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    [Plugin] Center of Gravity

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    • sketchartist023S Offline
      sketchartist023
      last edited by

      Hello TIG and others,

      I have a question about the COG. I tried using it to get the COG information for a plane design and it only created a grouped stack of planes on Z axis top to bottom of the solid. I used a simple square solid and same effect. Here is a pic of what it creates. Not sure what I am looking at but I do find this useful too for other ideas Im working on for crafting lol.

      Using: Sketchup v8 (i know....google version but I like it)
      P.S. I did have this working once before, years ago.

      Thanks if you can help 😄


      TIGcogPlugineffect.png

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      • TIGT Offline
        TIG Moderator
        last edited by

        It might be a v8 incompatibility: see here: https://sketchucation.com/forums/viewtopic.php?p=630803#p630803
        Please ensure you are using the latest [compatible] version [perhaps copy it from your last working v8 Plugins folder ? I did PM you an older version at the start of this year ? I re-PM it if I can find it...].

        Also run it with the Ruby Console open and report all of the error messages you get...

        TIG

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        • T Offline
          TommyWoodbury
          last edited by

          Awesome plugin, thanks TIG! Any plans on making it 2019 compatible?

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          • Dave RD Offline
            Dave R
            last edited by

            It works just fine in SketchUp 2019. And in SketchUp 2020.

            Here's an example done in SU2020.
            Screenshot - 5_28_2020 , 7_15_31 AM.png

            Etaoin Shrdlu

            %

            (THERE'S NO PLACE LIKE)

            G28 X0.0 Y0.0 Z0.0

            M30

            %

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            • M Offline
              Mare99
              last edited by

              Hi, thanks for this plug-in, this is what I was looking for! But it dodn't work for me. I do everything like in your video but mistake "Selection NOT 2 C of G Groups!".
              I am sure that I have two Groups (see in apdx). I try do the same with two Components and there is mistake : "Selection is NOT group!".
              What I do bad? I have Sketchup 2018.
              Thank you for help!
              Jirka


              Capture-22.jpg

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              • TIGT Offline
                TIG Moderator
                last edited by

                @Mare99

                Are you sure that the selection is of two groups of CofG text?
                Select one and look at Entity Info...

                If you have copied one it'll report as two versions of the same thing...

                The geometry should be unique instances, as should the text group...

                Please edit one of them, make no changes and then close it immediately - this will have the affect of making the two into unique versions - perhaps that's the issue and it'll fix it...

                I just tried it and it works OK - provided that they are two unique things...

                If not, than please post a simple SKP containing them and I'll investigate further...

                TIG

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                • Dave RD Offline
                  Dave R
                  last edited by

                  From the screen shot it looks like you are selecting the geometry groups, not selecting the CofG groups as the instructions indicate.
                  Screenshot - 11_13_2020 , 1_29_00 PM.png

                  Screenshot - 11_13_2020 , 1_29_16 PM.png

                  Etaoin Shrdlu

                  %

                  (THERE'S NO PLACE LIKE)

                  G28 X0.0 Y0.0 Z0.0

                  M30

                  %

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                  • A Offline
                    antuan
                    last edited by

                    Great job TIG, really useful plugin. I have a doubt, though. When there are many nested groups/components but all of them are made from the same material so density is constant across all of them, (e.g. a piece of furniture made from same wood) can the plugin directly find the COG of the final group containing all subgroups/subcomponents? Or should I find COG of every object separately and join them toghether with "Composite COG" tool?
                    In the overview of the plugin is explained that you can select "a group of groups" and in fact I see that I can select the outer object and I get a result, but then the calculated weight is wrong, sometimes just a bit, others almost double than real, depending on the model. And if that matters, as far as I know all subcomonents/subgroups are solids. I don't know if this is because the plugin is not intended to work this way or it is because of a model issue or any other mistake in my workflow. Thanks in advance for your help.
                    Antonio

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                    • A Offline
                      antuan
                      last edited by

                      Hi again, I will add an example of what I asked in my last post.

                      In this model I have copied twice the same group, made out from 7 subgroups/subcomponents (all of them solids, with a volume I can see in the entity info).

                      If I select the "group of groups/components" (right) and run CoG I obtain a weight of 38kg.

                      If I run CoG for each of the subgroups or subcomponents separately and then run Composite CoG from the obtained CoG entities, (left) I obtain a weight of only about 13 kg.

                      What is the reason for that? Can't this plugin be used for a group of groups, even if the density is the same for all of them?

                      Thank you for any help you can give me.

                      Antonio


                      CoG differences.png

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                      • TIGT Offline
                        TIG Moderator
                        last edited by

                        If the selected group is a solid then it's straightforward to find its volume and the only convolution is the 'slicing' of the form to calculate its CofG.
                        But a collection of solids does not form a solid - look at 'entity info' to confirm this.
                        A solid contains only geometry, and that needs to be suitably set up.

                        You can select a number of solids [best copied to the side] and then simply combine them into a single solid using the Solid Tools 'Union' command.
                        If the parts all have the same density then the returned CofG volume and weight should be correct and the Combined CofG is not needed at all...

                        TIG

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                        • robertWanR Offline
                          robertWan @TIG
                          last edited by robertWan

                          @TIG Should I look for an older version or is there any way to make it work in 8.0 Pro?CoG.png

                          TIGT 1 Reply Last reply Reply Quote 0
                          • TIGT Offline
                            TIG Moderator @robertWan
                            last edited by TIG

                            @robertWan
                            v8 is very old, and unsupported by many newer extensions, but CofG should work with it...
                            It appears the '.round()' function isn't working...
                            I don't have that version installed to test it...
                            I can't find an earlier version without the round code in it...
                            You could try editing the RB file with Notepad++ so the
                            lines#379 to #390, which read

                            dp=4
                            volume=0
                            ###
                            ### convert it to units matching density...
                            while volume == 0
                            	volume=(vol * 0.000016387064).round(dp) if @units=~/\/m3/
                            	volume=(vol * 16.387064).round(dp)      if @units=~/\/cm3/
                            	volume=(vol * 0.000021433471).round(dp) if @units=~/\/yd3/
                            	volume=(vol * 0.000578703704).round(dp) if @units=~/\/ft3/
                            	dp+=1
                            end
                            dp-=1
                            

                            becomes this edited version to avoid any arguments for the round method.

                            #dp=4
                            #volume=0
                            ###
                            ### convert it to units matching density...
                            #while volume == 0
                            	volume=(vol * 0.000016387064).round if @units=~/\/m3/
                            	volume=(vol * 16.387064).round if @units=~/\/cm3/
                            	volume=(vol * 0.000021433471).round if @units=~/\/yd3/
                            	volume=(vol * 0.000578703704).round if @units=~/\/ft3/
                            	#dp+=1
                            #end
                            #dp-=1
                            

                            restart SketchUp and see if that helps...

                            TIG

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                            • robertWanR Offline
                              robertWan @TIG
                              last edited by

                              @TIG said in [Plugin] Center of Gravity:

                              restart SketchUp and see if that helps...

                              CoG1.png

                              Unfortunately it didn't help.

                              Robert

                              TIGT 1 Reply Last reply Reply Quote 0
                              • TIGT Offline
                                TIG Moderator @robertWan
                                last edited by

                                @robertWan

                                I missed some 'dp' variables [sorry]

                                line#393
                                change

                                volTxt = sprintf("%.#{dp}f", volume)
                                

                                to read

                                volTxt = sprintf("%.4f", volume)
                                

                                line#409
                                change

                                weight = (volume * @density).round(dp)
                                

                                to read

                                weight = (volume * @density.round)
                                

                                and line#417
                                change

                                weightTxt = sprintf("%.#{dp}f", weight)
                                

                                to read

                                weightTxt = sprintf("%.4f", weight)
                                

                                I think that's all of them !!

                                TIG

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                                • robertWanR Offline
                                  robertWan
                                  last edited by

                                  CoG2.png
                                  Works!
                                  I am extremely grateful.
                                  Thank you.

                                  Robert

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