fir <profesor.fir@gmail.com> wrote:
> i need to set 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 density near it
> and less desity with bigger radius until some radius when it is zero
>
> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);
>
> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?

Haven't read the followups. You mean something like...
https://www.deviantart.com/eigenheit22/art/Starfield-v1-860092004
....without the animation? That's done in x,y (and z). And you can then
just calculate r=sqrt(x*x+y*y) and discard the ones you don't like.
--
John Forkosh ( mailto: j@f.com where j=john and f=forkosh )

sobota, 5 sierpnia 2023 o 12:57:46 UTC+2 John Forkosh napisał(a):
> fir <profes...@gmail.com> wrote:
> > i need to set 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 density near it
> > and less desity with bigger radius until some radius when it is zero
> >
> > something like
> >
> > SetRandomPointSphericalSymetricAndFadingWithDistance(
> > float x, float y, float r1, float r2);
> >
> > this r1 is radius of circle below which density is max and r2 is radius
> > where above density is zero - in beetweem r1 and r2 density should
> > be from max (at r1) to zero at r2
> >
> > how to do that?
> Haven't read the followups. You mean something like...
> https://www.deviantart.com/eigenheit22/art/Starfield-v1-860092004
> ...without the animation? That's done in x,y (and z). And you can then
> just calculate r=sqrt(x*x+y*y) and discard the ones you don't like.

possibly - now i think you just can imagine field of discarding (from 0.0 to 1.0 chance of discarding in given point) then just calculate chnce of discarding in that point according to a field and use it

thsi is a bit wastefull to count something than discard it but probably could be enough ok

On 7/18/2023 11:38 PM, fir wrote:
> 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
>
> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);
>
> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?

Fwiw, check out this older simulation I made around 9 years ago:

https://youtu.be/-EaHLaZbMFs

It tries to diffuse itself...

fir <profesor.fir@gmail.com> wrote:
> John Forkosh wrote(a):
>> fir <profes...@gmail.com> wrote:
>> > i need to set 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 density near it
>> > and less desity with bigger radius until some radius when it is zero
>> >
>> > something like
>> > SetRandomPointSphericalSymetricAndFadingWithDistance(
>> > float x, float y, float r1, float r2);
>> > this r1 is radius of circle below which density is max and r2 is radius
>> > where above density is zero - in beetweem r1 and r2 density should
>> > be from max (at r1) to zero at r2
>> > how to do that?
>>
>> Haven't read the followups. You mean something like...
>> https://www.deviantart.com/eigenheit22/art/Starfield-v1-860092004
>> ...without the animation? That's done in x,y (and z). And you can then
>> just calculate r=sqrt(x*x+y*y) and discard the ones you don't like.
>
> possibly - now i think you just can imagine field of discarding
> (from 0.0 to 1.0 chance of discarding in given point) then just
> calculate chnce of discarding in that point according to a field
> and use it
>
> this is a bit wasteful to count something than discard it but
> probably could be enough ok

You said 100-200 asteroids, so "wasteful" is hardly a concern.
But if you're concerned anyway, suppose you wanted asteroids
at radius r1 <= r <= r2 (you wanted "max density" at r<=r1,
whereas this will give 0 at r<r1 and r>r2; your exercise is to
figure out the necessary modification). So go back to r,theta
polar coords and just do something along the following lines...
#include <stdlib.h>
#include <math.h>
void SetRandomPoint( double r1, double r2, double *x, double *y ) {
double r = r1 + (r2-r1)*drand48(), /* random r1<=r<r2 */
theta = 2.0*3.14159*drand48(); /* random 0<=theta<2pi */
*x = r*cos(theta); *y = r*sin(theta); /* return random x,y coords */
return; }
And the density will naturally decrease with increasing r.
No work required.
--
John Forkosh ( mailto: j@f.com where j=john and f=forkosh )

poniedziałek, 7 sierpnia 2023 o 15:13:37 UTC+2 John Forkosh napisał(a):
> fir <profes...@gmail.com> wrote:
> > John Forkosh wrote(a):
> >> fir <profes...@gmail.com> wrote:
> >> > i need to set 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 density near it
> >> > and less desity with bigger radius until some radius when it is zero
> >> >
> >> > something like
> >> > SetRandomPointSphericalSymetricAndFadingWithDistance(
> >> > float x, float y, float r1, float r2);
> >> > this r1 is radius of circle below which density is max and r2 is radius
> >> > where above density is zero - in beetweem r1 and r2 density should
> >> > be from max (at r1) to zero at r2
> >> > how to do that?
> >>
> >> Haven't read the followups. You mean something like...
> >> https://www.deviantart.com/eigenheit22/art/Starfield-v1-860092004
> >> ...without the animation? That's done in x,y (and z). And you can then
> >> just calculate r=sqrt(x*x+y*y) and discard the ones you don't like.
> >
> > possibly - now i think you just can imagine field of discarding
> > (from 0.0 to 1.0 chance of discarding in given point) then just
> > calculate chnce of discarding in that point according to a field
> > and use it
> >
> > this is a bit wasteful to count something than discard it but
> > probably could be enough ok
> You said 100-200 asteroids, so "wasteful" is hardly a concern.
> But if you're concerned anyway, suppose you wanted asteroids
> at radius r1 <= r <= r2 (you wanted "max density" at r<=r1,
> whereas this will give 0 at r<r1 and r>r2; your exercise is to
> figure out the necessary modification). So go back to r,theta
> polar coords and just do something along the following lines...
> #include <stdlib.h>
> #include <math.h>
> void SetRandomPoint( double r1, double r2, double *x, double *y ) {
> double r = r1 + (r2-r1)*drand48(), /* random r1<=r<r2 */
> theta = 2.0*3.14159*drand48(); /* random 0<=theta<2pi */
> *x = r*cos(theta); *y = r*sin(theta); /* return random x,y coords */
> return; }
> And the density will naturally decrease with increasing r.
> No work required.

i wanted max constand density say in radius 100 then linerally decaying say
in radius from 300

it seems the rand only givesflat density, then probably proper way fould be to tranmsform/project this square cordinates into other shape as density is proportional to 'surface'if some transforms the surface stretching it or densing by some x,y -> x', y' then it will have les random density

but i dont remember how to do transformations ([probably they are normal functions of x,y into new x,y so some could be found) but there is also thsi way with making fields of percentage of discarding

this function is handy to me but its also not any way critical i need it jsu to set things in agme liak asteroid fields, space flowers or something liek that (but dont hope it would be look god i only write games wth symbolic graphics, something like kinda roguelikes)

poniedziałek, 7 sierpnia 2023 o 15:26:44 UTC+2 fir napisał(a):
> poniedziałek, 7 sierpnia 2023 o 15:13:37 UTC+2 John Forkosh napisał(a):
> > fir <profes...@gmail.com> wrote:
> > > John Forkosh wrote(a):
> > >> fir <profes...@gmail.com> wrote:
> > >> > i need to set 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 density near it
> > >> > and less desity with bigger radius until some radius when it is zero
> > >> >
> > >> > something like
> > >> > SetRandomPointSphericalSymetricAndFadingWithDistance(
> > >> > float x, float y, float r1, float r2);
> > >> > this r1 is radius of circle below which density is max and r2 is radius
> > >> > where above density is zero - in beetweem r1 and r2 density should
> > >> > be from max (at r1) to zero at r2
> > >> > how to do that?
> > >>
> > >> Haven't read the followups. You mean something like...
> > >> https://www.deviantart.com/eigenheit22/art/Starfield-v1-860092004
> > >> ...without the animation? That's done in x,y (and z). And you can then
> > >> just calculate r=sqrt(x*x+y*y) and discard the ones you don't like..
> > >
> > > possibly - now i think you just can imagine field of discarding
> > > (from 0.0 to 1.0 chance of discarding in given point) then just
> > > calculate chnce of discarding in that point according to a field
> > > and use it
> > >
> > > this is a bit wasteful to count something than discard it but
> > > probably could be enough ok
> > You said 100-200 asteroids, so "wasteful" is hardly a concern.
> > But if you're concerned anyway, suppose you wanted asteroids
> > at radius r1 <= r <= r2 (you wanted "max density" at r<=r1,
> > whereas this will give 0 at r<r1 and r>r2; your exercise is to
> > figure out the necessary modification). So go back to r,theta
> > polar coords and just do something along the following lines...
> > #include <stdlib.h>
> > #include <math.h>
> > void SetRandomPoint( double r1, double r2, double *x, double *y ) {
> > double r = r1 + (r2-r1)*drand48(), /* random r1<=r<r2 */
> > theta = 2.0*3.14159*drand48(); /* random 0<=theta<2pi */
> > *x = r*cos(theta); *y = r*sin(theta); /* return random x,y coords */
> > return; }
> > And the density will naturally decrease with increasing r.
> > No work required.
> i wanted max constand density say in radius 100 then linerally decaying say
> in radius from 300
>
> it seems the rand only givesflat density, then probably proper way fould be to tranmsform/project this square cordinates into other shape as density is proportional to 'surface'if some transforms the surface stretching it or densing by some x,y -> x', y' then it will have les random density
>

this waht you say is in fact such trabsformation x,x->x',y' buts its kinda wrong
becouse near radius zero it has no limited densityand in radius 0.1 you got 10 percent
of all asteroids which simply might be to high..so i gusee there is soem another transformation which coudl be found better..though still its probably a bit harder to write it nly by transformation without discarding

> but i dont remember how to do transformations ([probably they are normal functions of x,y into new x,y so some could be found) but there is also thsi way with making fields of percentage of discarding
>
> this function is handy to me but its also not any way critical i need it jsu to set things in agme liak asteroid fields, space flowers or something liek that (but dont hope it would be look god i only write games wth symbolic graphics, something like kinda roguelikes)

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

something like

SetRandomPointSphericalSymetricAndFadingWithDistance(
float x, float y, float r1, float r2);

this r1 is radius of circle below which density is max and r2 is radius
where above density is zero - in beetweem r1 and r2 density should
be from max (at r1) to zero at r2

how to do that?

On Wednesday, 19 July 2023 at 07:38:10 UTC+1, fir wrote:
> 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
>
> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);
>
> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?
>
Th easy way to do it is to create three random values on -radius to radius, then calculate
the length with sqrt(x*x + y*y +z*z). If the length is greater thanthe radius, reject and
try again.
Matematicians don't like this because as you scale up to higher dimensions it becomes
less and less efficient.

If yiu want to solve the problem generally, try this link.
https://deepblue.lib.umich.edu/handle/2027.42/35534

On Wednesday, 19 July 2023 at 07:38:10 UTC+1, fir wrote:
> 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
>
> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);
>
> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?
>
Sorry, I misread your post.

You can probaly get away with caluclating the angle using a uniform random number,
and devising some non-uniform random number for the distance. A curve with a box
out to r1 and a triangle out to r2 wil probably suffice.
You need to integrate the curve, which sounds scary, but all it means is that you need
the area of the box (width time height) and the are of the triangle (hlaf width times
height). That tells you if the unform random number is inthe box or the triangle. If
it's inthe box, it;s a simple division to get how far along the box it is on the x co-ordinate.
If it's in the triangle, it's a bit more involved. You need solve the equation 0.5( 1-x)^2 = p,
where p is your uniform random number, rescaled to lop off the proportion of the box.

środa, 19 lipca 2023 o 10:49:09 UTC+2 Malcolm McLean napisał(a):
> On Wednesday, 19 July 2023 at 07:38:10 UTC+1, fir wrote:
> > 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
> >
> > something like
> >
> > SetRandomPointSphericalSymetricAndFadingWithDistance(
> > float x, float y, float r1, float r2);
> >
> > this r1 is radius of circle below which density is max and r2 is radius
> > where above density is zero - in beetweem r1 and r2 density should
> > be from max (at r1) to zero at r2
> >
> > how to do that?
> >
> Th easy way to do it is to create three random values on -radius to radius, then calculate
> the length with sqrt(x*x + y*y +z*z). If the length is greater thanthe radius, reject and
> try again.
> Matematicians don't like this because as you scale up to higher dimensions it becomes
> less and less efficient.
>

its okay though as i said i sont need only to have random in circle but gave linearrly more near centre and linearly less far from centre until some radius when i have none

but possibly i can made it with a percent of rejection... i mean count percent of rejection

float percent_of_rejection = (r-r1)(r2-r1); then use it to reject

int do_reject = rand2(0,100)<percent_of_rejection *100;

if(!do_reject)
{ //add
}

something like taht probably its ok, i dont need top efficiency or acurracy its for initialisation of goroups of asteroid or other things like that in 2d space

On 2023-07-19, fir <profesor.fir@gmail.com> wrote:
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2

Kinda like your hydrocephalic melon?

fir <profesor.fir@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.

> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);

This suggests that I've not understood your opening paragraph, but I
offer the solution in case someone else might be interested.

> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?

--
Ben.

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

generally i need whole pack of functions to set things arndomly but not just in rectangle whuich
will be given by applaying rand to x and y
this spherical group with decaying density with radius is one of that

> > something like
> >
> > SetRandomPointSphericalSymetricAndFadingWithDistance(
> > float x, float y, float r1, float r2);
> This suggests that I've not understood your opening paragraph, but I
> offer the solution in case someone else might be interested.
> > this r1 is radius of circle below which density is max and r2 is radius
> > where above density is zero - in beetweem r1 and r2 density should
> > be from max (at r1) to zero at r2
> >
> > how to do that?
> --
> Ben.

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.

czwartek, 20 lipca 2023 o 21:43:02 UTC+2 Ben Bacarisse napisał(a):
> fir <profes...@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.
>

no i just need to add rangom grou[p which is randomly spgerical amd has more density near centre and which get downs to zero at some radius R2
the centre of it (with some radius R) should have some flat density ...iys not just much important what but flad

say i need to put 200 asteroids around some point - in rhe radius say 500 meters they should have 100% density between radius 500 to 1000 metars the density should drop to 0%

On 7/18/2023 11:38 PM, fir wrote:
> 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
>
> something like
>
> SetRandomPointSphericalSymetricAndFadingWithDistance(
> float x, float y, float r1, float r2);
>
> this r1 is radius of circle below which density is max and r2 is radius
> where above density is zero - in beetweem r1 and r2 density should
> be from max (at r1) to zero at r2
>
> how to do that?

Diffuse the points around the central point. This is an example however
it has a bias in the corners of the rotated unit square:

http://fractallife247.com/fdla/

Click around.

On 7/20/2023 9:31 AM, fir wrote:
> 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
>
> generally i need whole pack of functions to set things arndomly but not just in rectangle whuich
> will be given by applaying rand to x and y
> this spherical group with decaying density with radius is one of that
>
>>> something like
>>>
>>> SetRandomPointSphericalSymetricAndFadingWithDistance(
>>> float x, float y, float r1, float r2);
>> This suggests that I've not understood your opening paragraph, but I
>> offer the solution in case someone else might be interested.
>>> this r1 is radius of circle below which density is max and r2 is radius
>>> where above density is zero - in beetweem r1 and r2 density should
>>> be from max (at r1) to zero at r2
>>>
>>> how to do that?

Random angles and random radii that are locked in the unit circle?
Should be good enough?

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

> czwartek, 20 lipca 2023 o 21:43:02 UTC+2 Ben Bacarisse napisał(a):
>> fir <profes...@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.
>
> no i just need to add rangom grou[p which is randomly spgerical amd
> has more density near centre and which get downs to zero at some
> radius R2 the centre of it (with some radius R) should have some flat
> density ...iys not just much important what but flad

I wish you well. If you want to ask in a group where English is widely
used, can you find someone to review your posts? I have no idea what
you are asking, but please don't spend any time explaining it -- I don't
need to know.

--
Ben.

czwartek, 20 lipca 2023 o 21:57:33 UTC+2 Chris M. Thomasson napisał(a):
> On 7/20/2023 9:31 AM, fir wrote:
> >>> how to do that?
> Random angles and random radii that are locked in the unit circle?
> Should be good enough?

i dont know maybe randomize in circle of R2 then in some steps randomize in smaller circle until i reach R1 ?

there should be some easy methods i guess..hovevver im not sur if geting random in polar coordinates gives really random in 2d space...maybe its natorally more density near centre then?

czwartek, 20 lipca 2023 o 21:43:02 UTC+2 Ben Bacarisse napisał(a):
> fir <profes...@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.
>

you mean hust getting random radius + random angle tend to do more density for smal radius - you may be right... i didnt get it in fiorst moment...yjere may be some problem though that it provides to high density near centra and here i need tio have flat density not linearly rise till zero

On 20/07/2023 21:56, fir wrote:
> czwartek, 20 lipca 2023 o 21:43:02 UTC+2 Ben Bacarisse napisał(a):
>> fir <profes...@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.
>>
>
> no i just need to add rangom grou[p which is randomly spgerical amd has more density near centre and which get downs to zero at some radius R2
> the centre of it (with some radius R) should have some flat density ...iys not just much important what but flad
>
> say i need to put 200 asteroids around some point - in rhe radius say 500 meters they should have 100% density between radius 500 to 1000 metars the density should drop to 0%

const double outer_radius = 1000;
const double inner_radius = 1000;

const double pi = 4 * atan(1);

double distance_to_asteroid = drand48() * (outer_radius - inner_radius)
+ inner_radius;
double angle_in_radians = 2 * pi * drand48();

Does that help?

If not, I'm with Ben - if you want help, you'll have to explain the task
better, and explain why this won't work.

piątek, 21 lipca 2023 o 09:15:59 UTC+2 David Brown napisał(a):
> On 20/07/2023 21:56, fir wrote:
> > czwartek, 20 lipca 2023 o 21:43:02 UTC+2 Ben Bacarisse napisał(a):
> >> fir <profes...@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.
> >>
> >
> > no i just need to add rangom grou[p which is randomly spgerical amd has more density near centre and which get downs to zero at some radius R2
> > the centre of it (with some radius R) should have some flat density ...iys not just much important what but flad
> >
> > say i need to put 200 asteroids around some point - in rhe radius say 500 meters they should have 100% density between radius 500 to 1000 metars the density should drop to 0%
> const double outer_radius = 1000;
> const double inner_radius = 1000;
>
> const double pi = 4 * atan(1);
>
> double distance_to_asteroid = drand48() * (outer_radius - inner_radius)
> + inner_radius;
> double angle_in_radians = 2 * pi * drand48();
>
> Does that help?
>
> If not, I'm with Ben - if you want help, you'll have to explain the task
> better, and explain why this won't work.

help is wrong word here i state topic, as opportunity to say something, dont need help
in a strict sense of this world - one need help if has a serious problem he cant overcome and
that kind of things is not like that

btw better write int rand2(int min, int max) function as i do, using this naked form is generally stupid imo

no i dont want to put an asteroid in 'cylinder' from radius r1 to r2
i want to set most of them in circle r1 and rest in cylinder from r1 to r2 such way it would look naturally such as a n group of astronomical things or pieces of things when you shatter them on the floor - most density in the centre till r1 less near r2 and none outside r2

this one with just
for(int i=0; i<200;i++) { r = rand2(r1,r2); a = rand2(1,360); }

i yet not tested but i got a feeling it isnt enough good (will test in evening)
probably something like said

for(float r=r2; i<r1; r-=(r2-r1)/200.)
{
PutRandomInCurcle(z,y,r);
}

could be somewhat better (It puts random in circle which is shrinking thus the edges will have less then centre

On Friday, July 21, 2023 at 8:55:36 AM UTC-4, fir wrote:
[]
> no i dont want to put an asteroid in 'cylinder' from radius r1 to r2
> i want to set most of them in circle r1 and rest in cylinder from r1 to r2
> such way it would look naturally such as a n group of astronomical things
> or pieces of things when you shatter them on the floor - most density in
> the centre till r1 less near r2 and none outside r2
>
I suggest you define your expected distribution first.
You might begin by defining the distribution you really want.
case 1: Is it constant density from 0 to r1 and then linear decline of density from r` to r2?
case 2: is is a natural distribution of "astronomical things"?
(clearly not like case 1, consider the solar system, including the asteroid belt)
case 3: is it a random scattering as "when you shatter them on the floor"
(clearly not like case 1 or 2. This is a gaussian distribution.)
case 4: SOMETHING ELSE???

State your desire clearly and we may be able to help you. Without a clear goal,
you'll be debugging potential solutions forever.

Ed

sobota, 22 lipca 2023 o 21:24:23 UTC+2 Ed Prochak napisał(a):
> On Friday, July 21, 2023 at 8:55:36 AM UTC-4, fir wrote:
> []
> > no i dont want to put an asteroid in 'cylinder' from radius r1 to r2
> > i want to set most of them in circle r1 and rest in cylinder from r1 to r2
> > such way it would look naturally such as a n group of astronomical things
> > or pieces of things when you shatter them on the floor - most density in
> > the centre till r1 less near r2 and none outside r2
> >
> I suggest you define your expected distribution first.
> You might begin by defining the distribution you really want.
> case 1: Is it constant density from 0 to r1 and then linear decline of density from r` to r2?
> case 2: is is a natural distribution of "astronomical things"?
> (clearly not like case 1, consider the solar system, including the asteroid belt)
> case 3: is it a random scattering as "when you shatter them on the floor"
> (clearly not like case 1 or 2. This is a gaussian distribution.)
> case 4: SOMETHING ELSE???
>
> State your desire clearly and we may be able to help you. Without a clear goal,
> you'll be debugging potential solutions forever.
>
> Ed

i dont care to much exactly i need to set a pack of 200 asteroids around some point to look good (but this should be not to much density in centre, ilke 10 asteroid cover the same piece of screen, thety may cover partially, but not like stack in 10 in one place)...also i want to use this function to set other things like in random group (but not like brush in pain, its more like more density in centre (where centre is not point but circle) and gradually less from r1 to r2

i think its not hard to understand what i want

in fact i may need more on this like some function tos et random 'stars' points in color/colors to make something that would look like nice looking photographs of galexies, making nice looking random groups (for a use of 2d cosmic space game)

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

> sobota, 22 lipca 2023 o 21:24:23 UTC+2 Ed Prochak napisał(a):
>> On Friday, July 21, 2023 at 8:55:36 AM UTC-4, fir wrote:
>> []
>> > no i dont want to put an asteroid in 'cylinder' from radius r1 to r2
>> > i want to set most of them in circle r1 and rest in cylinder from r1 to r2
>> > such way it would look naturally such as a n group of astronomical things
>> > or pieces of things when you shatter them on the floor - most density in
>> > the centre till r1 less near r2 and none outside r2
>> >
>> I suggest you define your expected distribution first.
>> You might begin by defining the distribution you really want.
>> case 1: Is it constant density from 0 to r1 and then linear decline of density from r` to r2?
>> case 2: is is a natural distribution of "astronomical things"?
>> (clearly not like case 1, consider the solar system, including the asteroid belt)
>> case 3: is it a random scattering as "when you shatter them on the floor"
>> (clearly not like case 1 or 2. This is a gaussian distribution.)
>> case 4: SOMETHING ELSE???
>>
>> State your desire clearly and we may be able to help you. Without a clear goal,
>> you'll be debugging potential solutions forever.
>>
>> Ed
>
> i dont care to much exactly i need to set a pack of 200 asteroids
> around some point to look good (but this should be not to much density
> in centre, ilke 10 asteroid cover the same piece of screen, thety may
> cover partially, but not like stack in 10 in one place)...also i want
> to use this function to set other things like in random group (but not
> like brush in pain, its more like more density in centre (where centre
> is not point but circle) and gradually less from r1 to r2

A bit like these:

http://bsb.me.uk/tmp/r1.png
http://bsb.me.uk/tmp/r2.png

> i think its not hard to understand what i want

It's hard to understand what you write. I am sure what you want is
quite simple. This is not about C so I'm going to crosspost to
comp.programming and set followups. I won't post about it here again.

--
Ben.