centre for scaling curve

For the purpose of scaling, is there a component that can find the centre point of any polygon?

Please see below quote.

component (Curve > Analysis > Centre) which gives me the centre of the circles. By
connecting it to the you can see that all circles would rescale in their level without movement. - Quote from Khabasi

Replies to This Discussion

Permalink Reply by Benjamin Golder on October 25, 2009 at 9:52am

The area component works fine if the polygon is closed and planar.

Permalink Reply by Vicente Soler on October 25, 2009 at 10:23am

If it's not planar or closed, you can find it yourself by extracting the polygon vertices, separating their x,y,z values, finding the arithmetic mean for each of the 3 lists of numbers (using the mean component) and constructing a new point with the resulting 3 values.

Permalink Reply by Anthony Dahu Mumagi on October 25, 2009 at 11:26am

thanks very much,

the polygon is not planar,

how do I extract the vertices is it 'curve>analysis>explode' component and how do I seperate their x,y,z values?

thanks

Permalink Reply by Vicente Soler on October 25, 2009 at 11:47am

To extract the vertices you can use the Divide Curve component set to 1 segment and the split at kinks option enabled. To separate the x,y,z values use the Decompose component.

Permalink Reply by Anthony Dahu Mumagi on October 25, 2009 at 12:30pm

Hi Vicente, the triangle on left of picture is the curve I am trying to make a point at centre of, the definition on right is what I have tried but does not seem to be working.?????

Permalink Reply by taz on October 25, 2009 at 1:05pm

Looks like Vicente took off...

But you should be working with points (not vectors) and you'll want to find the arithmetic mean (AM) of the x, y and z components to then construct the centroid.

Alternatively if all your polygons are triangles (I'm not sure from your screengrab...) which are always planar you can create a surface to find the centroid.

-taz

Permalink Reply by Anthony Dahu Mumagi on October 25, 2009 at 4:01pm

taz - awesome thanks very much!!

Permalink Reply by Vicente Soler on October 25, 2009 at 6:06pm

Thanks for filling in. Btw, haven't you heard of spherical triangles? :P

Permalink Reply by Anthony Dahu Mumagi on October 26, 2009 at 5:22am

hi, I think the question was not to me but anyway the polygons were not all triangles in this case.

Permalink Reply by Alexis Schneider on November 17, 2010 at 9:27am

What a great strain guys. I am finding this very helpful. I am trying to do the same thing for hexagons. Could you fill me in as to what the third operation is above? What is the green line with the arrow above it?

a

Permalink Reply by David Rutten on November 17, 2010 at 11:14am

Here's another one, it computes the average of all the corners in a polyline (or just a list of points really). Mass addition on all the points, then divide by the number of points you have. Basically the regular Average formula:

A + B + C + D + E + ... + Z
────────────────────
N

--
David Rutten
david@mcneel.com
Seattle, WA

Attachments:

polyline average.ghx, 44 KB

Permalink Reply by taz on November 17, 2010 at 12:40pm

When you shatter a closed curve the start and end verticies are the same. The green line with the arrow is [Shift List]. With the default shift settings (S=1, Wrap=False) the end point drops off so the same vertex isn't being counted twice.