58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
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/*
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* Copyright (C) 2015 The Android Open Source Project
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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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#ifndef IBL_UTILITIES_H
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#define IBL_UTILITIES_H
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#include <math.h>
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#include <math/vec2.h>
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#include <math/vec3.h>
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namespace filament {
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namespace ibl {
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template<typename T>
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static inline constexpr T sq(T x) {
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return x * x;
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}
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template<typename T>
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static inline constexpr T log4(T x) {
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// log2(x)/log2(4)
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// log2(x)/2
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return std::log2(x) * T(0.5);
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}
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inline bool isPOT(size_t x) {
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return !(x & (x - 1));
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}
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inline filament::math::float2 hammersley(uint32_t i, float iN) {
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constexpr float tof = 0.5f / 0x80000000U;
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uint32_t bits = i;
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bits = (bits << 16u) | (bits >> 16u);
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bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
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bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
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bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
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bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
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return { i * iN, bits * tof };
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}
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} // namespace ibl
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} // namespace filament
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#endif /* IBL_UTILITIES_H */
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