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62 lines
2.1 KiB
62 lines
2.1 KiB
/*
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* Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* SPDX-FileCopyrightText: Copyright (c) 2014-2022 NVIDIA CORPORATION
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef RANDOM_GLSL
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#define RANDOM_GLSL 1
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precision highp float;
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// Generate a seed for the random generator.
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// Input - pixel.x, pixel.y, frame_nb
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// From https://github.com/Cyan4973/xxHash, https://www.shadertoy.com/view/XlGcRh
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uint xxhash32(uvec3 p)
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{
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const uvec4 primes = uvec4(2246822519U, 3266489917U, 668265263U, 374761393U);
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uint h32;
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h32 = p.z + primes.w + p.x * primes.y;
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h32 = primes.z * ((h32 << 17) | (h32 >> (32 - 17)));
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h32 += p.y * primes.y;
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h32 = primes.z * ((h32 << 17) | (h32 >> (32 - 17)));
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h32 = primes.x * (h32 ^ (h32 >> 15));
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h32 = primes.y * (h32 ^ (h32 >> 13));
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return h32 ^ (h32 >> 16);
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}
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//-----------------------------------------------------------------------
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// https://www.pcg-random.org/
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//-----------------------------------------------------------------------
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uint pcg(inout uint state)
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{
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uint prev = state * 747796405u + 2891336453u;
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uint word = ((prev >> ((prev >> 28u) + 4u)) ^ prev) * 277803737u;
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state = prev;
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return (word >> 22u) ^ word;
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}
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//-----------------------------------------------------------------------
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// Generate a random float in [0, 1) given the previous RNG state
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//-----------------------------------------------------------------------
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float rand(inout uint seed)
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{
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uint r = pcg(seed);
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return float(r) * (1.F / float(0xffffffffu));
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}
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#endif // RANDOM_GLSL
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