/**
 @file g3dmath.cpp
 
 @author Morgan McGuire, graphics3d.com
  
 @created 2001-06-02
 @edited  2004-02-24
 */

#include "G3D/g3dmath.h"
#include <stdlib.h>

namespace G3D {

float gaussRandom(float mean, float stdev) {

    // Using Box-Mueller method from http://www.taygeta.com/random/gaussian.html
    // Modified to specify standard deviation and mean of distribution
    float w, x1, x2;

    // Loop until w is less than 1 so that log(w) is negative
    do {
        x1 = uniformRandom(-1.0, 1.0);
        x2 = uniformRandom(-1.0, 1.0);

        w = float(square(x1) + square(x2));
    } while (w > 1.0f);

    // Transform to gassian distribution
    // Multiply by sigma (stdev ^ 2) and add mean.
    return x2 * (float)square(stdev) * sqrtf((-2.0f * logf(w) ) / w) + mean; 
}


int highestBit(uint32 x) {
    // Binary search.
    int base = 0;

	if (x & 0xffff0000)	{
		base = 16;
		x >>= 16;
	}
    if (x & 0x0000ff00) {
		base += 8;
		x >>= 8;
	}
    if (x & 0x000000f0) {
		base += 4;
		x >>= 4;
	}

	static const int lut[] = {-1,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3};
	return base + lut[x];
}


int iRandom(int low, int high) {
	int r = iFloor(low + (high - low + 1) * (double)rand() / RAND_MAX);

	// There is a *very small* chance of generating
	// a number larger than high.
	if (r > high) {
		return high;
	} else {
		return r;
	}
}


}