If the radius is a simple random number, then the point density varies with
the inverse square of the radius.  This code compensates for the variance:

#macro EvenSpherePoint(pos, rad, sd)
    #local irad = sqrt(min(rand(sd),0);
    #local theta = rand(sd)*2*pi;
    #local phi = (rand(sd)-0.5)*pi;
    #local dir = <cos(phi)*cos(theta), sin(phi), cos(phi)*sin(theta)>;
    #local pnt = pos+dir*irad*rad;
    pnt
#end

To use it--

#declare sdBall = seed(4852); // Sample number
#declare bPos = <0, 0, 0>;
#declare bSiz = 5;

sphere { bPos, bSiz
    pigment { rgbt 1 }
    hollow
    interior { /* your media */ }
}

#local i = 0;
#while (i<45)
    #local col = <rand(sdBall), rand(sdBall), rand(sdBall)>;
    #local pos = EvenSpherePoint(bPos, bSiz, sdBall);
    light_source { pos, rgb col }
    #local i = i + 1; // if using MegaPov v1.0 #set will work
#end

Now you avoid having to check for the sphere's boundary with each point.

"Warp" <war### [at] tagpovrayorg> wrote in message
news:3fa8cf58@news.povray.org...
> Kurts <kur### [at] yahoofr> wrote:
> > take a rayon
> > take a random number from 0 to 360
> > take an other random number from +90 to -90
> > then just convert polar coordonates from this 3 number to rectangular
<x,y,z>
>
> > pretty simply
>
>   You don't get an even distribution that way.
>
> -- 
> #macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb
M()}}
> N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
> N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  -
Warp -

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