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c:/home/kevn/src/animaniac/gator/TetherOperator.h

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#ifndef TETHER_OPER
#define TETHER_OPER
#include <vector>
#include "ani/Dynamics/Operator.h"
#include "ani/Dynamics/DynamicSystem.h"

namespace gator
{
   class TetherOperator : public ani::Operator<ani::Body>
   {
   public:
      typedef boost::shared_ptr<ani::Body> EntityTypePtr;

   public:
      TetherOperator( EntityTypePtr& e1, EntityTypePtr& e2 ) :
                                         ani::Operator<ani::Body>(),
                                         mE1( e1 ), mE2( e2 )
      {
      }
      
      virtual ~TetherOperator()
      {
      }

      void setEntities( EntityTypePtr& e1, EntityTypePtr& e2 )
      {
         mE1 = e1;
         mE2 = e2;
      }

      virtual void exec( ani::DynamicSystem<ani::Body>& ps, float timeDelta )
      {
         // make mE1 follow mE2
         //gmtl::Vec3f e2_dir( mE2->rotation() * gmtl::Vec3f( 0,0,-1 ) );
         gmtl::Vec3f distance_vec( mE2->position() - mE1->position() );
         float distance( gmtl::length( distance_vec ) );
         
         const float desired_distance = 6.0f;
         gmtl::Quatf target_rotation = mE2->rotation();
         gmtl::Vec3f target_position = target_rotation * gmtl::Vec3f( 0,0,-1 ) * (-desired_distance);
         target_position += mE2->position();
         
         //std::cout << target_rotation << " " << target_position << std::endl;
         
         const float max_distance = 12.0f;
         gmtl::Quatf rot;
         gmtl::Vec3f pos;
         float slerp_speed = 0;
         if (distance < max_distance)
            slerp_speed = 5.0f * timeDelta; // catch up slow!
         else if (distance >= max_distance)
            slerp_speed = 9.0f * timeDelta; // catch up fast!
         
         if (slerp_speed > 1.0f) slerp_speed = 1.0f;
         gmtl::slerp( rot, slerp_speed, mE1->rotation(), target_rotation );
         gmtl::lerp( pos, slerp_speed, mE1->position(), target_position );
         mE1->setPosition( pos );
         mE1->setRotation( rot );
      }

   private:
      EntityTypePtr& mE1;
      EntityTypePtr& mE2;
   };
} // end namespace gator

#endif

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