# How can I make a sphere filled exactly by 3 smaller spheres?

I want to make a procedural model of a sphere (size user defined) which then is filled by a user defined number of smaller spheres - and the sizes of the smaller spheres filling the big one is automatically adjusted when the number of smaller spheres changes.

With "filled" I mean tangent spheres.

I thought it would be an easy one to do with geo nodes - but no.

Thank you very much, everyone!

(The sketch is hugely simplified, to an emberrassing extent. :) )

This is what happens with GRANT's first approach:

• hello, this would be easier to visualize with a diagram :) Mar 13, 2023 at 20:19
• True! I will add one. Thanks! :)
– PdW
Mar 13, 2023 at 20:54
• If it is mathematically possible at all to tangentially place 3 spheres of equal radius inside a bigger sphere, I'm sure the equation is available somewhere Mar 13, 2023 at 21:05
• Right?? That's what I thought. It seems very possible to me...
– PdW
Mar 13, 2023 at 21:30
• Maybe this can help ? i.sstatic.net/IGVrY.png Mar 14, 2023 at 7:24

Is this what you're looking for?

You can convert a sphere mesh to volume in geometry nodes, and then scatter points in that volume using a grid. You can set the spacing factor, and use that spacing factor to drive the radius of each of your smaller spheres so that they're always edge to edge. That way, changing the radius also changes the number of instances inside the sphere.

• Grant, thank you, it looks that could could be it. Let me test it real quick. Be right back.
– PdW
Mar 13, 2023 at 21:32
• Grant, this is almost it! Incredible. The only thing missing: it does not go below 4 small circles. 3 is actually what I was looking for the most. If it's getting a little more inner spheres, they do not seem to distribute in a natural way. I will post a screenshot including the geo node, in case I did sth. wrong there. Your help is greatly appreciated!
– PdW
Mar 13, 2023 at 21:57
• @PdW Actually I cannot get it below 8 spheres (not circles), as soon as I increase the radius a little more then they are gone completely... Mar 14, 2023 at 8:12
• Yes, it was a very good start from Grant. Maybe someone will bring this to the final stage. Thank you very much, everyone!
– PdW
Mar 14, 2023 at 14:53