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MultiSphereShape.cpp

/*
 * Copyright (c) 2005 Erwin Coumans http://continuousphysics.com/Bullet/
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies.
 * Erwin Coumans makes no representations about the suitability 
 * of this software for any purpose.  
 * It is provided "as is" without express or implied warranty.
*/
#include "MultiSphereShape.h"
#include "CollisionShapes/CollisionMargin.h"
#include "SimdQuaternion.h"

MultiSphereShape::MultiSphereShape (const SimdVector3& inertiaHalfExtents,const SimdVector3* positions,const SimdScalar* radi,int numSpheres)
:m_inertiaHalfExtents(inertiaHalfExtents)
{
      m_minRadius = 1e30f;

      m_numSpheres = numSpheres;
      for (int i=0;i<m_numSpheres;i++)
      {
            m_localPositions[i] = positions[i];
            m_radi[i] = radi[i];
            if (radi[i] < m_minRadius)
                  m_minRadius = radi[i];
      }
      SetMargin(m_minRadius);

}



 
00035  SimdVector3      MultiSphereShape::LocalGetSupportingVertexWithoutMargin(const SimdVector3& vec0)const
{
      int i;
      SimdVector3 supVec(0,0,0);

      SimdScalar maxDot(-1e30f);


      SimdVector3 vec = vec0;
      SimdScalar lenSqr = vec.length2();
      if (lenSqr < 0.0001f)
      {
            vec.setValue(1,0,0);
      } else
      {
            float rlen = 1.f / SimdSqrt(lenSqr );
            vec *= rlen;
      }

      SimdVector3 vtx;
      SimdScalar newDot;

      const SimdVector3* pos = &m_localPositions[0];
      const SimdScalar* rad = &m_radi[0];

      for (i=0;i<m_numSpheres;i++)
      {
            vtx = (*pos) +vec*((*rad)-m_minRadius);
            pos++;
            rad++;
            newDot = vec.dot(vtx);
            if (newDot > maxDot)
            {
                  maxDot = newDot;
                  supVec = vtx;
            }
      }

      return supVec;

}










00086 void  MultiSphereShape::CalculateLocalInertia(SimdScalar mass,SimdVector3& inertia)
{
      //as an approximation, take the inertia of the box that bounds the spheres

      SimdTransform ident;
      ident.setIdentity();
//    SimdVector3 aabbMin,aabbMax;

//    GetAabb(ident,aabbMin,aabbMax);

      SimdVector3 halfExtents = m_inertiaHalfExtents;//(aabbMax - aabbMin)* 0.5f;

      float margin = CONVEX_DISTANCE_MARGIN;

      SimdScalar lx=2.f*(halfExtents[0]+margin);
      SimdScalar ly=2.f*(halfExtents[1]+margin);
      SimdScalar lz=2.f*(halfExtents[2]+margin);
      const SimdScalar x2 = lx*lx;
      const SimdScalar y2 = ly*ly;
      const SimdScalar z2 = lz*lz;
      const SimdScalar scaledmass = mass * 0.08333333f;

      inertia[0] = scaledmass * (y2+z2);
      inertia[1] = scaledmass * (x2+z2);
      inertia[2] = scaledmass * (x2+y2);

}




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