/***************************************************************************
   File:        PBMSpringMass.h                                                            
   Created:     02/12/2002                                                            
   Author:      Maxim Garber                                                
                Computer Science Department                                 
                University of North Carolina - Chapel Hill                  
                garber@cs.unc.edu                                           
                                                                            
   Description: Spring for physically based modelling simulation.                                                            
                                                                            
----------------------------------------------------------------------------.
   Copyright 2002 Maxim Garber                                              
   UNC Collide Research Group                                       
                                                                            
                                                                            
*****************************************************************************/
#include "PBMSimObject.h"
#include "ODESolver.h"
#include "PBMSpringMassParams.h"

class PBMSpringMass: 
// inherits from SimObject and ODESystem base classes
public PBMSimObject, public ODESystem
{
public:
  PBMSpringMass(PBMSpringMassParams params);
  ~PBMSpringMass(){};

  //////////////////////////////////////////////////////////////////////////////
  // Simulation 
  void Update(float timeStep);

  //////////////////////////////////////////////////////////////////////////////
  // mutators
  void SetRestLength    (float restLength     ){_restLength = restLength;        }
  void SetSpringConstant(float springConstant ){_springConstant = springConstant;}
  void SetMass          (float mass           ){_mass = mass;                    }
  void SetFriction      (float friction       ){_friction = friction;            }
  void SetIntegrator    (ODESolver* integrator){_integrator = integrator;        }

  //////////////////////////////////////////////////////////////////////////////
  // Rendering
  void Draw();

  //////////////////////////////////////////////////////////////////////////////
  // Test For Culling
  bool IsActive(){return true;}

  //////////////////////////////////////////////////////////////////////////////
  // ODE Integration
  void ODEDerivative(const ODEConfig& config, float time, ODEConfig& derivative);

private:
  // state
  float _anchor  [3];
  float _position[3];
  float _velocity[3];
  float _restLength;
  float _springConstant;
  float _mass;

  // forces
  float _gravity[3];          // force of gravity
  float _friction;            // air friction
  float _externalForce[3];    // external forces acting on projectile

  // ODE solver
  ODESolver* _integrator;
};