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