topic Re: "center of gravity" of a AcDbPolyLine in ObjectARX Forum

"center of gravity" of a AcDbPolyLine

Anonymous — Wed, 15 Oct 2003 23:20:28 GMT

Hello,

I am not a mathematician. Has anybody a algorithm to calculate the "center
of gravity" of a closed Polyline ?

Regards

Robert

Re: "center of gravity" of a AcDbPolyLine

Anonymous — Thu, 16 Oct 2003 01:22:49 GMT

"Robert Nihl" wrote in message
news:7F1FE3B716E28CDFBB75DF2BEB9B2307@in.WebX.maYIadrTaRb...
> Hello,
>
> I am not a mathematician. Has anybody a algorithm to calculate the "center
> of gravity" of a closed Polyline ?
>
> Regards
>
> Robert
>
>

Hi,

gx = ( x0 + x1 + ... + xn ) / n

n - numVerts

x0...xn - x coordinates of the polyline vertexes

And apply the same formula for gy and gz.

Regards,

Bogdan

Re:

Anonymous — Thu, 16 Oct 2003 01:22:49 GMT

> gx = ( x0 + x1 + ... + xn ) / n
> n - numVerts
> x0...xn - x coordinates of the polyline vertexes
>
> And apply the same formula for gy and gz.
>

That is much easier as I expected 🙂

Thanx

Robert

Re:

Anonymous — Thu, 16 Oct 2003 05:06:46 GMT

Hi, Bogdan!
You wrote to newsgroup Thu, 16 Oct 2003
02:22:49 -0700:
B> Hi,
B>
B> gx = ( x0 + x1 + ... + xn ) / n
B>
B> n - numVerts
B>
B> x0...xn - x coordinates of the polyline vertexes
B>
B> And apply the same formula for gy and gz.

It's not exactly for polyline with arc segments!

Best Regards,
Alexander Rivilis

Re:

Anonymous — Thu, 16 Oct 2003 08:33:08 GMT

Agree, I've written the answer without thinking at arcs.
Also, there is another error in my previous post: the last x value should
have the indices n-1.
If the polyline has arc segments an AcDbRegion could be made from the
polyline and use getAreaProp(...) method to find the centroid of the region.

Regards,
Bogdan

"Alexander Rivilis" wrote in message
news:6B4BBFFCC6B30EA3AC5F59D91EB82205@in.WebX.maYIadrTaRb...
> Hi, Bogdan!
> You wrote to newsgroup Thu, 16 Oct 2003
> 02:22:49 -0700:
> B> Hi,
> B>
> B> gx = ( x0 + x1 + ... + xn ) / n
> B>
> B> n - numVerts
> B>
> B> x0...xn - x coordinates of the polyline vertexes
> B>
> B> And apply the same formula for gy and gz.
>
> It's not exactly for polyline with arc segments!
>
> Best Regards,
> Alexander Rivilis
>
>