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+/**
+ @file PrecomputedRandom.h
+ 
+ @maintainer Morgan McGuire, http://graphics.cs.williams.edu
+ 
+ @created 2009-03-31
+ @edited  2009-03-31
+
+ Copyright 2000-2009, Morgan McGuire.
+ All rights reserved.
+ */
+#ifndef G3D_PrecomputedRandom_h
+#define G3D_PrecomputedRandom_h
+
+#include "G3D/platform.h"
+#include "G3D/Random.h"
+
+namespace G3D {
+
+/** Fast random numbers using a precomputed data table. 
+
+    e.g., generates cosHemi about 13x faster than Random.
+    This is useful for quickly generating seeded random 
+    numbers for reproducibility.  G3D::Random takes a long
+    time to seed; this is instantaneous (providing the 
+    precomputed data is already available.)
+
+    Not threadsafe.*/
+class PrecomputedRandom : public Random {
+public:
+    /** Put the cosHemi and the uniform together so that when
+        alternating between them we stay in cache. This is also packed
+        into a good size for SIMD and GPU operations.*/
+    class HemiUniformData {
+    public:
+        float   cosHemiX;
+        float   cosHemiY;
+        float   cosHemiZ;
+        float   uniform;
+    };
+
+    class SphereBitsData {
+    public:
+        float   sphereX;
+        float   sphereY;
+        float   sphereZ;
+        uint32  bits;
+    };
+
+protected:
+
+    /** Array of 2^n elements. */
+    const HemiUniformData*      m_hemiUniform;
+    const SphereBitsData*       m_sphereBits;
+
+    /** 2^n - 1; the AND mask for computing a fast modulo */
+    int                         m_modMask;
+
+    int                         m_index;
+
+    /** If true, free m_hemiUniform and m_sphereBits in destructor */
+    bool                        m_freeData;
+
+public:
+
+    /*
+      \param dataSize Must be a power of 2
+      \param data Will NOT be deleted by the destructor.
+     */
+    PrecomputedRandom(const HemiUniformData* data1, const SphereBitsData* data2, int dataSize, uint32 seed = 0xF018A4D2);
+
+    /**
+      \param dataSize Number of random numbers that can be requested before periodicity.  Must be a power of 2.
+      */
+    PrecomputedRandom(int dataSize, uint32 seed = 0xF018A4D2);
+
+    ~PrecomputedRandom();
+
+    /** Each bit is random.  Subclasses can choose to override just 
+       this method and the other methods will all work automatically. */
+    virtual uint32 bits();
+
+    // integer is inherited
+
+    /** Uniform random float on the range [min, max] */
+    virtual float uniform(float low, float high);
+
+    /** Uniform random float on the range [0, 1] */
+    virtual float uniform();
+
+    // gaussian is inherited
+
+    /** Returns 3D unit vectors distributed according to 
+        a cosine distribution about the z axis. */
+    virtual void cosHemi(float& x, float& y, float& z);
+
+    /** Returns 3D unit vectors distributed according to a cosine
+        power distribution (\f$ \mbox{cos}^k \theta \f$) about
+        the z-axis. */
+    virtual void cosPowHemi(const float k, float& x, float& y, float& z);
+
+    // hemi is inherited
+
+    /** Returns 3D unit vectors uniformly distributed on the sphere */
+    virtual void sphere(float& x, float& y, float& z);
+};
+
+}
+
+#endif