Re: [ESPResSo] bug in random.tcl in mbtools

[Markus Deserno]

Hi,

the discussion for how to draw numbers equidistributed
on the surface of the sphere has been recently discussed
on the Espresso list.  Torsten has corrected a previously
biased version somewhere else in the code.  Let me remind
you how it's done:

1. Draw a random number z equidistributed between -1 and 1.
2. Draw a random number f equidistributed between 0 and 2 pi.
3. Calculate r := sqrt(1-z^2)
4. Then the following triplet (x,y,z) is a point on the unit
   sphere picked from a uniform distribution on that sphere:
   x = r cos(f)
   y = r sin(f)
   z

Best,

Markus

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Dr. Markus Deserno
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