topic Convert list of 3d points to 2d points? in .NET Forum

Convert list of 3d points to 2d points?

Anonymous — Tue, 29 Dec 2009 07:40:49 GMT

Hi. I am using this to convert a list of 3d points to 2d points (z=0.0), and was wondering if there was a simpler way:

{code}
List<Point3d> my3dPoints = new List<Point3d>();
// added points to above
List<Point2d> my2dPoints = new List<Point2d>();
foreach( Point3d pnt in my3dPoints )
my2dPoints.Add( pnt.Convert2d( new Plane() ) );
{code}

Thank you.

{code}

Re: Convert list of 3d points to 2d points?

Anonymous — Tue, 29 Dec 2009 08:08:18 GMT

This may not come out right because the Autodesk discussion group software mangles code (isn't that just wonderful?).

{code}

List pnt3dList = new List();

// add items to pnt3dList

List pnt2dList = pnt3dList.ConvertAll( p => new Point2d( p.X, p.Y ) );

{code}

For a simple conversion (e.g, Z = 0.0), don't use Convert2d()
because it transforms the input point into the plane argument.
It's more efficient to just return a new Point2d.

Also, if your list of points is logically a set (e.g., no two elements
are coincident) and not order-dependent, you should probably
use a HashSet rather than a List.

In that case, you can use the Linq Select() method just like the
ConvertAll() method is used on the List example above:

{code}

HashSet points3d = new HashSet();

HashSet points2d = new HashSet(
points3d.Select( p => new Point2d( p.X, p.Y ) ) );

{code}

--
http://www.caddzone.com

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Supporting AutoCAD 2000 through 2010

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Email: string.Format("{0}@{1}.com", "tonyt", "caddzone");

wrote in message news:6309926@discussion.autodesk.com...
Hi. I am using this to convert a list of 3d points to 2d points (z=0.0), and was wondering if there was a simpler way:

{code}
List my3dPoints = new List();
// added points to above
List my2dPoints = new List();
foreach( Point3d pnt in my3dPoints )
my2dPoints.Add( pnt.Convert2d( new Plane() ) );
{code}

Thank you.

{code}

Re: Convert list of 3d points to 2d points?

Anonymous — Tue, 29 Dec 2009 08:26:33 GMT

I see that Tony has answered you,

but you may also want to have a look at this
discussion.

title="http://www.theswamp.org/index.php?topic=31404.0 CTRL + Click to follow link"
href="http://www.theswamp.org/index.php?topic=31404.0">http://www.theswamp.org/index.php?topic=31404.0

Topic: lambda expression to convert
lists

Regards

Kerry Brown

"rebar0" wrote in message
title="news:6309926@discussion.autodesk.com CTRL + Click to follow link"
href="news:6309926@discussion.autodesk.com">news:6309926@discussion.autodesk.com...

Hi.
I am using this to convert a list of 3d points to 2d points (z=0.0), and was
wondering if there was a simpler way:

{code}
List<Point3d>
my3dPoints = new List<Point3d>();
// added points to
above
List<Point2d> my2dPoints = new List<Point2d>();
foreach(
Point3d pnt in my3dPoints )
my2dPoints.Add( pnt.Convert2d( new Plane() )
);
{code}

Thank you.

{code}

Re: Convert list of 3d points to 2d points?

Anonymous — Tue, 29 Dec 2009 18:38:41 GMT

Ouch!!!!!

If one needs to convert a list of TInput to a list of TOutput, why would they use ForEach() rather than ConvertAll() ?

If you look at the implementation of ConvertAll() with Reflector, you might note that it sets the initial capacity of the result
list to the size of the input list, which is something one should always do when the number of elements they're working with is
known, to avoid the need for the list to incrementally reallocate its internal array each time it must grow in capacity.

For another thing, using ForEach() that way also breaks a fundamental rule of FP, that would effectively prevent it from being
easily parallelized.

BTW, ConvertAll() can thought of as a functional equivalent to AutoLISP's (mapcar) when used with only a single list argument.

--
http://www.caddzone.com

AcadXTabs: MDI Document Tabs for AutoCAD
Supporting AutoCAD 2000 through 2010

http://www.acadxtabs.com

Email: string.Format("{0}@{1}.com", "tonyt", "caddzone");

"Kerry Brown" wrote in message news:6309941@discussion.autodesk.com...
I see that Tony has answered you,
but you may also want to have a look at this discussion.
http://www.theswamp.org/index.php?topic=31404.0
Topic: lambda expression to convert lists

Regards
Kerry Brown

"rebar0" wrote in message news:6309926@discussion.autodesk.com...
Hi. I am using this to convert a list of 3d points to 2d points (z=0.0), and was wondering if there was a simpler way:

{code}
List my3dPoints = new List();
// added points to above
List my2dPoints = new List();
foreach( Point3d pnt in my3dPoints )
my2dPoints.Add( pnt.Convert2d( new Plane() ) );
{code}

Thank you.

{code}