Difference from Geodesic Chord Charts

[Ryan Jarvis]

Hello!

I've been playing with the code for the last few days and I noticed a discrepancy while taking some notes.   

I've traditionally used Chord factor chartswhen constructing these shapes in the real world (i.e. www.domerama.com/calculators/chord-charts/).   When I run ` ./geodesic -c 1 -f X ico | ./off_query El -d6` the edge values differ for the 3V sphere and higher.  (1V and 2V match the values on this site)

My understanding that these are computed in similar ways (radius of 1, get the central angle of the vertex and then `2*sin (<central_angle>/2)`).   I'm obviously missing something.  Would anyone be kind enough to point out how antiprism differs from these traditional chord charts?

Thanks!

[Adrian Rossiter]

Hi Ryan

The Antiprism geodesic models are all calculated using a single
method, and the aim is only to make a symmetric geodesic polyhedron.

Chord charts for builders can be tailored to make building easier.
They might be designed to include a small circle that the dome can
sit on, or they might be designed to include fewer strut lengths, etc.

Another source of difference, is that the geodesic vertices which are
interior to the original faces are calculated from, for example, the
intersection of three lines that don't mutually intersect, but intersect
in pairs as three close points that need to be converted to a single
vertex in the geodesic model. There is more than one way to do this. In
Antiprism, the geodesic vertex is the centroid of these three
intersections projected onto the sphere.

Adrian.
--
Adrian Rossiter
adr...@antiprism.com
http://antiprism.com/adrian

[Ryan Jarvis]

Thanks for the fast reply!  I'll report back here if any other info arises.