Does anyone know how to rotate a geodesic dome so that the split line is exactly on the XY plane?
Geodesic_Rotate.gh (10.8 KB)
Geodesic_Rotate.gh (10.8 KB)
I wonder if it is not something like
DEGRES(ATAN((1+(5)^0.5)/2))
Icosaedron coordinates are calculated like that
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The “split line”? There are multiple “split lines” that divide the sphere in half.
If you just start with your initial icosahedron oriented so a pair of opposite vertices are mirrors wrt XY, then your split line will automatically stay on XY when you subdivide/project.
geodesic_orient.gh (11.8 KB)
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I’d used the parakeet plugin to generate the geodesic and it was oriented like this to begin with!
But thanks, that’s the logical way of doing this. How did you generate your icosahedron?
Sorry, i should have explained that better, It’s maybe obvious if you’ve played with geodesic domes before… If you look at the dome there are obvious planes that split it in half without splitting existing triangles…
That’s the right angle I think!
Obviously. More than one.
P.S. It’s hard to explain the methods I used to determine this but if you rotate the “sphere” in the XZ plane by 31.7175 degrees, you get one.
Is that 90-(Laurent’s answer)?
Laugh if you like but never underestimate the power of brute force. 
The purple group determines the rounded segment lengths: 27.327 and 30.902. Dispatch separates them into long (‘A’) and short (‘B’) segments. The planar polylines use the long segments. Rotating them in XZ plane and looking at ‘Front’ view, it was easy to see by inspection that something close to 32 degrees was the answer.
The rest projects midpoints of the rotated long segments to the XY plane and measures the distances, sorting them, etc. Answer: 31.7175 degrees.
Geodesic_Rotate_2023Mar2a.gh (24.9 KB)
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