[Plugin] Exploded Arc Centerpoint Finder UPDATE May 23, 2013
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I had not noticed that before, I don't use the point at center all that often. But it is true, it does not work on offset arcs. It is because the offset changes it from an ArcCurve entity to a simple Curve - which just means that SU no longer recognizes it as a true arc.
The ability to add a centerpoint to an arc is actually a plugin written by Google (@Last). So I went through and added the functionality to mine, then realized that it's actually just a plugin, so it would make more sense to change or modify their code.
But I need help here.
@Any Ruby Pro - My thinking is that I can alias their method that adds the centerpoint and essentially re-write it with my own code. And do this inside of this plugin. So when you run this plugin, it will install itself like normal, and also it will over-ride part of the contextmenu.rb example file (which is the ruby that adds the centerpoint funcitonality).
Is that the "correct" way to do it, so I don't actually re-distribute and re-write their file, but merely over-write in this script. Correct?
Chris
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Oh good...that sounds promising then. Could you potentially convert a simple curve to an ArcCurve? This way you would unlock the ability to increase segments in the entity info for an offset curve. Currently you cannot.
On another note regarding your great script. It will also find the centerpoint of a rectangle or square!! Just draw it out with the rectangle tool and then select two sides, run the script and it will mark the center! Great time saver!!
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truly a BIG help!, this is awesome!, THANKS!!
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@earthmover said:
Could you potentially convert a simple curve to an ArcCurve?
I think that TIG perhaps already created that plugin? Or maybe he created the first part of it and I was thinking I would use it to finish writing it....I don't recall anymore. But I agree, that would be handy. Not easy, maybe not even possible. But definitly handy!
Chris
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...TIG wasn't... but... what is you want to do take a Curve and make it into an ArcCurve ? For example you Weld together some Edges into a Curve and want them to become an ArcCurve ? This would only work if the original edges would form an Arc anyway - a Curve isn't necessarily even 2D let alone an Arc... Rather, don't you really want to select some Edges and make them into an Arc if it's possible to do so ?
Wouldn't it be more flexible [and quicker] to use Chris's tool to add a CentrePoint to what could be the Arc [from the Exploded Edge set], then place a Cpoint at a Vertex (or the two ends), Erase the Edges [or Erase them later ?] and simply redo an Arc/Circle using the points etc?
Can you give some better examples of where this might be useful [better/quicker] so I can see if the effort of making it work would be worthwhile...
I have already written a Method for changing Segments in an Arc http://forums.sketchucation.com/viewtopic.php?p=158903#p158903
It has an example script too: you select the Arcs to change, in the Ruby Console type changearcsegments 64 and they all have 64 segements [change number as desired]. It is like Entity Info in that you cannot change the Segments of Arcs forming complex 3D Geometry like cylinders... -
TIG,
Thanks for the response. I'm referring to offset arcs. When you offset an Arc, the result is a simple curve, which looses it's ability to increase segments,find center point from or take a radius dimension pull offs. In my work, I design a lot of radius steps, curved walls, curved walkway & Patios. I often will draw out an Arc, which represents a landing, then I will offset that Arc 5 or 6 times for my steps. By the time I get out the last offset, I may want to increase the segments in my arc as it is looking choppy, but it is not possible at that point. I'll also often delete the initial arc to open up my landing, then I'm left with all simple curves and I have no ability to find the center point, unless I explode a curve, use Chris's script, then reweld, but still it is not an Arc. I also tend to have trouble getting the weld ruby to work on certain exploded curves, and instead of welding, it will decimate it into more segments. The other thing is dimensioning. Only with an Arc can you use the dimension tool to get a quick radial dimension. If you try and get a dimension on a offset curve, it will just measure one of the segments and not the whole curve. This is where a conversion tool would be useful.
I noticed also, that when you have an Arc that is part of a face and extruded, it's extruded counterpart maintains it's Arc status, but both the initial Arc and the extruded Arc lose their ability to have to the segments changed, for obvious reasons. This would be important for trying to convert Curves to Arcs in 3D space, as the newly created Arc would have be locked similarly. The gain from converting a curve to an arc in 3D space would be solely the ability to pull radial dimensions and also to find center point. Unless someone wrote a script that would allow for selecting two arc counterparts in an extrusion and simultaneously increasing the segments in 3D after a curve to Arc conversion.
EDIT - I just looked at the link you posted. Sounds like my latter request was addressed in that post and not possible. Oh well then.
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Hey, EarthMover,
It was my request on this Google Group post that (partially?) inspired Chris F. to make his plugin. Using his idea from that discussion, I made code to find the center-point of two Edges... which I promply discarded when he made his implementation that didn't look like a train-wreck
So, I took his code (without permission; sorry, Chris!
) and made my own tool with a different interface (context menu) that I think adds (some of) the functionality you want. Since you probably wouldn't find it otherwise, here is the thread where I attached mine.The readme header in the file also explains how other coders can use the new methods for finding the center of a Curve or of any two Edges. I also wanted to add a radius method and the "convert Curve to ArcCurve" function discussed above, but they're still on the todo list. BTW, my plugin also works on Circles and Polygons.
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Hi Chris,
Arc Centerpoint Finder translated into French and the attached link http://biblio3d.1fr1.net/plug-in-sketchup-f19/plugin-arc-centerpoint-finder-en-francais-retrouver-le-point-central-d-un-arc-t448.htm#3004at the next
Christophe
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Great, thanks Christophe! I've updated the first post to also include a link to the French version.
Chris
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@chris fullmer said:
Name: Arc Centerpoint Finder
Version: v1.0wow! nice one.
perfect little timesaver.
thank you -
There's a wee bug. It adds the CPoint in model.entities instead of model.active_entities - so if you use this inside a group/component it's not added to the correct context.
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Chris, you're a mind reader...I was looking for this function for a long time. Thanks for your help in our sketchup's lives !!
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@thomthom said:
There's a wee bug. It adds the CPoint in model.entities instead of model.active_entities - so if you use this inside a group/component it's not added to the correct context.
Oh darn, there was a little while there where I think I forgot about .active_entities and just added everything to the .entities collection. I'll fix it and get it uploaded later today,
Chris
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ok, now updated so that when it is used in group/component edit mode, it will add the construction point inside the group that is being edited. Thanks for pointing that out Thom.
So re-download it from the first post in the thread.
Chris
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Thanks Chris,
I found this to be a very readable script for learning a little more Ruby. It's pretty clear from context what it's doing as far as finding a perpendicular direction, creating a temporary "z" from the original two edges, etc. I assume the ".cross" function is the Cross-product from vector algebra, which I vaguely remember, but I'll have to look up what that actually is and why it's called "cross".
Thanks again,
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i know it may seem stupid, but why can't i see the context "point at center" menu when i right-click on an arc?
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You have to first enable the sketchup ruby script examples from Window > Preferences > Extensions > Ruyb Script Examples (or might be the one called Utilities tools). Enable them both, then you should get the point at center option.
Chris
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@chris fullmer said:
You have to first enable the sketchup ruby script examples from Window > Preferences > Extensions > Ruyb Script Examples (or might be the one called Utilities tools). Enable them both, then you should get the point at center option.
Chris
ha!
i never knew this function came with SU.. i've been using jim f's arc_centerpoint.rb for a couple of years now.
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Hehe, and I wrote that before I realized Point at Center came with SketchUp!
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