Addon: Creating a basket arch in Blender

Recently I was thinking about a visualization of some rooms in our house. These rooms were once separate but the wall has been broken through and the arch between them has a very specific form: a basket arch, aka three centered arch. This is a form widely used not only indoor but also for example for many 17th century bridges and is not entirely trivial to construct as it involves matching three circle segments at their tangents. So I constructed a small addon to create basket arches ;-)

Availability and possible improvements

The addon is available on GitHub. You can install it in the usual way: File->User preferences->Addons->Intall from file. Don't forget to check the 'enable addon' box. It will the be available from the Add Mesh menu in the 3D view.

The addon constructs what is called a classical three centered arch, that is you can only choose the width while the height has then a fixed proportion. It might be a good idea to add the variant where you can also specify the height, which will give a squeezed arch that is has not quite the same shape as a classical arch that is scaled in the z-direction.

Currently the vertices in the arch a distributed with more or less even spacing along the circle. Because we use the angle along a circle segment the last vertex may or may not touch the ground. This is however hardly visible and since I intended this addon for visualization rather than CAD I thought i good enough. I might fix it though in the near future.

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