Drawing Polygons by Apothem?

Catmando · 27 Dec 2010, 17:47

Hiya. I've been looking around on this forum for a certain plugin: a way to draw polygons by their apothem (the length of a line perpendicular to one of a polygon's sides, or in Sketchup terms, a line from the center point to the midpoint of an outer segment) instead of the radius. I searched this forum quite a bit and can't seem to find any mention of such a tool.

I know there is a fancy formula provided on Wikipedia for converting the radius length of a polygon to apothem, but it seems this forum loooves shortcuts (not that it's a bad thing ) and this would certainly help me and probably many others make stuff. Thanks in advance!

Also: if this is the wrong forum, I apologize. I am a newbie and this subforum's description says you can ask a question here.

mitcorb · 28 Dec 2010, 02:20

I don't know of such a tool.
Do I understand that you wish to generate a 2D polygon using a script that utilizes the apothem as a parameter?
May I ask why you do not wish to use the native Sketchup tool for polygons, aside from the possibility that it does not employ the apothem?
You can draw any polygon, make it a group, draw its apothem inside the group, measure the length, edit the value control box display and Sketchup should rescale the group proportionally to the desired apothem value.
Is this too much work? Even with tools, ya still gotta do some knitting.

Catmando · 28 Dec 2010, 04:23

@mitcorb said:

I don't know of such a tool.
Do I understand that you wish to generate a 2D polygon using a script that utilizes the apothem as a parameter?
May I ask why you do not wish to use the native Sketchup tool for polygons, aside from the possibility that it does not employ the apothem?
You can draw any polygon, make it a group, draw its apothem inside the group, measure the length, edit the value control box display and Sketchup should rescale the group proportionally to the desired apothem value.
Is this too much work? Even with tools, ya still gotta do some knitting.

I could do all that. I think I'd be better off with a tool to do it, though. I'm sorry to hear that there is no such tool. I guess I can manage, right? Thanks!

mitcorb · 28 Dec 2010, 12:15

Just to be clear:
I indicated that I do not know of such a tool.
That is not to say that it does not exist.
Someone may see this thread who does know.

EDIT: Oh, and thank you for teaching me a new word. I read more about it on several sites.

Dave R · 28 Dec 2010, 17:51

I don't know of a plugin for this, either but I can see that it could have its uses. When I need a polygon and I know the distance between flats but not the radius, I end up setting out two guidelines to help me draw it. It would be nice to be able to skip the guidelines, though.

mitcorb · 28 Dec 2010, 23:48

The apothem obviously would represent the radius of a circle inscribed within and tangent to the edges of the polygon. A line from polygon center to one of the vertices would be the radius of a circumscribed circle.
Autocad, I believe allows the construction either way, and probably some other cad programs.
Now, this makes me wonder if TIG's 2D tools or TIG's True Tangents could be helpful to you Catmando?

TIG · 29 Dec 2010, 00:20

You can already draw it using three similar Polygons and the built-in inferencing - see this example...

Catmando · 29 Dec 2010, 19:46

@tig said:

You can already draw it using three similar Polygons and the built-in inferencing - see this example...[attachment=0:2d3mez6r]PolyApothemExample.PNG[/attachment:2d3mez6r]

Wow! Clever trick there. I'll try that later. Thank you.

Jim · 31 Dec 2010, 16:33

I think several of the built-in tools could use some enhancements. It would be nice if the circle tool could be dragged to set the normal, for example. The line tool could use a double-line, and line-from-center modes. Rectangle too could be made to create rotated rectangles, etc. There's plenty of room for improvement. I had the thought to re-implement all the basic tools in Ruby adding some of these enhancements, but it's a big job.

Jean Lemire · 3 Jan 2011, 15:41

Hi folks.

See attached SU file for ideas.

Polygon drawn by Apothem.skp

brhildebrandt · 15 Aug 2011, 17:12

@tig said:

You can already draw it using three similar Polygons and the built-in inferencing - see this example...[attachment=0:2r6hvnb8]PolyApothemExample.PNG[/attachment:2r6hvnb8]

I just tried this trick and it is very quick and easy to do.

Thanks!

hburns · 14 Apr 2016, 19:49

Simple when drawing the geometry hit the ctrl key and it will switch to the circumscribed or Apothem method.

Dave R · 14 Apr 2016, 19:51

@hburns said:

Simple when drawing the geometry hit the ctrl key and it will switch to the circumscribed or Apothem method.

Yes. It is simple since SketchUp 2015 was released. Prior to that and when this thread was active, SketchUp didn't have this option as a native feature.