[vtkusers] Distance between points

[Matias Montroull]

I get 6.6225 and "Infinity"...


On Tue, Jan 14, 2014 at 9:21 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> You should try these other math methods to see if they also give
> incorrect results:
>
>   double dotprod = vtkMath.Dot(pP0, pP1);
>   double norm = vtkMath.Norm(pP0);
>
> For your values of p0 and p1, they should return:
> dotprod: 643.77
> norm: 25.3118549300520
>
> On Tue, Jan 14, 2014 at 5:03 PM, Matias Montroull <matimontg at gmail.com>
> wrote:
> > It is weird that it doesn't work in ActiViz... It's the same code, maybe
> it
> > is the overload function you mentioned?
> >
> >
> > On Tue, Jan 14, 2014 at 8:58 PM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> >>
> >> I just tried it in Python, and it works there just fine.  And you can
> >> be sure that it works in C++, because it is one of the most-used
> >> methods in VTK, and hundreds of the VTK tests would fail if it was
> >> giving the wrong answer.
> >>
> >> The distances that I get are:
> >>
> >> p0 = (10.2, 20.7, 10.4)
> >> p1 = (10.5, 20.5, 10.8)
> >> vtkMath.Distance2BetweenPoints(p0, p1)
> >> 0.29000000000000042
> >> math.sqrt(vtk.vtkMath.Distance2BetweenPoints(p0, p1))
> >> 0.53851648071345082
> >>
> >>
> >> On Tue, Jan 14, 2014 at 4:53 PM, Matias Montroull <matimontg at gmail.com>
> >> wrote:
> >> > Thanks, I will take into account your suggestion.
> >> >
> >> > Can you run the code with those point samples and tell me what's the
> >> > distance you get? I'd like to ensure it works in C++ and then figure
> out
> >> > how
> >> > to make it work in ActiViz..
> >> >
> >> > Thanks,
> >> >
> >> >
> >> > On Tue, Jan 14, 2014 at 8:48 PM, David Gobbi <david.gobbi at gmail.com>
> >> > wrote:
> >> >>
> >> >> Hi Matias,
> >> >>
> >> >> I don't use Activiz, but something about your code confuses me:
> >> >> In C++, Distance2BetweenPoints is overloaded for float and double:
> >> >>
> >> >>   float Distance2BetweenPoints(const float x[3], const float y[3])
> >> >>   double Distance2BetweenPoints(const double x[3], const double y[3])
> >> >>
> >> >> So how does Activiz know which one of these methods to call?
> >> >> If it passes a "double" IntPtr to the float-overloaded method, then
> the
> >> >> result is definitely going to be wrong.
> >> >>
> >> >> Also: I suggest that you include "Activiz" or "C#" in the subject
> line
> >> >> of all your emails to the list.  That will help to attract the
> >> >> attention
> >> >> of
> >> >> other Activis users, and they are the ones who are most likely to
> know
> >> >> the answers to questions like this one.
> >> >>
> >> >>   David
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> On Tue, Jan 14, 2014 at 4:18 PM, Matias Montroull <
> matimontg at gmail.com>
> >> >> wrote:
> >> >> > Hi,
> >> >> >
> >> >> > I'm running this code and I get distance "infinity"... If I change
> to
> >> >> > lower
> >> >> > values (1 digit) then it gives a distance..
> >> >> > Why?
> >> >> >
> >> >> >  double[] p0 = new double[] { 10.2, 20.7, 10.4 };
> >> >> >    double[] p1 = new double[] { 10.5, 20.5, 10.8};
> >> >> >
> >> >> >    IntPtr pP0 =
> Marshal.AllocHGlobal(Marshal.SizeOf(typeof(double)) *
> >> >> > 3);
> >> >> >    IntPtr pP1 =
> Marshal.AllocHGlobal(Marshal.SizeOf(typeof(double)) *
> >> >> > 3);
> >> >> >    Marshal.Copy(p0, 0, pP0, 3);
> >> >> >    Marshal.Copy(p1, 0, pP1, 3);
> >> >> >
> >> >> >    // Find the squared distance between the points.
> >> >> >    double squaredDistance = vtkMath.Distance2BetweenPoints(pP0,
> pP1);
> >> >> >
> >> >> >    // Take the square root to get the Euclidean distance between
> the
> >> >> > points.
> >> >> >    double distance = Math.Sqrt(squaredDistance);
> >> >> >
> >> >> >    // Output the results.
> >> >> >    Console.WriteLine("SquaredDistance = " + squaredDistance);
> >> >> >    Console.WriteLine("Distance = " + distance);
> >> >> >    Marshal.FreeHGlobal(pP0);
> >> >> >    Marshal.FreeHGlobal(pP1);
> >> >
> >> >
> >
> >
>
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