[vtkusers] (constrained) delaunay2D issue

[Malcolm Drummond]

Hi Sebastien

1. Yes, you must link with GLU lib

2. Use it freely

3. The GLU tesselator picks up which are external and which are internal contours. It assigns winding numbers for points inside contours - from the OpenGL programmers guide ... 'The winding number of a point is the signed number of revolutions we make around that point while travelling once around the contour (where a counterclockwise revolution is +ve and a clockwise revolution is -ve). When there are several contours, the individual winding numbers are summed.' I keep contours in the same direction and use the winding rule to classify the regions. It's a lot to get into an email - you should get your hands on the OpenGL programmers guide (the Red Book) for a good explanation. My head's been elsewhere for a few weeks but I'm about to start a project where I use the filter a lot so I'll try and write some decent documentation

I'm also working with VC++ 6 so you shouldn't have any problems
I'm sending you the source and some scripts directly

Malcolm 

----- Original Message ----- 
  From: Sebastien MARAUX 
  To: Malcolm Drummond 
  Sent: Friday, March 14, 2003 12:36 PM
  Subject: Re: [vtkusers] (constrained) delaunay2D issue


  Yes, I would appreciate it

  Thank you

  1. I guess I need to link with GL libs after incorporating your 
  sources ?

  2. Can I use it freely (I mean in my company for  commercial 
  application) because I am looking for open and free solutions to tesselate polygons with holes?

  3. are holes defined by negative orientation polygons ?

  Thanks for your help

  Sebastien MARAUX
    ----- Original Message ----- 
    From: Malcolm Drummond 
    To: vtkusers 
    Sent: Friday, March 14, 2003 9:56 AM
    Subject: Re: [vtkusers] (constrained) delaunay2D issue


    Hi Sebastien

    I've been using the GLU tesselator on mining layouts - see attached picture. I have a filter vtkGLUTesselator filter that extends the tesselator filter that is provided with hybrid. Holes, concavity etc are not a problem. I can mail you source code and some demo scripts if you like.

    Malcolm Drummond
    GeoVision cc

    ----- Original Message ----- 
      From: Sebastien MARAUX 
      To: vtkusers at public.kitware.com 
      Sent: Thursday, March 13, 2003 4:23 PM
      Subject: [vtkusers] (constrained) delaunay2D issue


      Hello

      I am using Delaunay2D for triangulating polygons 
      (representing dB levels around airports).

      I prefer this way to tesselate method as it can deal with 
      holes.

      For a special dB level, I can have several polygons defining islands and holes (depending on polygon orientation).

      So I set the polydata as input and as source, so that holes are taken off the object.

      1. there is an issue using this method with most of my 
      polygons : I can obtain "wrong" triangles being holes instead 
      of filled (see enclosed) How can I fix it ?

      2. Is there other ways of dealing with holes, based on 
      tesselate, which would be faster than  this delaunay 
      method?

      Thank you in advance

      Sebastien MARAUX
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