[chimerax-users] sphereFactor interpolation

[Tom Goddard]

Hi James,

  The "sphere factor" parameter in the ChimeraX "shape icosahedron" command

	https://www.cgl.ucsf.edu/chimerax/docs/user/commands/shape.html#icosahedron

allows making a surface that is part way between an icosahedron and a sphere.  Sphere factor of 0 gives an icosahedron with its 60 flat triangular facets.   Sphere factor of 1 gives a sphere.  A sphere factor of 0.5 moves every icosahedron surface point half way radially towards a sphere that has the same radius as the icosahedron (ie the corners of the icosahedron lie on the sphere).  You can use any linear interpolation value for the sphere factor including negative values and values greater than one and they produce some pretty shapes as shown in the image below.

	Tom

Sphere factor values  -8, -4, -2, 0, 0.5, 1, 1.2, 1.5, 2.



> On Jul 4, 2022, at 4:55 PM, James Hodgkinson-Bean via ChimeraX-users <chimerax-users at cgl.ucsf.edu> wrote:
> 
> Hi
> 
> I have been playing around with developing some scripts that can measure sphericity directly from input icosahedron virus models. 
> 
> The scripts are working well, however my sphericity measurement is currently not represented as a relative scale between an icosahdron (sphericity = 0) and a sphere (sphericity = 1) as appears the case in chimeraX. I wondered if you could possibly tell me the equation used in ChimeraX to interpolate this scale when generating icosahedral shapes with variable sphericalFactor?
> 
> Apologies if this question is to complex for a simple quick answer; I'm a first year PhD student and am new to making such calculations. If it's too complicated I'm sure I can figure it out myself. 
> 
> 
> Cheers, 
> James. 
> 
> 
>  
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