www.pudn.com > Sterren_ASe_Explorer.rar > ase_losscan.h

/* Copyright (C) William van der Sterren, 2002.  
 * All rights reserved worldwide. 
 * 
 * This software is provided "as is" without express or implied 
 * warranties. You may freely copy and compile this source into 
 * applications you distribute provided that the copyright text 
 * below is included in the resulting source code, for example: 
 * "Portions Copyright (C) William van der Sterren, 2002" 
 */ 
 
/***************************************************************************   
 *                                                                             
 *     purpose: class to compute and record sector-based line-of-sight info 
*/ 
 
 
#ifndef _ASE_LOSSCAN_H_ 
#define _ASE_LOSSCAN_H_ 
 
#if _MSC_VER > 1000 
#pragma once 
#endif 
 
 
#include "ase_coordpair.h" 
 
 
/*! 
    ASE_LineOfSightScan uses 16 bits to store an approximation of true line of sight 
    from surrounding positions to this position, for 2D terrain.  
    The terrain surrounding this position is partitioned in 8 sectors of 45 degrees  
    each. 
 
    For each of the sectors, one of the following values is stored: 
    - 00 == eNotObserved 
    - 11 == eObservedFromFarDistance 
    - 10 == eObservedFromMediumDistance 
    - 01 == eObservedFromNearDistance 
    where (obviously) eObservedFromFarDistance also implies eObservedFromMediumDistance, 
    and eObservedFromMediumDistance implies eObservedFromNearDistance. 
 
    Given a future threat position, a vector from that position to this position is 
    computed, and a given the length and angle of the vector, the appropriate value 
    is retrieved. 
*/ 
 
class ASE_LineOfSightScan 
{ 
  public: 
    ASE_LineOfSightScan();  //!< inits to no cover 
 
    enum ScanValue 
      { 
        eNotObserved                = 0, 
        eObservedFromFarDistance    = 1, 
        eObservedFromMediumDistance = 2, 
        eObservedFromNearDistance   = 3 
      }; 
 
    void         ComputeLOSApproximation 
                       (int                  thisPositionX,  
                        int                  thisPositionY,  
                        const CoordPairList& thePositionsObservingThisPosition 
                       ); 
    void         Clear(); 
    void         SetNoCoverAtAll(); 
    void         UpdateSector(unsigned int aSector, ScanValue aValue); 
 
    ScanValue    GetObservationFromPosition(int thisPositionX, 
                                            int thisPositionY, 
                                            int theObserverX, 
                                            int theObserverY 
                                           ) const; 
 
    static bool  IsANearDistanceSqrd(int theDistanceSquared); 
    static bool  IsAMediumDistanceSqrd(int theDistanceSquared); 
    static bool  IsAFarDistanceSqrd(int theDistanceSquared); 
    static bool  IsOutOfReachSqrd(int theDistanceSquared); 
 
    static unsigned int GetNumberOfSectors(); 
 
 
    static void  SetThreatReachDistance(int theDistance); 
 
    static unsigned int GetSectorForLine(int deltaX, int deltaY); 
 
  protected: 
    typedef unsigned short int word; 
 
    static word         GetValueForSector(word aValue, unsigned int aSector); 
    static word         SetValueForSector(word aValue, word aSectorValue, unsigned int aSector); 
 
    word m_LOSDirections; 
 
  protected: 
    static int                m_kOutOfReachDistance; 
    static int                m_kFarDistance; 
    static int                m_kMediumDistance; 
 
    static const unsigned int m_kNumberOfSectors; 
    static const float        m_kSectorWidthInDegrees; 
}; 
 
 
#endif // _ASE_LOSSCAN_H_