[vtkusers] Distance between points

[David Gobbi]

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);
>
>