Random Gaussian Number Generator
Revision as of 07:43, 25 January 2015 by ObviousAltIsObvious Resident (talk | contribs) (<lsl> tag to <source>)
Port of the Random Gaussian algorithm found on http://www.taygeta.com/random/gaussian.html.
float randGauss(float mean, float stdev){
float x, y, r2;
do{//Generate a point in a unit circle that is not zero.
x = llFrand(2.) - 1;
y = llFrand(2.) - 1;
r2 = x * x + y * y;
} while (r2 > 1.0 || r2 == 0);
//Box-Muller transformation
return mean + x * stdev * llSqrt( -2 * llLog(r2) / r2);
}
vector randGaussPair(vector center, float stdev){//2D
//returns a random point on the x/y plain with a specified standard deviation from center.
float r2;
vector p;
do{//Generate a point in a unit circle that is not zero.
p = <llFrand(2.) - 1, llFrand(2.) - 1, 0>;
r2 = p * p;//dot product
} while (r2 > 1.0 || r2 == 0);
//Box-Muller transformation
return center + (p * (stdev * llSqrt( -2 * llLog(r2) / r2)));
}
Box-Muller Transformation
The Box-Muller transformation is used to adjust the magnitude of the vector, remapping it to a standard deviation.
3D
Is this correct? Or does Box-Muller need to be adjusted?
vector randGaussPoint(vector center, float stdev){//3D
//returns a random point with a specified standard deviation from center?
float r2;
vector p;
do{//Generate a point in a unit sphere that is not zero.
p = <llFrand(2.) - 1, llFrand(2.) - 1, llFrand(2.) - 1>;
r2 = p * p;//dot product
} while (r2 > 1.0 || r2 == 0);
//Box-Muller transformation
return center + (p * (stdev * llSqrt( -2 * llLog(r2) / r2)));
}