Sketchup, Pepakura, Inkscape, Gimp, et al...

Discussion in 'Gallery & Designs' started by bclemens, Feb 13, 2008.

  1. bclemens

    bclemens Member

    Scaling issues...

    Well, I began the first beta-build of the sundial design


    and the trouble started immediately. I'm still dealing with the issue of scaling each component correctly. I began by constructing the hexagonal base and found that the development of the side did not match the top and bottom.


    As I built the base, I had to split the side and create extra space between the joints- you can see the white edges in the picture above.

    Also the round bottom of the stand was too small to fit snugly in the recess of the hexagonal base. These problems come from the fact that as I split components off the original design in Sketchup to be unfolded in Pepakura, I end up with several parts that were unfolded separately, and Pepakura makes them different sizes. I then have to rescale the 2-D developments as bitmaps in Inkscape.

    To try to solve this problem I had placed a 1 inch square in each Sketchup component I exported to Pepakura. This square then ended up on the 2-D development and I could use that as a reference when rescaling the bitmap in other programs. But I can see now that this small 1 inch square is not accurate enough to keep the scaling consistent with multiple portions of the model across several bitmaps.

    I will now try placing an 8 1/2 by 11 inch plane in all my Sketchup exports. This will then allow me to scale each 2-D bitmap based on the size of my final paper print-out. Perhaps this will give me the resolution I need to accurately produce components that fit well.


    Here are the base and stand such as they are. This was not easy for me to build! The way I designed the part will need to be redone to make the assembly easier and more accurate.



    I am beginning to see that the designer needs to keep many things in mind- aesthetics, buildability, engineering, which parts need to go on first, where to put the tabs for best results, fit and finish, etc.

    If nothing else, this experience continues to make me feel very humble when I see the fine designs members of this forum produce and when I see the fine models that are available commercially. Well, back to the drawing board ;)

  2. bclemens

    bclemens Member

    Beta Builders Wanted!

    I have rescaled and redesigned the sundial base...

    I have been thinking that it would be great to have other modelers help in the development of the components of new designs. In that spirit, I have the base development here:

    and an exploded drawing of the assembly here:

    If anyone would like to print it out and build it and give me feedback on the results, it will be greatly appreciated. I will be doing that as well, but I figure if more than one person is involved, it will result in better um...results.

    If you would be so kind as to post your feedback here regarding fit, ease of assembly, and any other issues, I will be very pleased.

    Everyone who helps in this way will be acknowledged in the documentation of the final product. This could be a great collective way to design and produce a model.

  3. RyanShort1

    RyanShort1 Member

    Here's my current project:


  4. CJTK1701

    CJTK1701 Banned

    This is all fantastic information and I would like to thank you, again, for this. I'm going through the process slowly, but surely as time allows.:thumb:

    Thank again.
  5. bclemens

    bclemens Member

    Pepakura Scale Isue solved...

    I believe I have hit on the most efficient way to ensure that a model which is unfolded piece-by-piece in Pepakura keeps the correct scale across several files.

    When I export the part from Sketchup, I make sure there is an 8 1/2 by 11 inch rectangle exported with the part. (If you use a different paper size, simply choose a rectangle that matches the dimension of the paper).

    When I open the part in Pepakura, there is the rectangle in correct proportion to the part. When I unfold the part, the rectancle follows into the 2-D development.

    After I have done all the work I need to do to the development in the 2-D screen, I adjust the scale in Pepakura by trial and error until the 8 1/2 by 11" rectangle perfectly fits a page of its own. Then I can print directly from Pepakura and choose the page(s) to print that have the model and not print the scale rectangle.

    And if I export this development as a bitmap, I can scale it appropriately in whatever other program I use there based on the rectangle.

    So far this is the best way I can come up with to make sure all the parts fit in the finished model :mrgreen:. I did this last weekend with my re-designed sundial stand and it fit the base very well.

  6. CJTK1701

    CJTK1701 Banned

    Brilliant! Thanks again Bruce, for taking the time to put this tutorial together.:thumb:

    I've just been aprooved as an authorized "Waybe Beta Testor!" So, as soon as I can, I'll put up a tut on that.:thumb:
  7. bclemens

    bclemens Member

    Thanks- I've been sidelined lately from this thread while working on the Tug, but I've been applying everything that we've been discussing here on that project. So it does work.
  8. K_2

    K_2 New Member

    bclemens - if your parts are coming from the same 3D file, then you can set the scale, in pepakura, for each part.
    Fron the menu -> '2D pattern window' -> 'scale up/down development by specifying value'
    Enter a scale number (NOT assembled size) and use this for all your parts.

    I always have a text file in my project folder telling me what i have done and what i have left to do, i always write the scale number in it so i don't forget.

    Nice sundial, how tall is it again?
  9. lriera

    lriera Member

    I agree. It is a very helpful step by step. Please keep showing us your way of work. Thank you.
  10. bclemens

    bclemens Member

    Thanks, K_2- I learned this fact a while back. I think Lex pointed out how to re-scale in Pepakura, but then I worked out that instead of rescaling by a "model size" value, which is ambiguous when you are dealing with files of individual components as parts of a larger whole, you can rescale by a "scale factor" which is consistent for the entire model.

    For example I learned that all my component files for the tug fit if I rescaled them to a factor of 23.31. So although the components all came from individual Sketchup files, the same scale factor applied to all of them.

    This is a great thing- that way you can save individual components from your overall Sketchup design in files of their own instead of putting all your "eggs into one basket" so to speak.

    The Yak 15 that I am working on now has a Pepakura scale factor of 25.33.


    so as of now, the approach I am taking goes something like this:
    1. design model in Sketchup
    2. break it out into individual components (or group of components), and save each component or group in Sketchup with an 8 1/2 inch by 11 inch rectangle
    3. export the file as a Google Earth .kmz file
    4. open Pepakura and import the file.
    5. unfold it (no tabs) and fix any issues with the zipper and rotate tool
    6. rescale the component and move the 8 1/2 x 11 rectangle onto a separate page, verifying that the scale is correct and the rectangle fits the page exactly
    7. move all parts of the component onto the first page. Now you are left with 2 pages in the 2-D development- the first page with the parts and the second page with the rectangle.
    1. export the file as a high resolution vector bitmap and specify one .bmp per page.
    2. explore to the folder where the bitmaps are and delete the second page of that component- I don't need the rectangle any more.
    3. open Inkscape and import the .bmp of the component
    4. resize the .bmp to fit the 8 1/2 by 11 page in inkscape, and position the .bmp into a layer of its own
    5. create another layer and trace the component parts in that layer using the Bezier pen, add tabs, part numbers, colors, and other details. In this layer you can also import .bmps for component texturing. This is what I did for the turbine blades below:
    1. save the finished file in the native Inkscape format (.svg), as well as a bitmap (.png) and an Adobe Acrobat file (.pdf)
    2. import the .png into Gimp for additional rendering (airbrush) or other image manipulation.
    3. Upload the final file as a .pdf for all the world to grab :thumb:
    Lots of work goes into one of these things! It's great that most of these programs are free- but you make up for the cheap cost in effort overhead. It would be great if there was one program that provided all this capability.
    Thanks for all the interest everyone is showing in this thread!

    P.S. K_2, the sundial is, as of now, about a foot tall. I think I will rescale it smaller in the end. Cathy told me I should build several to use for gifts when the Christmas holidays arrive, so the pressure's on!
  11. K_2

    K_2 New Member

    Still not sure why you use the rectangle if you enter the scale directly, but if it helps then that's fine with me. I used to do it myself.
    And holy cow - you got gimp to work :) never, ever upgrade it, it'll stop working forever.

    Keith - gone to look for inkscape.
  12. SCEtoAux

    SCEtoAux Member

    Bruce, I did a quick build of the sundial base. It seemed to go together pretty good. Just a few houskeeping sugestions on the print out since some of the straight lines are jagged and some of the sawtooth tabs on part 5 do not meet on the part. Also the tab at the end of part 5 seems to have a double line. Do you intend to leave parts 3,4,7, and 8 as butt joints? They posed no problem for me, but some might find them intimidating.

    I built it from the top down.
    1. I first cut out the parts (putting a GPS locator on parts 7 & 8 in case they decided to go on walkabout :mrgreen:).
    2. Glued part 5 into a cylinder and gued it to the bottom of part 1, aligning the holes.
    3. Glued part 6 into the hexagon shape then glued it to part 1.
    4. Glued parts 7 & 8 to part 5 with the 90° angle oriented correctly.
    5. Glued parts 3 & 4 to parts 1,6,7, & 8.
    6. Glued part 2 to the bottom of part 6.
    Something I forgot to do when glueing parts 7 & 8 to part 5 was to make sure they were aligned with opposite vertices. Nothing bad, though, since the angle of the long side stays the same and parts 3 & 4 glued on to them OK.

    I built a bowstring equatorial sundial out of wood and brass many years ago. It looked kind of like the paper one you are designing. The angle was fixed for a latitude of 32°N. Your idea of including a means to adjust the angle of the gnomon for different latitudes is good. :thumb:
  13. bclemens

    bclemens Member

    Thanks so much for your effort and input on the sundial! I'll go over your notes and incorporate changes that they point out. I'll get back to you via PM in more detail after I have done so since I don't have a thread started specific to the sundial.
    I'll also send you the files after it is completed as thanks.
  14. RyanShort1

    RyanShort1 Member


    I update GIMP every time and continue to be a very satisfied user...

  15. greasecup02

    greasecup02 New Member

    I've just started with sketchup your sucess gives me hope!
  16. bclemens

    bclemens Member

    Welcome, Danny. Good luck with the Sketchup!
    Keith, I guess the reason I still do the rectangle in each file is just as a "sanity check". It doesn't cost any more and it is a nice assurance that the piece will fit.

    Here's some progress on the Yak. The Sketchup plan followed by reality in cardboard:



    Looks a little like a fish skeleton at this stage :mrgreen:

    I can already see several changes that will be necessary- so beyond all the steps required in the design stage, the proofing stage requires you to test-build, modify, test-build, modify, document, test-build, on and on...

  17. Lex

    Lex Dollmaker

    Now that's a fine design! I'd love to see the skin on!!
  18. Dragos

    Dragos Active Member

    I also wait to see the result.
  19. eric_son

    eric_son Member


    Love those formers!

    How were you able to account for the thickness of the formers while you were modeling in 3d?

  20. lriera

    lriera Member

    Hi Bruce, me too I am following this thread with a lot of interest.

    Thank you.

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