71 lines
1.3 KiB
C++
71 lines
1.3 KiB
C++
/**
|
|
@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;
|
|
}
|
|
}
|
|
|
|
|
|
}
|