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Re: random points near central point

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fir <profesor.fir@gmail.com> writes:

> środa, 19 lipca 2023 o 21:24:09 UTC+2 Ben Bacarisse napisał(a):
>> fir <profes...@gmail.com> writes: 
>> 
>> > i need tos et asteroids in game (about 100 or 200) but not in square 
>> > area with two rands one for x and second for y but need it to 
>> > be sphericel symetric around central point and in more densitu near it 
>> > and less desity with bigger radius until some radius when it is zero
>> If you just pick a uniform angle and a uniform radius and plot those 
>> points, the density of points near the origin will be higher. This is a 
>> very simple method and might be suitable for a game.
>
> uniform  radius? dont know what is that

Uniform refers to a statistical distribution with uniform density --
every result in some range is equally likely.  Your random number
generator will have a function to give you a number uniformly
distributed in some range (often >= 0.0 to < 1.0).  I'll use drand48()
as an example.

  double pi = 4 * atan(1);
  double r = drand48();
  double a = 2 * pi * drand48();

Now if you plot the point at angle a and distance r from (0,0) you will
see that they all lie in the unit circle but they cluster round the
origin.

Obviously you can convert polar coordinates r and a to Cartesian x and y
with

  double x = r * cos(a), y = r * sin(a);

I'm not sure if this is what you want, but it sounds like it from some
of the words you used.

-- 
Ben.

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random points near central point fir <profesor.fir@gmail.com> - 2023-07-18 23:38 -0700
  Re: random points near central point Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-07-19 01:49 -0700
    Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-19 04:20 -0700
  Re: random points near central point Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-07-19 01:59 -0700
  Re: random points near central point Kaz Kylheku <864-117-4973@kylheku.com> - 2023-07-19 16:50 +0000
  Re: random points near central point Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-07-19 20:23 +0100
    Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-20 09:31 -0700
      Re: random points near central point Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-07-20 20:42 +0100
        Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-20 12:56 -0700
          Re: random points near central point Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-07-20 20:59 +0100
          Re: random points near central point David Brown <david.brown@hesbynett.no> - 2023-07-21 09:13 +0200
            Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-21 05:55 -0700
              Re: random points near central point Ed Prochak <edprochak@gmail.com> - 2023-07-22 12:24 -0700
                Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-23 04:04 -0700
                Re: random points near central point Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-07-23 14:53 +0100
                Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-23 07:03 -0700
                Re: random points near central point "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-07-23 12:30 -0700
                Re: random points near central point Ed Prochak <edprochak@gmail.com> - 2023-07-30 21:48 -0700
        Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-20 13:20 -0700
      Re: random points near central point "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-07-20 12:57 -0700
        Re: random points near central point fir <profesor.fir@gmail.com> - 2023-07-20 13:18 -0700
          Re: random points near central point "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-07-23 12:28 -0700
  Re: random points near central point "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-07-20 12:56 -0700

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