99 lines
2.8 KiB
C++
99 lines
2.8 KiB
C++
/*
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* Copyright (C) 2014 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 MATHUTILS_H
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#define MATHUTILS_H
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#include <algorithm>
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#include <math.h>
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namespace android {
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namespace uirenderer {
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#define NON_ZERO_EPSILON (0.001f)
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#define ALPHA_EPSILON (0.001f)
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class MathUtils {
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public:
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/**
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* Check for floats that are close enough to zero.
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*/
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inline static bool isZero(float value) {
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return (value >= -NON_ZERO_EPSILON) && (value <= NON_ZERO_EPSILON);
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}
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inline static bool isPositive(float value) {
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return value >= NON_ZERO_EPSILON;
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}
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/**
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* Clamps alpha value, and snaps when very near 0 or 1
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*/
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inline static float clampAlpha(float alpha) {
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if (alpha <= ALPHA_EPSILON) {
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return 0;
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} else if (alpha >= (1 - ALPHA_EPSILON)) {
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return 1;
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} else {
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return alpha;
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}
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}
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/*
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* Clamps positive tessellation scale values
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*/
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inline static float clampTessellationScale(float scale) {
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const float MIN_SCALE = 0.0001;
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const float MAX_SCALE = 1e10;
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if (scale < MIN_SCALE) {
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return MIN_SCALE;
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} else if (scale > MAX_SCALE) {
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return MAX_SCALE;
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}
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return scale;
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}
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/**
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* Returns the number of points (beyond two, the start and end) needed to form a polygonal
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* approximation of an arc, with a given threshold value.
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*/
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inline static int divisionsNeededToApproximateArc(float radius,
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float angleInRads, float threshold) {
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const float errConst = (-threshold / radius + 1);
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const float targetCosVal = 2 * errConst * errConst - 1;
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// needed divisions are rounded up from approximation
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return (int)(ceilf(angleInRads / acos(targetCosVal)/2)) * 2;
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}
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inline static bool areEqual(float valueA, float valueB) {
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return isZero(valueA - valueB);
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}
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template<typename T>
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static inline T clamp(T a, T minValue, T maxValue) {
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return std::min(std::max(a, minValue), maxValue);
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}
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inline static float lerp(float v1, float v2, float t) {
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return v1 + ((v2 - v1) * t);
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}
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}; // class MathUtils
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} /* namespace uirenderer */
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} /* namespace android */
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#endif /* MATHUTILS_H */
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