Recently, I stole something precious from a friend. I was sitting in Andy’s office, and there it was. An interesting shape. Three rings nestled inside each other. They could rotate independently, but if any translated, the others would follow. I had to have these rings.

So, I stole them. Well, I stole the idea of them. Andy still has his rings. I took the stolen idea, went to Madeup, and coded up the rings.

I started with a function that generated a spherical shell, a larger sphere with a slightly smaller sphere subtracted away from it:

You can’t tell it’s hollow unless you switch to wireframe.

Then I added two more spherical shells. You won’t be able to see those either, since they’re concentric, so I won’t share that step. But then I added two square dowels around the top and bottom of these spheres:

These dowels overlapped the sections of the spheres I did not want. So I subtracted them:

And I had my rings. They rotate independently:

Now I just need to get these printed in stainless steel. Or gold, with which I could pay back Andy.

Subtract shapes is very powerful. Does Madeup have union (add or + ?) and difference (intersection)?

I did these rings using an App called 123D Design by Autodesk on iPad. It is now the TinkerCad. I did by trial and error about the height of rings so with their curvatures the inner rings will not fall out. I wonder how the height of rings can be calculated.

Animation is cool. Madeup is getting versatile..

The animated rings have more sides. I have also changed the nside to 32 for the rings and exported as STL. I will print them using my Little Monster 3D printer later. If successful, I will bring one to you.

The animation was done in Blender. I’m unlikely to add animation to Madeup. I’m concerned that it will erode its focus on modeling.

Meshes can be joined with - for differencing, and for intersection, and or for unioning. I use a library called libigl to do the heavy-lifting of these operations, which in turn uses a library called CGAL.

Thanks for the libel and CGAL info. There seems to have some javascript clones but are not complete. On web/html5 platform, javascript can do the union, interest and difference, link in OpenJSCAD https://openjscad.org

## Comments

Subtract shapes is very powerful. Does Madeup have union (add or + ?) and difference (intersection)?

I did these rings using an App called 123D Design by Autodesk on iPad. It is now the TinkerCad. I did by trial and error about the height of rings so with their curvatures the inner rings will not fall out. I wonder how the height of rings can be calculated.

Animation is cool. Madeup is getting versatile..

The animated rings have more sides. I have also changed the nside to 32 for the rings and exported as STL. I will print them using my Little Monster 3D printer later. If successful, I will bring one to you.

The animation was done in Blender. I’m unlikely to add animation to Madeup. I’m concerned that it will erode its focus on modeling.

Meshes can be joined with

`-`

for differencing,`and`

for intersection, and`or`

for unioning. I use a library called libigl to do the heavy-lifting of these operations, which in turn uses a library called CGAL.Thanks for the libel and CGAL info. There seems to have some javascript clones but are not complete. On web/html5 platform, javascript can do the union, interest and difference, link in OpenJSCAD https://openjscad.org

I made a x3d version of the animation, may not be of interest of this site though. https://vrmath2.net/VRM2/html/testSphereSegment2.html