1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef VECTOR2_H_ 6 #define VECTOR2_H_ 7 8 #include <stdlib.h> 9 #include <cmath> 10 #include <limits> 11 12 // A small class that encapsulates a 2D vector. Provides a few simple 13 // operations. 14 15 class Vector2 { 16 public: 17 Vector2() : x_(0.0), y_(0.0) {} 18 Vector2(double x, double y) : x_(x), y_(y) {} 19 ~Vector2() {} 20 21 // Create a new vector that represents a - b. 22 static Vector2 Difference(const Vector2& a, const Vector2& b) { 23 Vector2 diff(a.x() - b.x(), a.y() - b.y()); 24 return diff; 25 } 26 27 // The magnitude of this vector. 28 double Magnitude() const { 29 return sqrt(x_ * x_ + y_ * y_); 30 } 31 32 // Add |vec| to this vector. Works in-place. 33 void Add(const Vector2& vec) { 34 x_ += vec.x(); 35 y_ += vec.y(); 36 } 37 38 // Normalize this vector in-place. If the vector is degenerate (size 0) 39 // then do nothing. 40 void Normalize() { 41 double mag = Magnitude(); 42 if (fabs(mag) < std::numeric_limits<double>::epsilon()) 43 return; 44 Scale(1.0 / mag); 45 } 46 47 // Scale the vector in-place by |scale|. 48 void Scale(double scale) { 49 x_ *= scale; 50 y_ *= scale; 51 } 52 53 // Clamp a vector to a maximum magnitude. Works on the vector in-place. 54 // @param max_mag The maximum magnitude of the vector. 55 void Clamp(double max_mag) { 56 double mag = Magnitude(); 57 if (mag > max_mag) { 58 Scale(max_mag / mag); // Does Normalize() followed by Scale(max_mag). 59 } 60 } 61 62 // Compute the "heading" of a vector - this is the angle in radians between 63 // the vector and the x-axis. 64 // @return {!number} The "heading" angle in radians. 65 double Heading() const { 66 double angle = atan2(y_, x_); 67 return angle; 68 } 69 70 // Accessors and mutators for the coordinate values. 71 double x() const { return x_; } 72 void set_x(double x) { x_ = x; } 73 74 double y() const { return y_; } 75 void set_y(double y) { y_ = y; } 76 77 double x_; 78 double y_; 79 }; 80 81 #endif // VECTOR2_H_ 82
