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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
#include "util/types.h"
CCL_NAMESPACE_BEGIN
/*
* Performs base-2 Owen scrambling on a reversed-bit integer.
*
* This is equivalent to the Laine-Karras permutation, but much higher
* quality. See https://psychopath.io/post/2021_01_30_building_a_better_lk_hash
*/
ccl_device_inline uint reversed_bit_owen(uint n, uint seed)
{
n ^= n * 0x3d20adea;
n += seed;
n *= (seed >> 16) | 1;
n ^= n * 0x05526c56;
n ^= n * 0x53a22864;
return n;
}
/*
* Performs base-2 Owen scrambling on a reversed-bit integer.
*
* This is here for backwards-compatibility, and can be replaced
* with reversed_bit_owen() above at some point.
* See https://developer.blender.org/D15679#426304
*/
ccl_device_inline uint laine_karras_permutation(uint x, uint seed)
{
x += seed;
x ^= (x * 0x6c50b47cu);
x ^= x * 0xb82f1e52u;
x ^= x * 0xc7afe638u;
x ^= x * 0x8d22f6e6u;
return x;
}
CCL_NAMESPACE_END
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