[vtkusers] Distance between points

[Matias Montroull]

Hold on, I tried this:

 float[] p0 = new float[] { 10.2F, 20.7F, 10.4F };
            float[] p1 = new float[] { 10.5F, 20.5F, 10.8F };

            IntPtr pP0 = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(float))
* 3);
            IntPtr pP1 = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(float))
* 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.
            double dotprod = vtkMath.Dot(pP0, pP1);
            double norm = vtkMath.Norm(pP0);


and worked!


On Tue, Jan 14, 2014 at 9:33 PM, Matias Montroull <matimontg at gmail.com>wrote:

> 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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