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deps/g3dlite/source/g3dmath.cpp

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+/**
+ @file g3dmath.cpp
+ 
+ @author Morgan McGuire, graphics3d.com
+  
+ @created 2001-06-02
+ @edited  2004-02-24
+ */
+
+#include "G3D/g3dmath.h"
+#include <cstdlib>
+#include <cstring>
+#include "G3D/BIN.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; 
+}
+
+/** 
+    This value should not be tested against directly, instead
+    G3D::isNan() and G3D::isFinite() will return reliable results. */
+double inf() {
+    return std::numeric_limits<double>::infinity();
+}
+
+// --fast-math breaks other methods of testing for NaN on g++ 4.x,
+// including isnan(x) and !(x == x)
+
+bool isNaN(float x) {
+    // Wipe out the sign bit
+    const uint32 y = *(uint32*)(&x) & BIN32(01111111,11111111,11111111,11111111);
+
+    // If the remaining number has all of the exponent bits set and atleast one
+    // fraction bit set, then it is NaN
+    return (y > 0x7F800000);
+}
+
+bool isNaN(double x) {
+    // Wipe out the sign bit
+    const uint64 y = *(uint64*)(&x) &
+        ((uint64(BIN32(01111111,11111111,11111111,11111111)) << 32) +
+         0xFFFFFFFF);
+
+    // If the remaining number has all of the exponent bits set and atleast one
+    // fraction bit set, then it is NaN
+    return (y > (uint64(BIN32(01111111,11110000,00000000,00000000)) << 32));
+}
+
+
+/** 
+    This value should not be tested against directly, instead
+    G3D::isNan() and G3D::isFinite() will return reliable results. */
+float finf() {
+    return std::numeric_limits<float>::infinity();
+}
+
+/** This value should not be tested against directly, instead
+    G3D::isNan() and G3D::isFinite() will return reliable results. */
+double nan() {
+    // double is a standard type and should have quiet NaN
+    return std::numeric_limits<double>::quiet_NaN();
+}
+
+float fnan() {
+    // double is a standard type and should have quiet NaN
+    return std::numeric_limits<float>::quiet_NaN();
+}
+
+
+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;
+    }
+}
+
+
+}