CmRandom.h

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// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.  
 
#ifndef CM_RANDOM_H
#define CM_RANDOM_H
 
#include "common/PxPhysXCommonConfig.h"
#define TEST_MAX_RAND 0xffff
 
namespace physx
{
namespace Cm
{
    class BasicRandom
    {
    public:
        BasicRandom(PxU32 seed = 0) : mRnd(seed) {}
        ~BasicRandom() {}
 
        PX_FORCE_INLINE void        setSeed(PxU32 seed) { mRnd = seed; }
        PX_FORCE_INLINE PxU32       getCurrentValue()   const { return mRnd; }
        PxU32       randomize() { mRnd = mRnd * 2147001325 + 715136305; return mRnd; }
 
        PX_FORCE_INLINE PxU32       rand() { return randomize() & 0xffff; }
        PX_FORCE_INLINE PxU32       rand32() { return randomize() & 0xffffffff; }
 
        PxF32       rand(PxF32 a, PxF32 b)
        {
            const PxF32 r = rand32() / (static_cast<PxF32>(0xffffffff));
            return r * (b - a) + a;
        }
 
        PxI32       rand(PxI32 a, PxI32 b)
        {
            return a + static_cast<PxI32>(rand32() % (b - a));
        }
 
        PxF32       randomFloat()
        {
            return rand() / (static_cast<PxF32>(0xffff)) - 0.5f;
        }
        PxF32       randomFloat32()
        {
            return rand32() / (static_cast<PxF32>(0xffffffff)) - 0.5f;
        }
 
        PxF32       randomFloat32(PxReal a, PxReal b) { return rand32() / PxF32(0xffffffff)*(b - a) + a; }
        void        unitRandomPt(physx::PxVec3& v)
        {
            v = unitRandomPt();
        }
 
        void        unitRandomQuat(physx::PxQuat& v)
        {
            v = unitRandomQuat();
        }
 
        PxVec3      unitRandomPt()
        {
            PxVec3 v;
            do
            {
                v.x = randomFloat();
                v.y = randomFloat();
                v.z = randomFloat();
            } while (v.normalize() < 1e-6f);
            return v;
        }
 
        PxQuat      unitRandomQuat()
        {
            PxQuat v;
            do
            {
                v.x = randomFloat();
                v.y = randomFloat();
                v.z = randomFloat();
                v.w = randomFloat();
            } while (v.normalize() < 1e-6f);
 
            return v;
        }
 
    private:
        PxU32       mRnd;
    };
 
    //--------------------------------------
    // Fast, very good random numbers
    //
    // Period = 2^249
    //
    // Kirkpatrick, S., and E. Stoll, 1981; A Very Fast Shift-Register
    //       Sequence Random Number Generator, Journal of Computational Physics,
    // V. 40.
    //
    // Maier, W.L., 1991; A Fast Pseudo Random Number Generator,
    // Dr. Dobb's Journal, May, pp. 152 - 157
 
    class RandomR250
    {
    public:
        RandomR250(PxI32 s)
        {
            setSeed(s);
        }
 
        void    setSeed(PxI32 s)
        {
            BasicRandom lcg(s);
            mIndex = 0;
 
            PxI32 j;
            for (j = 0; j < 250; j++)        // fill r250 buffer with bit values
                mBuffer[j] = lcg.randomize();
 
            for (j = 0; j < 250; j++)        // set some MSBs to 1
                if (lcg.randomize() > 0x40000000L)
                    mBuffer[j] |= 0x80000000L;
 
            PxU32 msb = 0x80000000;           // turn on diagonal bit
            PxU32 mask = 0xffffffff;           // turn off the leftmost bits
 
            for (j = 0; j < 32; j++)
            {
                const PxI32 k = 7 * j + 3;   // select a word to operate on
                mBuffer[k] &= mask;           // turn off bits left of the diagonal 
                mBuffer[k] |= msb;            // turn on the diagonal bit 
                mask >>= 1;
                msb >>= 1;
            }
        }
 
        PxU32 randI()
        {
            PxI32 j;
 
            // wrap pointer around 
            if (mIndex >= 147) j = mIndex - 147;
            else                 j = mIndex + 103;
 
            const PxU32 new_rand = mBuffer[mIndex] ^ mBuffer[j];
            mBuffer[mIndex] = new_rand;
 
            // increment pointer for next time
            if (mIndex >= 249) mIndex = 0;
            else                 mIndex++;
 
            return new_rand >> 1;
        }
 
        PxReal randUnit()
        {
            PxU32 mask = (1 << 23) - 1;
            return PxF32(randI()&(mask)) / PxF32(mask);
        }
 
        PxReal rand(PxReal lower, PxReal upper)
        {
            return lower + randUnit() * (upper - lower);
        }
 
    private:
        PxU32   mBuffer[250];
        PxI32   mIndex;
    };
 
    static RandomR250 gRandomR250(0x95d6739b);
 
    PX_FORCE_INLINE PxU32 Rand()
    {
        return gRandomR250.randI() & TEST_MAX_RAND;
    }
 
    PX_FORCE_INLINE PxF32 Rand(PxF32 a, PxF32 b)
    {
        const PxF32 r = static_cast<PxF32>(Rand()) / (static_cast<PxF32>(TEST_MAX_RAND));
        return r * (b - a) + a;
    }
    PX_FORCE_INLINE PxF32 RandLegacy(PxF32 a, PxF32 b)
    {
        const PxF32 r = static_cast<PxF32>(Rand()) / (static_cast<PxF32>(0x7fff) + 1.0f);
        return r * (b - a) + a;
    }
    //returns numbers from [a, b-1] 
    PX_FORCE_INLINE PxI32 Rand(PxI32 a, PxI32 b)
    {
        return a + static_cast<PxI32>(Rand() % (b - a));
    }
 
    PX_FORCE_INLINE void SetSeed(PxU32 seed)
    {
        gRandomR250.setSeed(seed);
    }
    
}
}
#endif