XCEngine/engine/third_party/physx/source/common/src/CmRandom.h

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#ifndef CM_RANDOM_H
#define CM_RANDOM_H

#include "foundation/PxQuat.h"
#include "foundation/PxVec3.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