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Valued Contributor
HelloWorlddd
Posts: 87
Registered: ‎05-03-2013
Message 1 of 5 (193 Views)
Accepted Solution

How to determine a point on one line

193 Views, 4 Replies
03-29-2014 09:47 AM

For example:
pt(0,0,0) is on the line((1,-1,0),(-1,1,0)
then I will get true


pt(1,2,3) is not on the line((1,-1,0),(-1,1,0)
then I will get false

 

Is there exist some method that I can use?

An example will be better. Very Thanks

*Expert Elite*
_gile
Posts: 2,082
Registered: ‎04-29-2006
Message 2 of 5 (180 Views)

Re : How to determine a point on one line

03-29-2014 11:10 AM in reply to: HelloWorlddd

Hi,

 

You can try this overloaded Isinside method;.

 

        private bool IsInside(Line line, Point3d point)
        {
            return IsInside(line.StartPoint, line.EndPoint, point);
        }

        private bool IsInside(LineSegment3d line, Point3d point)
        {
            return IsInside(line.StartPoint, line.EndPoint, point);
        }

        private bool IsInside(Point3d start, Point3d end, Point3d point)
        {
            Vector3d v1 = start.GetVectorTo(point);
            if (v1.IsEqualTo(new Vector3d()))
                return true;
            Vector3d v2 = start.GetVectorTo(end);
            return 
                v1.IsCodirectionalTo(v2) && 
                0.0 <= v1.Length && 
                v1.Length <= v2.Length;
        }

 

 

Gilles Chanteau
Valued Contributor
cdinten
Posts: 61
Registered: ‎11-19-2010
Message 3 of 5 (132 Views)

Re: How to determine a point on one line

03-30-2014 08:09 PM in reply to: HelloWorlddd

one way is using Curve3d.IsOn() method, it has 6 overload version, you can choose one, this is the general approach

 

when it comes to Line, another way is using Point3d.GetDistanceTo()

a Line has StartPoint and EndPoint,abbr sp & ep.

if you want to check Point3d p, then:

d1=p.GetDistanceTo(sp);

d2=p.GetDistanceTo(ep);

length=theLine.Length;

if

A:d1+d2==length

or

B:|d1-d2|=length

thus we assume p is on the line,case A means p is on the line, case B means p on the extend, see image below:

CX_0331_110831.jpg

Valued Contributor
HelloWorlddd
Posts: 87
Registered: ‎05-03-2013
Message 4 of 5 (117 Views)

Re: How to determine a point on one line

03-31-2014 04:21 AM in reply to: cdinten
Thank you very much, it's a easy way.
Valued Contributor
cdinten
Posts: 61
Registered: ‎11-19-2010
Message 5 of 5 (114 Views)

Re: How to determine a point on one line

03-31-2014 04:24 AM in reply to: HelloWorlddd

it should be. it is both easy to understand in mathematics and to convert this idea to code.

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