.NET

## .NET

Valued Contributor
Posts: 87
Registered: ‎05-03-2013
Message 1 of 5 (181 Views)

# How to determine a point on one line

181 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*
Posts: 2,077
Registered: ‎04-29-2006
Message 2 of 5 (168 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
Posts: 61
Registered: ‎11-19-2010
Message 3 of 5 (120 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:

Valued Contributor
Posts: 87
Registered: ‎05-03-2013
Message 4 of 5 (105 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
Posts: 61
Registered: ‎11-19-2010
Message 5 of 5 (102 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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