CGAL users discussion list

[Alex Tsui <>]

On Wed, Feb 15, 2012 at 6:41 PM, ckehoe <> wrote:

Hello,

I've got a question about surface reconstruction with CGAL. I downloaded and
ran the reconstruction demo, but I'm not sure how to modify it for my
situation. There are two differences I need to deal with:

1. I don't have normals for my points. My surface is pretty smooth, so
normal estimation should work, but I couldn't find the documentation that
actually described how to do this. Can anyone point me in the right
direction?

The point set processing package has a way to estimate normals, see also the example here:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Point_set_processing_3/Chapter_main.html#Section_57.7
 

2. I have colors that need to be assigned to each point, so I need to track
the points in some way as they go through the algorithm. I don't entirely
understand the data structures CGAL uses, since I don't have a strong
computer graphics background. How can I deal with this situation?

The CGAL polyhedron data structure has a list of vertices, and I think by default, the vertices only save point information. You can extend the vertex to save color data, eg.
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Point_set_processing_3/Chapter_main.html#Section_57.7

I haven't used point set reconstruction much, but I noticed that the input points are, in general, different from the points in your output polyhedron. I don't know if you will be able to start with colored points in a point cloud and have it carry through the surface reconstruction -- I think all CGAL does is use the point cloud to compute a function for the surface. Can you give more detail about what you need to do with colors?
 

Thanks in advance for any help you can give.

- Charlie


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--Alex
 

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