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quick & easy random dir vector, how?

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  quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-30 13:47 -0700
    Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-30 13:56 -0700
      Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-31 02:08 +0100
        Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 00:51 -0700
        Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-05-31 02:12 -0700
          Re: quick & easy random dir vector, how? Eli the Bearded <*@eli.users.panix.com> - 2019-05-31 19:27 +0000
            Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 12:49 -0700
              Re: quick & easy random dir vector, how? Eli the Bearded <*@eli.users.panix.com> - 2019-05-31 20:36 +0000
                Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 14:00 -0700
                  Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 14:19 -0700
        Re: quick & easy random dir vector, how? mark.bluemel@gmail.com - 2019-05-31 03:56 -0700
          Re: quick & easy random dir vector, how? queequeg@trust.no1 (Queequeg) - 2019-05-31 11:57 +0000
          Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-31 15:22 +0100
            Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 07:42 -0700
              Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 08:25 -0700
        Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-31 05:20 -0700
          Re: quick & easy random dir vector, how? Bart <bc@freeuk.com> - 2019-05-31 13:39 +0100
            Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-31 15:51 +0100
            Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-03 08:26 -0400
          Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-05-31 05:54 -0700
            Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-31 06:15 -0700
              Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 06:23 -0700
              Re: quick & easy random dir vector, how? David Brown <david.brown@hesbynett.no> - 2019-05-31 16:12 +0200
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-31 08:14 -0700
                  Re: quick & easy random dir vector, how? David Brown <david.brown@hesbynett.no> - 2019-05-31 18:18 +0200
                  Rick should killfile everybody. (Was: quick & easy random dir vector, how?) gazelle@shell.xmission.com (Kenny McCormack) - 2019-05-31 17:39 +0000
                    Re: Rick should killfile everybody. (Was: quick & easy random dir vector, how?) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-31 10:55 -0700
                      Re: Rick should killfile everybody. (Was: quick & easy random dir vector, how?) Bart <bc@freeuk.com> - 2019-05-31 22:33 +0100
                        Re: Rick should killfile everybody. (Was: quick & easy random dir vector, how?) Keith Thompson <kst-u@mib.org> - 2019-05-31 16:26 -0700
                          Re: Rick should killfile everybody. (Was: quick & easy random dir vector, how?) gazelle@shell.xmission.com (Kenny McCormack) - 2019-05-31 23:29 +0000
                        Re: Rick should killfile everybody. (Was: quick & easy random dir vector, how?) gazelle@shell.xmission.com (Kenny McCormack) - 2019-05-31 23:28 +0000
                  Re: quick & easy random dir vector, how? waterwitch86@gmail.com - 2019-06-09 03:47 -0700
              Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-31 15:43 +0100
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-05-31 08:13 -0700
                  Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-31 22:49 +0100
              Re: quick & easy random dir vector, how? Richard Damon <Richard@Damon-Family.org> - 2019-05-31 23:01 -0400
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-01 04:10 -0700
                  Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-01 13:47 +0100
                    Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 12:04 -0700
                      Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 12:35 -0700
                        Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 12:53 -0700
                      Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 14:52 -0700
                        Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 15:04 -0700
                          Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-01 15:41 -0700
              Re: quick & easy random dir vector, how? Anton Shepelev <anton.txt@gmail.com> - 2019-06-01 15:30 +0300
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 05:30 -0700
                  Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 05:39 -0700
                    Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-03 15:17 +0100
                      Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 07:32 -0700
                        Re: quick & easy random dir vector, how? David Brown <david.brown@hesbynett.no> - 2019-06-03 18:09 +0200
                        Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-03 21:14 +0100
                          Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 13:18 -0700
                            Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-03 22:42 +0100
                              Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 16:21 -0700
                        Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-03 15:40 -0700
                          Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-04 05:19 -0700
                            Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-04 16:31 +0100
                              Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-04 11:48 -0400
                                Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-04 21:09 -0700
                                  Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-04 21:11 -0700
                                Re: quick & easy random dir vector, how? jadill33@gmail.com - 2019-06-05 12:41 -0700
                                  Re: quick & easy random dir vector, how? jadill33@gmail.com - 2019-06-05 12:46 -0700
                                  Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-05 13:53 -0700
                                    Re: quick & easy random dir vector, how? Eli the Bearded <*@eli.users.panix.com> - 2019-06-05 21:45 +0000
                                      Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-05 23:06 -0700
                                        Re: quick & easy random dir vector, how? Eli the Bearded <*@eli.users.panix.com> - 2019-06-06 06:47 +0000
                                          Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-06 18:32 -0700
                                            Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-06 18:44 -0700
                              Re: quick & easy random dir vector, how? richard@cogsci.ed.ac.uk (Richard Tobin) - 2019-06-05 13:43 +0000
                                Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-06-05 07:24 -0700
                                  Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-05 13:29 -0700
                                Re: quick & easy random dir vector, how? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-06-05 08:05 -0700
                            Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-04 19:01 -0700
                            Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-06 22:57 -0400
                          Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-06 09:14 -0400
                            Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-06 08:10 -0700
                            Re: quick & easy random dir vector, how? "F. Russell" <fr@random.info> - 2019-06-06 16:17 +0000
                              Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-06 20:18 -0400
                                Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-06 23:22 -0700
                                  Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-07 07:15 -0700
                                Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-06-07 00:41 -0700
                            Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-09 13:57 -0700
                              Re: quick & easy random dir vector, how? Richard Damon <Richard@Damon-Family.org> - 2019-06-10 08:18 -0400
                                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-10 08:49 -0400
                                  Re: quick & easy random dir vector, how? Richard Damon <Richard@Damon-Family.org> - 2019-06-10 20:59 -0400
                                    Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-10 18:27 -0700
                                Rick is a Marine!!! (Was: quick & easy random dir vector, how?) gazelle@shell.xmission.com (Kenny McCormack) - 2019-06-10 13:53 +0000
                                  Re: Rick is a Marine!!! (Was: quick & easy random dir vector, how?) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-10 09:14 -0700
                              Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-10 07:24 -0700
              Re: quick & easy random dir vector, how? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-06-03 08:30 -0400
            Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 06:21 -0700
              Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 06:26 -0700
                Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 06:33 -0700
                  Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 07:00 -0700
                    Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 07:14 -0700
                      Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 10:15 -0700
                        Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 10:40 -0700
                          Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 14:01 -0700
              Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-05-31 07:07 -0700
                Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 07:15 -0700
    Re: quick & easy random dir vector, how? Anton Shepelev <anton.txt@gmail.com> - 2019-06-01 00:40 +0300
      Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-05-31 14:54 -0700
      Re: quick & easy random dir vector, how? Clifford Heath <no.spam@please.net> - 2019-06-02 23:00 +1000
        Re: quick & easy random dir vector, how? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-06-03 00:00 -0700
          Re: quick & easy random dir vector, how? Clifford Heath <no.spam@please.net> - 2019-06-03 17:33 +1000
            Re: quick & easy random dir vector, how? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-06-03 00:55 -0700
            Re: quick & easy random dir vector, how? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-06-04 10:00 -0700
    Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-01 18:34 -0700
      Re: quick & easy random dir vector, how? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-06-02 03:13 +0100
        Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-01 21:47 -0700
      Re: quick & easy random dir vector, how? Anton Shepelev <anton.txt@gmail.com> - 2019-06-02 13:16 +0300
        Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-02 05:38 -0700
          Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-02 05:54 -0700
            Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-02 06:08 -0700
              Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-02 06:24 -0700
                Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-02 06:34 -0700
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-02 06:43 -0700
                  Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-02 07:06 -0700
                    Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-02 13:12 -0700
                Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-02 06:58 -0700
                  Re: quick & easy random dir vector, how? gazelle@shell.xmission.com (Kenny McCormack) - 2019-06-02 14:08 +0000
                  Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-02 21:56 -0700
                    Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-02 21:56 -0700
                    Re: quick & easy random dir vector, how? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-06-03 02:47 -0700
                      Re: quick & easy random dir vector, how? "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-06-07 01:32 -0700
    Re: quick & easy random dir vector, how? "F. Russell" <frussell@random.info> - 2019-06-03 12:33 +0000
      Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-03 07:36 -0700
        Re: quick & easy random dir vector, how? "F. Russell" <frussell@random.info> - 2019-06-03 14:46 +0000
          Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-03 08:13 -0700
        Re: quick & easy random dir vector, how? fir <profesor.fir@gmail.com> - 2019-06-03 07:51 -0700

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#144242

fir:

> sometimes you want random int, but sometimes you need
> random dir vector in 3d space (by random dir i mean
> randomly directed and of length 1.00)
>
> how to generate it to be generated quick (sometimes i may
> need to generate tons of them so quick is important) and
> easy?

Consider an observer in the center of a sphere.  A random
point lies at a random asimuth, so choose

                    phi = Tau * [0,1] .

The elevation xi is more difficult because the amount M of
points at a certain elevation is proportional to the
circumference at this height, i.e.

                     M ~ Tau * cos xi ,

and so should be the probability of choosing a certain xi:

           P(xi) = cos xi => xi = arccos [-1,1] .

-- 
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#144245

W dniu piątek, 31 maja 2019 23:40:33 UTC+2 użytkownik Anton Shepelev napisał:
> fir:
> 
> > sometimes you want random int, but sometimes you need
> > random dir vector in 3d space (by random dir i mean
> > randomly directed and of length 1.00)
> >
> > how to generate it to be generated quick (sometimes i may
> > need to generate tons of them so quick is important) and
> > easy?
> 
> Consider an observer in the center of a sphere.  A random
> point lies at a random asimuth, so choose
> 
>                     phi = Tau * [0,1] .
> 
> The elevation xi is more difficult because the amount M of
> points at a certain elevation is proportional to the
> circumference at this height, i.e.
> 
>                      M ~ Tau * cos xi ,
> 
> and so should be the probability of choosing a certain xi:
> 
>            P(xi) = cos xi => xi = arccos [-1,1] .
> 
i think this topic can be closed (as they say in some trash stack overflow) - it is becouse some solutions was given, maybe not best but posiibly its not worth to stay here forever (i think some may add something but preferably if hhas something better than those two)

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#144288

On 1/6/19 7:40 am, Anton Shepelev wrote:
> fir:
> 
>> sometimes you want random int, but sometimes you need
>> random dir vector in 3d space (by random dir i mean
>> randomly directed and of length 1.00)
>>
>> how to generate it to be generated quick (sometimes i may
>> need to generate tons of them so quick is important) and
>> easy?
> 
> Consider an observer in the center of a sphere.  A random
> point lies at a random asimuth, so choose
> 
>                      phi = Tau * [0,1] .
> 
> The elevation xi is more difficult because the amount M of
> points at a certain elevation is proportional to the
> circumference at this height, i.e.
> 
>                       M ~ Tau * cos xi ,
> 
> and so should be the probability of choosing a certain xi:
> 
>             P(xi) = cos xi => xi = arccos [-1,1] .
> 

Can this be done more understandably using quaternions?
I suspect it can.

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#144321

Clifford Heath <no.spam@please.net> writes:

> On 1/6/19 7:40 am, Anton Shepelev wrote:
>
>> fir:
>>
>>> sometimes you want random int, but sometimes you need
>>> random dir vector in 3d space (by random dir i mean
>>> randomly directed and of length 1.00)
>>>
>>> how to generate it to be generated quick (sometimes i may
>>> need to generate tons of them so quick is important) and
>>> easy?
>>
>> Consider an observer in the center of a sphere.  A random
>> point lies at a random asimuth, so choose
>>
>>                      phi = Tau * [0,1] .
>>
>> The elevation xi is more difficult because the amount M of
>> points at a certain elevation is proportional to the
>> circumference at this height, i.e.
>>
>>                       M ~ Tau * cos xi ,
>>
>> and so should be the probability of choosing a certain xi:
>>
>>             P(xi) = cos xi => xi = arccos [-1,1] .
>
> Can this be done more understandably using quaternions?
> I suspect it can.

I don't think so.  Quaternions are just a particular representation
for a rotation in 3-space, or a way of representing an orientation
in 3-space if one wants to think of them that way.  Given a random
quaternion, it's easy to get a random direction vector out of it,
but similarly vice versa.  The two problems are almost identical -
it's hard to imagine a solution for one being especially easier
to understand than solving the other more directly.

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#144322

On 3/6/19 5:00 pm, Tim Rentsch wrote:
> Clifford Heath <no.spam@please.net> writes:
> 
>> On 1/6/19 7:40 am, Anton Shepelev wrote:
>>
>>> fir:
>>>
>>>> sometimes you want random int, but sometimes you need
>>>> random dir vector in 3d space (by random dir i mean
>>>> randomly directed and of length 1.00)
>>>>
>>>> how to generate it to be generated quick (sometimes i may
>>>> need to generate tons of them so quick is important) and
>>>> easy?
>>>
>>> Consider an observer in the center of a sphere.  A random
>>> point lies at a random asimuth, so choose
>>>
>>>                       phi = Tau * [0,1] .
>>>
>>> The elevation xi is more difficult because the amount M of
>>> points at a certain elevation is proportional to the
>>> circumference at this height, i.e.
>>>
>>>                        M ~ Tau * cos xi ,
>>>
>>> and so should be the probability of choosing a certain xi:
>>>
>>>              P(xi) = cos xi => xi = arccos [-1,1] .
>>
>> Can this be done more understandably using quaternions?
>> I suspect it can.
> 
> I don't think so.  Quaternions are just a particular representation
> for a rotation in 3-space, or a way of representing an orientation
> in 3-space if one wants to think of them that way.  Given a random
> quaternion, it's easy to get a random direction vector out of it,
> but similarly vice versa.  The two problems are almost identical -
> it's hard to imagine a solution for one being especially easier
> to understand than solving the other more directly.

I have so far failed to fully understand quaternions, but they represent 
a 4D space that folds into a 3D system without having the problems of 
"gimbal lock" that occurs in polar 3D systems.

"Directly overhead" is 90 degrees elevation, but what is the azimuth? 
Quaternions never need to ask that question. But perhaps the present 
issue doesn't present that problem anyhow.

Clifford Heath.

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#144324

On Monday, 3 June 2019 08:33:46 UTC+1, Clifford Heath  wrote:
> 
> I have so far failed to fully understand quaternions, but they represent 
> a 4D space that folds into a 3D system without having the problems of 
> "gimbal lock" that occurs in polar 3D systems.
> 
> "Directly overhead" is 90 degrees elevation, but what is the azimuth? 
> Quaternions never need to ask that question. But perhaps the present 
> issue doesn't present that problem anyhow.
> 
A quaternion is a 3D unit vector with a scalar attached, which represents
the rotation about the vector. So you have the same problem with
finding random quaternions as with random direction vectors. 

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#144413

Clifford Heath <no.spam@please.net> writes:

> On 3/6/19 5:00 pm, Tim Rentsch wrote:
>
>> Clifford Heath <no.spam@please.net> writes:
>>
>>> On 1/6/19 7:40 am, Anton Shepelev wrote:
>>>
>>>> fir:
>>>>
>>>>> sometimes you want random int, but sometimes you need
>>>>> random dir vector in 3d space (by random dir i mean
>>>>> randomly directed and of length 1.00)
>>>>>
>>>>> how to generate it to be generated quick (sometimes i may
>>>>> need to generate tons of them so quick is important) and
>>>>> easy?
>>>>
>>>> Consider an observer in the center of a sphere.  A random
>>>> point lies at a random asimuth, so choose
>>>>
>>>>                       phi = Tau * [0,1] .
>>>>
>>>> The elevation xi is more difficult because the amount M of
>>>> points at a certain elevation is proportional to the
>>>> circumference at this height, i.e.
>>>>
>>>>                        M ~ Tau * cos xi ,
>>>>
>>>> and so should be the probability of choosing a certain xi:
>>>>
>>>>              P(xi) = cos xi => xi = arccos [-1,1] .
>>>
>>> Can this be done more understandably using quaternions?
>>> I suspect it can.
>>
>> I don't think so.  Quaternions are just a particular representation
>> for a rotation in 3-space, or a way of representing an orientation
>> in 3-space if one wants to think of them that way.  Given a random
>> quaternion, it's easy to get a random direction vector out of it,
>> but similarly vice versa.  The two problems are almost identical -
>> it's hard to imagine a solution for one being especially easier
>> to understand than solving the other more directly.
>
> I have so far failed to fully understand quaternions, but they
> represent a 4D space that folds into a 3D system without having
> the problems of "gimbal lock" that occurs in polar 3D systems.
>
> "Directly overhead" is 90 degrees elevation, but what is the
> azimuth?  Quaternions never need to ask that question.  But
> perhaps the present issue doesn't present that problem anyhow.

I don't fully understand quaternions either.  To the extent that
I do understand them, my instinct tells me they aren't going to
be useful for this problem, mainly because they are tied to a
particular (orthonormal) coordinate system.  The choice of
coordinate system introduces some bias (or so my instincts lead
me to believe), which puts us back where we started of having to
compensate for the bias.  Only now I don't understand what the
bias is. :)

For better or worse, there are the fuzzy thoughts behind my
fuzzy understanding.

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#144280

On 5/30/2019 1:47 PM, fir wrote:
> sometimes you want random int, but sometimes you need random dir vector in 3d space
> (by random dir i mean randomly directed and of length 1.00)
> 
> how to generate it to be generated quick
> (sometimes i may need to generate tons of them so quick is important) and easy?
> 

An easy way is to create 3 random numbers from -1...1 and make sure you 
don't get all zeros. Set them to the x, y and z components of your 
vector, then normalize it. You now have a normalized vector pointing in 
a random direction. Is that good enough?

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#144281

"Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com>
writes:

> On 5/30/2019 1:47 PM, fir wrote:
>> sometimes you want random int, but sometimes you need random dir vector in 3d space
>> (by random dir i mean randomly directed and of length 1.00)
>>
>> how to generate it to be generated quick
>> (sometimes i may need to generate tons of them so quick is important) and easy?
>>
>
> An easy way is to create 3 random numbers from -1...1 and make sure
> you don't get all zeros. Set them to the x, y and z components of your
> vector, then normalize it. You now have a normalized vector pointing
> in a random direction. Is that good enough?

The result is not uniform.  You will get more directions pointing
(roughly) towards the corners of the cube than towards the middle of the
faces.

Have you not been reading the thread?

-- 
Ben.

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#144282

On 6/1/2019 7:13 PM, Ben Bacarisse wrote:
> "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com>
> writes:
> 
>> On 5/30/2019 1:47 PM, fir wrote:
>>> sometimes you want random int, but sometimes you need random dir vector in 3d space
>>> (by random dir i mean randomly directed and of length 1.00)
>>>
>>> how to generate it to be generated quick
>>> (sometimes i may need to generate tons of them so quick is important) and easy?
>>>
>>
>> An easy way is to create 3 random numbers from -1...1 and make sure
>> you don't get all zeros. Set them to the x, y and z components of your
>> vector, then normalize it. You now have a normalized vector pointing
>> in a random direction. Is that good enough?
> 
> The result is not uniform.  You will get more directions pointing
> (roughly) towards the corners of the cube than towards the middle of the
> faces.
> 
> Have you not been reading the thread?
> 

Ahh... Not really. Just thinking out loud. Sorry everybody.

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#144283

Chris M. Thomasson:

> An easy way is to create 3 random numbers from -1...1 and
> make sure you don't get all zeros. Set them to the x, y
> and z components of your vector, then normalize it. You
> now have a normalized vector pointing in a random
> direction. Is that good enough?

If will be random, but not enough :-)

-- 
()  ascii ribbon campaign -- against html e-mail
/\  http://preview.tinyurl.com/qcy6mjc [archived]

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#144285

Driving to work yesterday I was projecting from the origin out to linear
points on the unit square and realized what you all were talking about.

Makes sense.

-- 
Rick C. Hodgin

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#144286

W dniu niedziela, 2 czerwca 2019 14:39:04 UTC+2 użytkownik Rick C. Hodgin napisał:
> Driving to work yesterday I was projecting from the origin out to linear
> points on the unit square and realized what you all were talking about.
> 
> Makes sense.
> 
and where is the apology, stupidity maker?

to quite soem spaming idiot maker:

> Or maybe you naysayers will owe me a metaphoric apology. :-)
> We shall see.  The game is on! 

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#144289

On Sunday, June 2, 2019 at 8:54:50 AM UTC-4, fir wrote:
> W dniu niedziela, 2 czerwca 2019 14:39:04 UTC+2 użytkownik Rick C. Hodgin napisał:
> > Driving to work yesterday I was projecting from the origin out to linear
> > points on the unit square and realized what you all were talking about.
> > 
> > Makes sense.
> > 
> and where is the apology, stupidity maker?


Apologize for what, you bully?

fir, you are always hurting people with hate, meanness, and horrible
manners with no respect for anyone.  What a wretched way to exist.

I am very sad for you.  Your life's pain must hurt you tremendously.

-- 
Rick C. Hodgin

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#144290

W dniu niedziela, 2 czerwca 2019 15:08:29 UTC+2 użytkownik Rick C. Hodgin napisał:
> On Sunday, June 2, 2019 at 8:54:50 AM UTC-4, fir wrote:
> > W dniu niedziela, 2 czerwca 2019 14:39:04 UTC+2 użytkownik Rick C. Hodgin napisał:
> > > Driving to work yesterday I was projecting from the origin out to linear
> > > points on the unit square and realized what you all were talking about.
> > > 
> > > Makes sense.
> > > 
> > and where is the apology, stupidity maker?
> 
> 
> Apologize for what, you bully?
> 

for sharing stupidity stupid idiot

in your case apologization will not 
work (though would be obvious first step) 
becouse you wandalizing this group for long months and hundreds of live hours

also your kind of stupidity is kinda ultraheavy (far worse than common shalow stupidity which is more often seen)

and im not a bully stupid idiot, ikm a defendef of this group agains some stupid spamming brainles zomboid idiot which vandalizes it heavy for very long time





> fir, you are always hurting people with hate, meanness, and horrible
> manners with no respect for anyone.  What a wretched way to exist.
> 
> I am very sad for you.  Your life's pain must hurt you tremendously.
> 

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#144292

W dniu niedziela, 2 czerwca 2019 15:24:58 UTC+2 użytkownik fir napisał:
> W dniu niedziela, 2 czerwca 2019 15:08:29 UTC+2 użytkownik Rick C. Hodgin napisał:
> > On Sunday, June 2, 2019 at 8:54:50 AM UTC-4, fir wrote:
> > > W dniu niedziela, 2 czerwca 2019 14:39:04 UTC+2 użytkownik Rick C. Hodgin napisał:
> > > > Driving to work yesterday I was projecting from the origin out to linear
> > > > points on the unit square and realized what you all were talking about.
> > > > 
> > > > Makes sense.
> > > > 
> > > and where is the apology, stupidity maker?
> > 
> > 
> > Apologize for what, you bully?
> > 
> 
> for sharing stupidity stupid idiot
> 
> in your case apologization will not 
> work (though would be obvious first step) 
> becouse you wandalizing this group for long months and hundreds of live hours
> 
> also your kind of stupidity is kinda ultraheavy (far worse than common shalow stupidity which is more often seen)
> 
> and im not a bully stupid idiot, ikm a defendef of this group agains some stupid spamming brainles zomboid idiot which vandalizes it heavy for very long time
> 
> 
> 
> 
> 
> > fir, you are always hurting people with hate, meanness, and horrible
> > manners with no respect for anyone.  What a wretched way to exist.
> > 
> > I am very sad for you.  Your life's pain must hurt you tremendously.
> >

("defender" should be in some quitation marks, but this well known idiots makes people writing in some simplified language specially for idiots

its something liek "basic english" and "english" in my opinion this idiot provokes some answers made in that special kind ow writing more suitable for agggreviationing idiots - and thsi is one of numeroust faults/features of this moron)

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#144294

On Sunday, June 2, 2019 at 9:24:58 AM UTC-4, fir wrote:
> W dniu niedziela, 2 czerwca 2019 15:08:29 UTC+2 użytkownik Rick C. Hodgin napisał:
> > Apologize for what, you bully?
> 
> for sharing stupidity stupid idiot

Technically I shared intelligence in that I realized through self-
thought what I didn't realize previously due to ignorance (not stupidity).

    ignorance = lack of knowledge, able to be overcome by
                learning, thinking, being taught new things
    stupidity = lack of intelligence, unable to be overcome

Vitriol hatred for others can also be overcome ... by love ... and
that love comes from Jesus Christ.

-- 
Rick C. Hodgin

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#144297

W dniu niedziela, 2 czerwca 2019 15:43:10 UTC+2 użytkownik Rick C. Hodgin napisał:
> On Sunday, June 2, 2019 at 9:24:58 AM UTC-4, fir wrote:
> > W dniu niedziela, 2 czerwca 2019 15:08:29 UTC+2 użytkownik Rick C. Hodgin napisał:
> > > Apologize for what, you bully?
> > 
> > for sharing stupidity stupid idiot
> 
> Technically I shared intelligence in that I realized through self-
> thought what I didn't realize previously due to ignorance (not stupidity).
> 
>     ignorance = lack of knowledge, able to be overcome by
>                 learning, thinking, being taught new things
>     stupidity = lack of intelligence, unable to be overcome
> 
and you think youre only ignorant but not stupid, stupid dik?

ignorance is ignorance, but if yopu want apologization in case you were right you should apologize in case you showed ignorant moron as always - dont you?

(i must worry you becouse youre not only ignorant but very stupid, and not only stupid but arrogant and vandalizing)

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#144314

On Sunday, June 2, 2019 at 10:06:11 AM UTC-4, fir wrote:
> W dniu niedziela, 2 czerwca 2019 15:43:10 UTC+2 użytkownik > ignorance is ignorance, but if yopu want apologization in case you were right you should apologize in case you showed ignorant moron as always - dont you?

No.  I was joking, fir.  I wouldn't expect any apologies if I were
right.  In addition, I said "metaphoric apology."

-- 
Rick C. Hodgin

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#144295

On Sunday, June 2, 2019 at 9:24:58 AM UTC-4, fir wrote:
> [snip]

There's a movie out that shows how God can turn around even
child-beating, wife-beating men, making them loving saints of
God.

    Movie:  I Can Only Imagine
    https://www.youtube.com/watch?v=KIkOAgxkAc8
    https://www.youtube.com/watch?v=OsMyv9Q4_OU

    Beaten daily by his father, Bart's pain culminated in the
    best selling Christian single of all time:

    https://www.youtube.com/watch?v=N_lrrq_opng

    Demonstrates what Jesus does to make us flawless:
    https://www.youtube.com/watch?v=wjLlLPZderk

-----
A man I knew who died in 2008 used to be the biggest drunk in
three counties.  One day he got saved and his whole life turned
around.  He was in his 60s when it happened.  Was named Larry King,
and called himself, "Larry King Alive."

It's never too late for anyone ... until they leave this world.
Then, their fate is sealed.

-- 
Rick C. Hodgin

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