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I'm trying to make a model of a building out of cardstock to use as background for some of my miniatures, I want to have a corridor with a vaulted ceiling butts which up against a curved wall.

How do I measure the curve of the wall (Vertical cylinder in the image below), and then draw it out on to a flat piece of card (Horizonal shape), so that when I bend the card round it fits perfectly?

The curve to cut it highlighted in red.

enter image description here

I'm only using the 3D image as an example, this is going to be real world hand craft.

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  • I'm looking for a way to do this by hand. Something that I can show people how to do for themselves in a class, for example; Aug 13 at 18:30

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During the middle part of the last century, I had a mechanical drawing class, even though I had not yet reached high school. One of the skills taught in that class was the development of drawing the intersection of two bodies. I believe this question qualifies in that regard.

Just about any drawing program will work for your objective. One can use a CAD program with which one is familiar. I use Inkscape (free, multi-platform) but also LightBurn, a laser application (paid, multi-platform) but any line drawing software will do the trick.

If one has access to precise, accurate drafting equipment (T-square, drafting table, triangles), one can also do this manually.

The key factor is to have orthographic views of the model. If your model is in a contemporary 3D modeling program (Meshmixer?), you can set the views and use a screen capture to create the orthographic images.

A YouTube video presents the overall concepts and practice of drafting such a project. I used "manual method drawing cylinder intersections," even though one of your objects is not a cylinder. It would have been far too challenging to determine proper terminology for the hemi-cylindrical shape engaging the cylinder in the image provided.

The results of the search are consistent with what little I recall from so many decades past. In your project, you'd end up with a drawing of a rectangle representing the face-on view of the cylinder with an arched rectangle centered in the rectangle.

Because the result of a rectangle represents a squared view of the cylinder, there's a perspective loss, although I'm not sure I'm using the right terms.

I changed the search to "sheet metal drawing intersecting cylinders" and discovered a more comprehensive result.

Wikisource provides a series of problems and solutions similar to your objective:

Right Angle T-Joint projection

Combining the above video with this Wikisource information may give you the background necessary to accomplish your goal.

If you've created the model, knowing the program in which it was created may be useful.

Additionally, Pepakura (not-free, not expensive) provides for "unfolding" an STL file and may be the fastest and easiest option, considering the amount of work required to CAD out or hand draw your project.

Another program for Windows, Ultimate Unwrap 3D runs US$50 - $60 depending on version. The home page graphics indicate that it would provide a similar result:

Ultimate Unwrap screen shot

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  • Great answer, but when I say "Model", I'm thinking cardstock and glue. The kind of things that you'd use for a Warhammer game. Rather than a 3D rendered model. Aug 13 at 18:34
  • Yes, that was my understanding. You have to have a paper template from which to cut the pieces used to assemble the model. The above dissertation is directed to that end. Also, it isn't necessary to have a 3D model. If one can sketch orthographic views in the classic CAD manner, the above non-computer methods apply.
    – fred_dot_u
    Aug 13 at 18:35
  • Also, one can create a 3D model in a simplistic manner with a program such as TinkerCAD if one chooses to travel the computer method path.
    – fred_dot_u
    Aug 13 at 18:39
  • I'm looking for a 100% offline method. No computer involved. Aug 13 at 18:50
  • That leaves you with the legacy method, which isn't all that difficult or complex. I figure if I learned how to do it in the 6th grade, it must have been easy enough. Too many years have passed since that time, though.
    – fred_dot_u
    Aug 13 at 19:46

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