IntersectionPoints.cpp

#include "lifevariables.h"
#include "CScanner.h"

bool CScanner::GetIntersectionPoints( sPoint3f   *pBeginCoord, sPoint3f  *pEndCoord, 
                                      sPoint3f   eye,          sVector3f ray)
{
    _iXCount = 0;
    unsigned long mag0 = 0, mag1 = 0;

    GetXYIntersectionPoints(eye, ray);

    GetYZIntersectionPoints(eye, ray);

    GetXZIntersectionPoints(eye, ray);

    if ( _iXCount > 2 || _iXCount == 1 )
    {
        throw;
    }
    else if ( _iXCount == 0 )
    {
        return false;
    }
    else if ( _iXCount == 2 ) 
    {
        mag0 = _aIntersectionPoints[0].GetMagnitude();
        mag1 = _aIntersectionPoints[1].GetMagnitude();

        if (mag0 < mag1)
        {
            *pBeginCoord = _aIntersectionPoints[0].GetPoint();
            *pEndCoord   = _aIntersectionPoints[1].GetPoint();
        }
        else
        {
            *pBeginCoord = _aIntersectionPoints[1].GetPoint();
            *pEndCoord   = _aIntersectionPoints[0].GetPoint();        
        }
    }
    return true;
}

void CScanner::GetXYIntersectionPoints(sPoint3f   eye,sVector3f ray)
{
    sPoint3f xy_n,  xy_f;
    float    tp,    tm;

    /*
     * if z component of ray is 0, we're parallel to the x-y plane
     */
    if ( !ray.z )
    {
        return;
    }
    else
    {
        tp = ( _range.z - eye.z) / ray.z;
        tm = ( - _range.z - eye.z ) / ray.z;
    
        xy_n.x = eye.x + tm * ray.x;
        xy_n.y = eye.y + tm * ray.y;
        xy_n.z = eye.z + tm * ray.z;

        xy_f.x = eye.x + tp * ray.x;
        xy_f.y = eye.y + tp * ray.y;
        xy_f.z = eye.z + tp * ray.z;
    }

    /*
     * Test the near and far points to see if they fall within the volume
     */

    sPoint3f nearPoint( abs(xy_n.x) , abs(xy_n.y), abs(xy_n.z));
    sPoint3f farPoint( abs(xy_f.x), abs(xy_f.y), abs(xy_f.z));

    if ( nearPoint.x <= _range.x && 
         nearPoint.y <= _range.y &&
         nearPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

       _aIntersectionPoints[_iXCount++].Set(xy_n);
    }

    if ( farPoint.x <= _range.x && 
         farPoint.y <= _range.y &&
         farPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

        _aIntersectionPoints[_iXCount++].Set(xy_f);
    }

    return;
}

void CScanner::GetYZIntersectionPoints(sPoint3f   eye, sVector3f ray)
{
    sPoint3f yz_n,  yz_f;
    float    tp,    tm;

    /*
     * if x component of ray is 0, we're parallel to the y-z plane
     */
    if ( !ray.x )
    {
        return;
    }
    else
    {
        tp = ( _range.x - eye.x) / ray.x;
        tm = ( - _range.x - eye.x ) / ray.x;
    
        yz_n.x = eye.x + tm * ray.x;
        yz_n.y = eye.y + tm * ray.y;
        yz_n.z = eye.z + tm * ray.z;

        yz_f.x = eye.x + tp * ray.x;
        yz_f.y = eye.y + tp * ray.y;
        yz_f.z = eye.z + tp * ray.z;
    }

    /*
     * Test the near and far points to see if they fall within the volume
     */

    sPoint3f nearPoint( abs(yz_n.x) , abs(yz_n.y), abs(yz_n.z));
    sPoint3f farPoint( abs(yz_f.x), abs(yz_f.y), abs(yz_f.z));

    if ( nearPoint.x <= _range.x && 
         nearPoint.y <= _range.y &&
         nearPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

        _aIntersectionPoints[_iXCount++].Set(yz_n);
    }

    if ( farPoint.x <= _range.x && 
         farPoint.y <= _range.y &&
         farPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

        _aIntersectionPoints[_iXCount++].Set(yz_f);
    }
    
    return;
}

void CScanner::GetXZIntersectionPoints(sPoint3f   eye, sVector3f ray)
{
    sPoint3f xz_n,  xz_f;
    float    tp,    tm;

    /*
     * if y component of ray is 0, we're parallel to the x-z plane
     */
    if ( !ray.y )
    {
        return;
    }
    else
    {
        tp = ( _range.y - eye.y) / ray.y;
        tm = ( - _range.y - eye.y ) / ray.y;
    
        xz_n.x = eye.x + tm * ray.x;
        xz_n.y = eye.y + tm * ray.y;
        xz_n.z = eye.z + tm * ray.z;

        xz_f.x = eye.x + tp * ray.x;
        xz_f.y = eye.y + tp * ray.y;
        xz_f.z = eye.z + tp * ray.z;
    }

    /*
     * Test the near and far points to see if they fall within the volume
     */

    sPoint3f nearPoint( abs(xz_n.x) , abs(xz_n.y), abs(xz_n.z));
    sPoint3f farPoint( abs(xz_f.x), abs(xz_f.y), abs(xz_f.z));

    if ( nearPoint.x <= _range.x && 
         nearPoint.y <= _range.y &&
         nearPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

        _aIntersectionPoints[_iXCount++].Set(xz_n);
    }

    if ( farPoint.x <= _range.x && 
         farPoint.y <= _range.y &&
         farPoint.z <= _range.z    )
    {
        if ( _iXCount >= 2 )
            throw;

        _aIntersectionPoints[_iXCount++].Set(xz_f);
    }
    
    return;
}

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