| /* |
| * Copyright (C) 2013 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef LE_FX_ENGINE_COMMON_CORE_MATH_H_ |
| #define LE_FX_ENGINE_COMMON_CORE_MATH_H_ |
| |
| #include <math.h> |
| #include <algorithm> |
| using ::std::min; |
| using ::std::max; |
| using ::std::fill; |
| using ::std::fill_n;using ::std::lower_bound; |
| #include <cmath> |
| #include <math.h> |
| //using ::std::fpclassify; |
| |
| #include "common/core/os.h" |
| #include "common/core/types.h" |
| |
| namespace le_fx { |
| namespace math { |
| |
| // A fast approximation to log2(.) |
| inline float fast_log2(float val) { |
| int* const exp_ptr = reinterpret_cast <int *> (&val); |
| int x = *exp_ptr; |
| const int log_2 = ((x >> 23) & 255) - 128; |
| x &= ~(255 << 23); |
| x += 127 << 23; |
| *exp_ptr = x; |
| val = ((-1.0f / 3) * val + 2) * val - 2.0f / 3; |
| return static_cast<float>(val + log_2); |
| } |
| |
| // A fast approximation to log(.) |
| inline float fast_log(float val) { |
| return fast_log2(val) * |
| 0.693147180559945286226763982995180413126945495605468750f; |
| } |
| |
| // An approximation of the exp(.) function using a 5-th order Taylor expansion. |
| // It's pretty accurate between +-0.1 and accurate to 10e-3 between +-1 |
| template <typename T> |
| inline T ExpApproximationViaTaylorExpansionOrder5(T x) { |
| const T x2 = x * x; |
| const T x3 = x2 * x; |
| const T x4 = x2 * x2; |
| const T x5 = x3 * x2; |
| return 1.0f + x + 0.5f * x2 + |
| 0.16666666666666665741480812812369549646973609924316406250f * x3 + |
| 0.0416666666666666643537020320309238741174340248107910156250f * x4 + |
| 0.008333333333333333217685101601546193705871701240539550781250f * x5; |
| } |
| |
| } // namespace math |
| } // namespace le_fx |
| |
| // Math functions missing in Android NDK: |
| #if defined(LE_FX_OS_ANDROID) |
| |
| namespace std { |
| |
| // |
| // Round to the nearest integer: We need this implementation |
| // since std::round is missing on android. |
| // |
| template <typename T> |
| inline T round(const T &x) { |
| return static_cast<T>(std::floor(static_cast<double>(x) + 0.5)); |
| } |
| |
| } // namespace std |
| |
| #endif // LE_FX_OS_ANDROID |
| |
| #endif // LE_FX_ENGINE_COMMON_CORE_MATH_H_ |