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DT_Sphere.cpp

/*
 * SOLID - Software Library for Interference Detection
 * 
 * Copyright (C) 2001-2003  Dtecta.  All rights reserved.
 *
 * This library may be distributed under the terms of the Q Public License
 * (QPL) as defined by Trolltech AS of Norway and appearing in the file
 * LICENSE.QPL included in the packaging of this file.
 *
 * This library may be distributed and/or modified under the terms of the
 * GNU General Public License (GPL) version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * This library is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Commercial use or any other use of this library not covered by either 
 * the QPL or the GPL requires an additional license from Dtecta. 
 * Please contact info@dtecta.com for enquiries about the terms of commercial
 * use of this library.
 */

#include "DT_Sphere.h"
#include "GEN_MinMax.h"

MT_Scalar DT_Sphere::supportH(const MT_Vector3& v) const 
{
      return m_radius * v.length();
}

MT_Point3 DT_Sphere::support(const MT_Vector3& v) const 
{
   MT_Scalar s = v.length();
      
      if (s > MT_Scalar(0.0))
      {
            s = m_radius / s;
            return MT_Point3(v[0] * s, v[1] * s, v[2] * s);
      }
      else
      {
            return MT_Point3(m_radius, MT_Scalar(0.0), MT_Scalar(0.0));
      }
}

bool DT_Sphere::ray_cast(const MT_Point3& source, const MT_Point3& target,
                                     MT_Scalar& param, MT_Vector3& normal) const 
{
      MT_Vector3 r = target - source;
      MT_Scalar  delta = -source.dot(r);  
      MT_Scalar  r_length2 = r.length2();
      MT_Scalar  sigma = delta * delta - r_length2 * (source.length2() - m_radius * m_radius);

      if (sigma >= MT_Scalar(0.0))
            // The line trough source and target intersects the sphere.
      {
            MT_Scalar sqrt_sigma = MT_sqrt(sigma);
            // We need only the sign of lambda2, so the division by the positive 
            // r_length2 can be left out.
            MT_Scalar lambda2 = (delta + sqrt_sigma) /* / r_length2 */ ;
            if (lambda2 >= MT_Scalar(0.0))
                  // The ray points at the sphere
            {
                  MT_Scalar lambda1 = (delta - sqrt_sigma) / r_length2;
                  if (lambda1 <= param)
                        // The ray hits the sphere, since 
                        // [lambda1, lambda2] overlaps [0, param]. 
                  {
                        if (lambda1 > MT_Scalar(0.0))
                        {
                              param = lambda1;
                              normal = (source + r * lambda1) / m_radius;
                              // NB: division by m_radius to normalize the normal.
                        }
                        else
                        {
                              param = MT_Scalar(0.0);
                              normal.setValue(MT_Scalar(0.0), MT_Scalar(0.0), MT_Scalar(0.0));
                        }
                                    
                        return true;
                  }
            }
      }

      return false;
}



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