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Added Fisher-Yates shuffle.

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This commit is contained in:
Branimir Karadžić
2016-11-20 13:41:16 -08:00
parent 4e277b4b25
commit b920d6675a
1 changed files with 22 additions and 8 deletions
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30
include/bx/rng.h
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@@ -8,6 +8,7 @@
#include "bx.h"
#include "fpumath.h"
#include "uint32_t.h"
namespace bx
{
@@ -94,23 +95,23 @@ namespace bx
};
/// Returns random number between 0.0f and 1.0f.
template <typename Ty>
inline float frnd(Ty* _rng)
template <typename Rng>
inline float frnd(Rng* _rng)
{
uint32_t rnd = _rng->gen() & UINT16_MAX;
return float(rnd) * 1.0f/float(UINT16_MAX);
}
/// Returns random number between -1.0f and 1.0f.
template <typename Ty>
inline float frndh(Ty* _rng)
template <typename Rng>
inline float frndh(Rng* _rng)
{
return 2.0f * bx::frnd(_rng) - 1.0f;
}
/// Generate random point on unit sphere.
template <typename Ty>
static inline void randUnitSphere(float _result[3], Ty* _rng)
template <typename Rng>
inline void randUnitSphere(float _result[3], Rng* _rng)
{
float rand0 = frnd(_rng) * 2.0f - 1.0f;
float rand1 = frnd(_rng) * pi * 2.0f;
@@ -123,7 +124,7 @@ namespace bx
/// Generate random point on unit hemisphere.
template <typename Ty>
static inline void randUnitHemisphere(float _result[3], Ty* _rng, const float _normal[3])
inline void randUnitHemisphere(float _result[3], Ty* _rng, const float _normal[3])
{
float dir[3];
randUnitSphere(dir, _rng);
@@ -148,7 +149,7 @@ namespace bx
/// Sampling with Hammersley and Halton Points
/// http://www.cse.cuhk.edu.hk/~ttwong/papers/udpoint/udpoints.html
///
static inline void generateSphereHammersley(void* _data, uint32_t _stride, uint32_t _num, float _scale = 1.0f)
inline void generateSphereHammersley(void* _data, uint32_t _stride, uint32_t _num, float _scale = 1.0f)
{
uint8_t* data = (uint8_t*)_data;
@@ -177,6 +178,19 @@ namespace bx
}
}
/// Fisher-Yates shuffle.
template<typename Rng, typename Ty>
inline void shuffle(Rng* _rng, Ty* _array, uint32_t _num)
{
BX_CHECK(_num != 0, "Number of elements can't be 0!");
for (uint32_t ii = 0, num = _num-1; ii < num; ++ii)
{
uint32_t jj = ii + 1 + _rng->gen() % (num - ii);
bx::xchg(_array[ii], _array[jj]);
}
}
} // namespace bx
#endif // BX_RNG_H_HEADER_GUARD