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Point position detection

Started by Arch Mar 8, 2003 at 3:30 AM 2 replies 200+ views

Original Post

Mar 8, 2003 at 3:30 AM

Which is the faster metod to determine if a point is inside a polygon after I have verify than the point belong to the polygon''s plane ?? Thanks

JuNC

Mar 8, 2003 at 4:35 AM

''Faster'' is debatable, an easy way is to use the cross product test:

  
bool TestPtInFace(const std::vector<Point3>& pts,const Point3& pt,const Vector3& normal)
{
  int ptCount = pts.size();

  for(int i=0;i<ptCount;i++)
  {
    Vector3 edge = pts[(i+1)%ptCount] - pts[i];

    if(Dot( Cross( edge, pt - pts[i] ),normal ) < 0)
      return false;
  }
  return true;
}

Some say the barycentric method is better, others that some other way is better. At least the above code should work even if it''s not optimal.

tok_junior

Mar 8, 2003 at 6:39 AM

Would i be entirely wrong if i said that you should be able to dot the point with all three vertices of the triangle, and add the results together? If the result is 180 degrees it''s inside...
Something like that atleast ;P

--
MFC is sorta like the swedish police... It''''s full of crap, and nothing can communicate with anything else.

Arch

Mar 8, 2003 at 7:05 AM

Anybody know the HAINES (1991) metod ?

Thanks

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