# Difference between revisions of "Random Gaussian Number Generator"

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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)));
}```