wrote:

> Hi, there,
>
> I would like to display arrows on a closed surface mesh. Given that the the
> arrows may point inside and outside the surface, I can see the arrows
> pointing outside the surface using vtkGlyph3D and vtkArrowSource. However,
> the arrows pointing inside is not visable. How can I pull out the arrows
> pointing inside?
>
> Is there any function by which I can chang the role between the start
> point  and end point of an arrow?
> or How can I manage to solve the problem? Is there any other way?
>
> Thanks a lot!
>
> yuanchao
>
>
If you have an analytical definition of "inside" you can simply iterate
through the normals and negate any that are not facing "inside". Typically,
this is a very hard thing to define.

I have just written an article for the VTK Journal (not yet released!) in
which I have implemented a method to orient normals.
I tried to pull out the relevant parts and post an early preview for you:
http://www.rpi.edu/~doriad/VTK_List/vtkPointSetProcessing/

The directory structure of the CMakeLists.txt but if you want it bad enough
you should have all the pieces there!

I really think this is something that should be added to VTK - it is
something that will help us compete a bit more with CGAL :) We'll discuss
more once the VJ is ready and the paper is released :)

Thanks,

David
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