Uniform Distribution on a Sphere Example 3D

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Uri_dolphin3 Uri Wilensky (Author)

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Model was written in NetLogo 3D 4.1pre7 • Viewed 780 times • Downloaded 26 times • Run 0 times
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WHAT IS IT?

This code example demonstrates the correct way to uniformly distribute turtles on the surface of a sphere. Note that simply setting the heading and pitch to random numbers between 0 and 360 results in a non-uniform distribution with clustering at the poles in the z direction. The solution in SETUP-UNIFORM is based on information found here:

http://mathworld.wolfram.com/SpherePointPicking.html

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to setup-uniform
 ca
 crt number
 [
   ;; remember that turtles automatically have a random heading when created
   tilt-up asin (1.0 - random-float 2.0)
   jump max-pxcor
   roll-right random-float 360
 ]
 do-plot
end 

to setup-not-uniform
 ca
 crt number
 [
   ;; remember that turtles automatically have a random heading when created
   tilt-up random-float 360
   jump max-pxcor
   roll-right random-float 360
 ]
 do-plot
end 

to do-plot
  set-current-plot "xcor"
  set-current-plot-pen "xcor"
  histogram [ xcor ] of turtles
  set-current-plot "ycor"
  set-current-plot-pen "ycor"
  histogram [ ycor ] of turtles
  set-current-plot "zcor"
  set-current-plot-pen "zcor"
  histogram [ zcor ] of turtles
end 


; Copyright 2007 Uri Wilensky. This code may be freely copied, distributed,
; altered, or otherwise used by anyone for any legal purpose.

There are 3 versions of this model.

Uploaded by When Description Download
Uri Wilensky over 12 years ago Updated from NetLogo 4.1 Download this version
Uri Wilensky over 12 years ago Model from NetLogo distribution Download this version
Uri Wilensky over 12 years ago Uniform Distribution on a Sphere Example 3D Download this version

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