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    Method for drawing an antiprism with equilateral sides

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    sketchup
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    • S Offline
      sketchup_roolz
      last edited by

      http://img813.imageshack.us/img813/9940/240pxsquareantiprism.png

      Link Preview Image
      Square antiprism - Wikipedia

      favicon

      (en.wikipedia.org)

      I can easily create a version of this by rotating the top face of a cube by 45° and tweaking a few lines.
      However the resulting triangles are not equilateral, which is what I'm after.

      Any ideas?
      Thanks

      *PS
      Anyone know a way to construct polygons in SketchUp starting only with their "Nets".
      Without knowing the specific folding angle I haven't been able to do this precisely.

      http://img683.imageshack.us/img683/2056/netz.png
      *

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      • TIGT Online
        TIG Moderator
        last edited by

        Try thisantiprism.PNG

        TIG

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        • pilouP Offline
          pilou
          last edited by

          seven decimals of ° 😲
          That is precision 💚

          Frenchy Pilou
          Is beautiful that please without concept!
          My Little site :)

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          • honoluludesktopH Offline
            honoluludesktop
            last edited by

            I think this is a way to do it without calculations, but because sketchup arcs are polygons, its impossible to do a perfectly accurate projection.Temp00.PNGI used a default arc (12 sides), if you did one with (say) 256 sides, you could get closer.

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            • TIGT Online
              TIG Moderator
              last edited by

              I didn't do calculations either [except for the angle that I added]...
              You'll need a Circle with 1000 sides and then just draw/group/copy/rotate stuff... see the 'Steps' illustration...
              [I removed the illustration here in favor the the 'steps' set - see the next few posts along...]

              TIG

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              • S Offline
                sketchup_roolz
                last edited by

                Thanks for the detailed reply Tig. 🤓

                Unfortunately I'm having trouble figuring out the proper sequence of steps to follow your instructions. 😳

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                • S Offline
                  sketchup_roolz
                  last edited by

                  Hey what happened to all those steps you wrote out Tig? 😉

                  Anyway I guess the circle approximation is the best we can do...

                  Thanks everyone

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                  • TIGT Online
                    TIG Moderator
                    last edited by

                    Here's an improved version of the StepsantiprismSteps.PNG
                    It works for any size 'cube'...

                    TIG

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                    • D Offline
                      dedmin
                      last edited by

                      TIG - This Is Google

                      🎉 🎉 🎉

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                      • TIGT Online
                        TIG Moderator
                        last edited by

                        Much easier 😒antiprism2d.PNG

                        TIG

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                        • S Offline
                          sketchup_roolz
                          last edited by

                          Thanks Tig. You're a genius. 😎

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                          • S Offline
                            sketchup_roolz
                            last edited by

                            woops! 😳

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                            • TIGT Online
                              TIG Moderator
                              last edited by

                              @sketchup_roolz said:

                              Not that anyone cares anymore but here's a my proper 2D method...
                              http://img573.imageshack.us/img573/272/68861221.png

                              I fixed your faulty link...
                              An interesting alternative approach... 😄
                              I am thinking how it might get converted to an 'algorithm'...
                              Which must be possible as it involves 45/30/15 degree triangles with known side length...
                              Sleeping on it now... 😉

                              TIG

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                              • S Offline
                                sketchup_roolz
                                last edited by

                                Not that anyone cares anymore but here's a my proper 2D method...

                                http://img573.imageshack.us/img573/272/68861221.png

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                                • S Offline
                                  sketchup_roolz
                                  last edited by

                                  Very clever Jeff. 🤓

                                  Much appreciation for all the hard work here.
                                  I don't really have a practical need to get this level of precision/accuracy but problems like this totally consume me.
                                  I figured the faster I could figure it out it the sooner I could move on to more important things! (or not)

                                  SketchUp is an amazing piece of software and maybe one day I'll have a more concrete use for it. 💚

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                                  • pilouP Offline
                                    pilou
                                    last edited by

                                    Why anybody save the SKP file "save as SU6"?
                                    Like this anybody can reload easily any file! 😄

                                    Frenchy Pilou
                                    Is beautiful that please without concept!
                                    My Little site :)

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                                    • pilouP Offline
                                      pilou
                                      last edited by

                                      PS :How many triangles must have the polyedra?
                                      On the first post there are 8 on "the plan"
                                      On the Xray Tig volume there are 7 ! 😮

                                      @unknownuser said:

                                      Won't the file lose some of its v7, and v8 features. Did v6 have "dynamic components", etc.?

                                      there are rarelly dynamic component in "hard geometry" like in this post or exotic functions 😄

                                      Frenchy Pilou
                                      Is beautiful that please without concept!
                                      My Little site :)

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                                      • honoluludesktopH Offline
                                        honoluludesktop
                                        last edited by

                                        @unknownuser said:

                                        Why anybody save the SKP file "save as SU6"?
                                        Like this anybody can reload easily any file! 🙂

                                        Won't the file lose some of its v7, and v8 features. Did v6 have "dynamic components", etc.?

                                        Btw, am I sticking my foot in my mouth? I didn't read all of the posts.

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                                        • jeff hammondJ Offline
                                          jeff hammond
                                          last edited by

                                          @unknownuser said:

                                          Why anybody save the SKP file "save as SU6"?
                                          Like this anybody can reload easily any file! 😄

                                          oops, i try to remember to do this prior to uploading at scf but i just forget sometimes 😄
                                          i added a v6 file to my earlier post

                                          dotdotdot

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                                          • honoluludesktopH Offline
                                            honoluludesktop
                                            last edited by

                                            ???????????

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