/********************************************************************
**                Image Component Library (ICL)                    **
**                                                                 **
** Copyright (C) 2006-2012 CITEC, University of Bielefeld          **
**                         Neuroinformatics Group                  **
** Website: www.iclcv.org and                                      **
**          http://opensource.cit-ec.de/projects/icl               **
**                                                                 **
** File   : include/ICLGeom/ViewRay.h                              **
** Module : ICLGeom                                                **
** Authors: Christof Elbrechter                                    **
**                                                                 **
**                                                                 **
** Commercial License                                              **
** ICL can be used commercially, please refer to our website       **
** www.iclcv.org for more details.                                 **
**                                                                 **
** GNU General Public License Usage                                **
** Alternatively, this file may be used under the terms of the     **
** GNU General Public License version 3.0 as published by the      **
** Free Software Foundation and appearing in the file LICENSE.GPL  **
** included in the packaging of this file.  Please review the      **
** following information to ensure the GNU General Public License  **
** version 3.0 requirements will be met:                           **
** http://www.gnu.org/copyleft/gpl.html.                           **
**                                                                 **
** The development of this software was supported by the           **
** Excellence Cluster EXC 277 Cognitive Interaction Technology.    **
** The Excellence Cluster EXC 277 is a grant of the Deutsche       **
** Forschungsgemeinschaft (DFG) in the context of the German       **
** Excellence Initiative.                                          **
**                                                                 **
*********************************************************************/

#ifndef ICL_VIEW_RAY_H
#define ICL_VIEW_RAY_H

#include <ICLGeom/GeomDefs.h>
#include <ICLUtils/Exception.h>
#include <iostream>

namespace icl{
  /** \cond */
  class PlaneEquation;
  /** \endcond */

  /// This is a view-ray's line equation in parameter form
  /** A view-ray is described by the equation
      \f[ V: \mbox{offset} + \lambda \cdot \mbox{direction} \f]
  */
  struct ViewRay{
    /// Constructor with given offset and direction vector
    explicit ViewRay(const Vec &offset=Vec(), const Vec &direction=Vec(), bool autoNormalizeDirection=false);
    
    /// line offset
    Vec offset;
    
    /// line direction
    Vec direction;
    
    /// calculates line-plane intersection 
    /** @see static Camera::getIntersection function */
    Vec getIntersection(const PlaneEquation &plane) const throw (ICLException);
    
    /// calculates the closest distance to the given 3D-Point
    /** for following formula is used:
        <pre>
        ViewRay: o + lambda * v;
        3D-Point: p
        
        distance = sqrt( |p-o|^2 - |(p-o).v|^2 )
        </pre>
    */
    float closestDistanceTo(const Vec &p) const;
    
    /// calculates the closes distance to the given other ViewRay
    /** Here, we use the following formula:
        <pre>
        this ViewRay:  o + lambda * v
        other ViewRay: k + beta * m
        
        distance = | (k-o).(v x m) | 
                   -----------------
                       | v x m |
        </pre>
    */
    float closestDistanceTo(const ViewRay &other) const;
    
    /// evaluates ViewRay' line equation at given lambda
    /** formula : offset + lambda * direction */
    Vec operator()(float lambda) const;
  };

  /// ostream operator
  std::ostream &operator<<(std::ostream &s, const ViewRay &vr);
}

#endif