Name: Arc Centerpoint Finder Version: v1.0 SU Version: Developed on SU 7, should be compatible with 6 and 5 at least. Description: This scipt places a construction point at the centerpoint of an arc, even after the arc has been exploded in SketchUp. Usage: Select two line segments that used to be part of an arc object in SketchUp. Then run the plugin from Plugins>Chris Fullmer Tools> History: 1.0: 2009-05-11
If you run into situations where it doesn't work, and you're pretty sure it should work, please let me know. EDIT: Sorry the video is so quiet! You might need to turn up your speakers a little.
And its available in French now too! Find it HERE!
Chris 552
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I'm guessing you've figured out how to analyze co-planer segments to determine if they have ARC (and probably circle) attributes. If, so could you use the code to reconstruct/convert them back into "real" SU arcs or circles?
Another, cool thing would be to recognize say a circle that had been scale along one axis to make an ellipse, then pick its center point or rescale back into a circle or display its radius.
Thanks again Chris. I have run into the problem of trying to find center points of exploded arcs many, many times. Thanks for this very useful solution!!!
Hi Mitcorb, yes it will automatically put itself into the CF tool set in the plugins menu. I have done that on all my scripts because I found that I was clogging up the plugins menu rather quickly. So now they all load themselves into the CF sub menu.
Hi Dave, yes it will work on segments that are not connected in any way. I think the only requirement is that the segments are coplanar.
Also, it should be noted that it will return bad points sometimes. Specifically, if you are using 2 segments that are not the same length, that will lead to a center point being added that is probably not really the centerpoint of the arc. It relies on the line segments being equal in length. I could build another check into it so that it checks that first if that would be helpful.
Hmmm coulda sworn it was a Takamine because mine has the same body profile and your bridge seems to have the same tapered profile as mine. I did a so-so model of mine, but I did not render it. And now I think I will try to attach a skp of the furniture I modeled using your new tool. This is not my design and some of the components and connections are not precise. But, as some kind of tribute to your capabilities, see attachment. I apparently cannot attach the skp. I will try to do a jpg.
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I take the slow, deliberate approach in my aimless wandering.
By the way, Chris: On your reply to Dave, is there any reason to limit the number of segments to two? It would seem that the more coplanar segments, the more precision. Maybe not. Here again, I have no real understanding of the Ruby language. That tool saved me a ton of time, because the upper backrest section was done with it, but the lower section webbing was copied one element at a time and individually rotated and spaced. The dadblamed model is 3.99 MB!
I used Tube Along Path for the round sections, follow me on the elliptical tube frame, Fredo Freescale bend tool on the curved work, native pen and pushpull on the rectangular sections. I knew it was going to be a fat file, but I wanted to do it anyway.
I take the slow, deliberate approach in my aimless wandering.
If it is a true arc, 2 segments are just as precise as 3 or 3,000. So no need to worry, 2 segments is all it needs. I could add the ability to select lots of connected line segments and have it attempt to find all their centerpoints. But that would take considerably more time. Its a script I've discussed with someone else, and maybe in time it will happen. But for now, this is all it is, but its still pretty useful.
@John, the idea of revuilding exploded arcs is a good one, and I thought it would be easy to accomplish. But it actually takes more work than I realized it would. I think its possible, but I'm not 100% sure yet. I'll add it to my list of scripts I'd like to work on. I seriously need to start a list like that....
I need to find centre-points so frequently that an icon would be useful. Would that be possible?
I raised the issue of a proper lathing tool in a previous thread, but no one took on the challenge. Using follow me when lathing produces exploded arcs and circles. It would be extremely useful to have a tool that would lathe a shape about an axis but produce edges that were proper circles or arcs.
Chris, this is an interesting plugin and I caan see a lot of possibilities. I was just playing around with it using a randomly drawn Bezier curve. Below are the results. The curve with the guidepoints is the result of finding the centers for the 1st & 11th segments, the 2nd & 12th, 3rd & 13th and so on. The straight line comes from the centers of the 1st & 20th segments, the 2nd & 19th, 3rd & 18th and so. There must be some sort of progression in the distances between points but I didn't take the time to figure that out. I don't know if that sort of thing has much usefulness but I thought it was an interesting result to find while getting my first cup of coffee injected into my system.
Bezier Centers.jpg
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Inspecting mirrors is a job I could easily see myself doing.
Hehehe, oops! Line 42 does have problems. I should fix that and update it. Thanks for pointing it out. I'm sure if you look closely you'll find lots of other places that could be improved.
Good luck on your script. You'll make a lot of friends around here if you get that up and running!
I'm very late in thanking you for this plugin: literally hundreds of times I've had to re-create the centerpoint of a curve that, in the process of manipulation, has "lost" its centerpoint.
A perfect example of a plugin that saves a lot of time.
thomthom wrote:That's because Chris mixes his plugins with crack cocaine making everyone addicted.
Hey, Thom, cut that out: if they arrest him how will we get any more of his great plugins
"If you don't plan ahead you'll be at the mercy of those that do" - Ashleigh Brilliant
Hi Chris I just want to say thank you for making such wonderfully useful tools for the SU community. I was thinking maybe I will start to learn Ruby one of these days. For someone who have had no experience with any programing language where would you recommend that I start?
I missed this one too. Something I always need as well. Thanks a ton Chris!
A designer is an emerging synthesis of artist, inventor, mechanic, objective economist and evolutionary strategist. - R. Buckminster Fuller Some of my 3D crap
@Bob - Great, glad it has been helpful so often. Thanks for posting here to let me know
@Adam - Great, hope it helps you out!
@Chango - Thanks also for the kind words. They go a long way! As for learning Ruby, I say go for it. I think Ruby is the perfect language to learn. I have VERY little programming background. I understood the concept of if then ele statements, but that was about it. I found Ruby to be very nice to work with. And writitng SketchUp tutorials is something I've been doing for so long, so I recently put together 2 tutorials on Ruby for Sketchup. The first one is here:
It does not teach much Ruby syntax, but it does point you to a good tutorial that will help teach Ruby in general. Then my tutorial explains how to use Ruby with SketchUp to write plugins. Hopefully its helpful. I just started with Ruby in January and I have learned a TON from the great authors here on the forum. They are all very helpful.
So I would suggest taking a look at that tutorial. See how far you get, come back here with questions. I think there are ALWAYS good ideas for scripts around here if you need some ideas for own once you get the basic syntax worked out. Good luck with it and ask lots of questions.
Quick question. One thing I've always wondered about was why an offset arc loses it's ability to find a centerpoint. Any way to add a centerpoint function in your script to arcs that are the result of an offset, without having to explode the curve and select two segments?
A designer is an emerging synthesis of artist, inventor, mechanic, objective economist and evolutionary strategist. - R. Buckminster Fuller Some of my 3D crap
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?
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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A designer is an emerging synthesis of artist, inventor, mechanic, objective economist and evolutionary strategist. - R. Buckminster Fuller Some of my 3D crap
for this very helpful plug in and again for all the others- a very impressive collection of time savers. 
