Rotation2D.h

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/**
 *  \file IMP/algebra/Rotation2D.h
 *  \brief Classes and operations related with rotations
 *
 *  Copyright 2007-2013 IMP Inventors. All rights reserved.
*/

#ifndef IMPALGEBRA_ROTATION_2D_H
#define IMPALGEBRA_ROTATION_2D_H

#include <IMP/algebra/algebra_config.h>
#include "utility.h"
#include "Vector2D.h"
#include "GeometricPrimitiveD.h"
#include "constants.h"
#include <cmath>
//#include <stdlib.h>

IMPALGEBRA_BEGIN_NAMESPACE

#if !defined(IMP_DOXYGEN) && !defined(SWIG)
class Rotation2D;
Rotation2D compose(const Rotation2D &a, const Rotation2D &b);
#endif

//! Stores a 2D rotation matrix
/**
  \note This class requires the angles to be given in radians, and the
  convention used is that the rotations are performed rotating counterclockwise
  (right hand side convention).

  \geometry
**/
class Rotation2D : public GeometricPrimitiveD<2> {
 public:
  Rotation2D() : angle_(std::numeric_limits<double>::quiet_NaN()) {};

  //! Builds the matrix for the given angle
  Rotation2D(double angle) { set_angle(angle); }

  //! rotates a 2D point
  /**
  * \param[in] o a 2D vector to be rotated
  */
  Vector2D get_rotated(const Vector2D &o) const {
    IMP_INTERNAL_CHECK(!base::isnan(angle_),
                       "Attempting to use uninitialized rotation");
    return get_rotated(o[0], o[1]);
  }

  //! rotates a 2D point
  Vector2D get_rotated(const double x, const double y) const {
    IMP_INTERNAL_CHECK(!base::isnan(angle_),
                       "Attempting to use uninitialized rotation");
    return Vector2D(c_ * x - s_ * y, s_ * x + c_ * y);
  }

  //! Returns the matrix for the inverse rotation
  Rotation2D get_inverse() const {
    IMP_INTERNAL_CHECK(!base::isnan(angle_),
                       "Attempting to use uninitialized rotation");
    return Rotation2D(-angle_);
  }

  //! sets the angle for the rotation
  /**
  * \param[in] angle the angle
  */
  void set_angle(double angle) {
    angle_ = angle;
    c_ = cos(angle);
    s_ = sin(angle);
  }

  //! gets the angle
  double get_angle() const { return angle_; }

  //! Prints the angle
  IMP_SHOWABLE_INLINE(Rotation2D, out << "Rotation2D (radians): " << angle_;);

 private:
  double angle_;  // angle
  double c_;      // cosine of the angle
  double s_;      // sine of the angle
};

//! Builds an identity rotation in 2D
inline Rotation2D get_identity_rotation_2d() { return Rotation2D(0.0); }

//! Builds an identity rotation in 2D
inline Rotation2D get_random_rotation_2d() {
  return Rotation2D(2 * PI * ((double)rand() / ((double)RAND_MAX + 1)));
}

//! Builds the rotation that transforms the vector X of the origin
//! of coordinates into the given vector
inline Rotation2D get_rotation_to_x_axis(const Vector2D &v) {
  return Rotation2D(atan2(v[1], v[0]));
}

//! compose two rotations a and b
/**
  For any vector v (a*b)*v = a*(b*v).
*/
inline Rotation2D compose(const Rotation2D &a, const Rotation2D &b) {
  double new_angle = a.get_angle() + b.get_angle();
  Rotation2D R(new_angle);
  return R;
}

IMP_VALUES(Rotation2D, Rotation2Ds);

IMPALGEBRA_END_NAMESPACE
#endif /* IMPALGEBRA_ROTATION_2D_H */