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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
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