native_client_sdk/src/examples/demo/flock/vector2.h

   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_