RixRNGInline.h

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#ifndef RixRNGInline_h
#define RixRNGInline_h

// Convenience functions that can be used to generate sample values.
// This file is included by RixRNG.h.

#include "prmanapi.h"                   // for PRMAN_INLINE

namespace RixRNGUtils
{

// Compute a repeatable random float in [0,1) based on value and scramble
PRMAN_INLINE float
HashToRandom(const unsigned value, const unsigned scramble)
{
    // clang-format off
    unsigned result = value;
    result ^= scramble;
    result ^= result >> 17;
    result ^= result >> 10;  result *= 0xb36534e5;
    result ^= result >> 12;
    result ^= result >> 21;  result *= 0x93fc4795;
    result ^= 0xdf6e307f;
    result ^= result >> 17;  result *= 1 | scramble >> 18;
    return static_cast<float>(result) / 4298115584.0f;
    // clang-format on
}

PRMAN_INLINE unsigned
shufflePattern(
    const unsigned pattern,
    const unsigned scramble1 = 0xb2182ef5,
    const unsigned scramble2 = 0x1e1897a7)
{
    unsigned npattern = pattern * ((scramble1 << 1) | 1);
    // All odds are coprime with 2^16.
    npattern += scramble2;
    return npattern;
}

} // namespace RixRNGUtils

#endif