/******************************************************************************

   Use 'Joint' to link 2 actors together, or one actor to fixed position in world.

/******************************************************************************/
struct Spring
{
   Flt spring, damping;

   Spring(Flt spring=0, Flt damping=0) {T.spring=spring; T.damping=damping;}
};
/******************************************************************************/
struct Joint // a Joint between 2 actors, or one actor and fixed position in world
{
   // manage
   Joint& del            (                                                                                                                 ); // delete manually
   Joint& create         (Actor &a0, Actor *a1                                                                                             ); // create default   joint
   Joint& createHinge    (Actor &a0, Actor *a1, C Vec &anchor , C Vec &axis   ,                                        Bool collision=false); // create hinge     joint, 'anchor'=world space anchor position, 'axis'=world space joint axis, 'collision'=if allow for collisions between 'a0' and 'a1'
   Joint& createHinge    (Actor &a0, Actor *a1, C Vec &anchor , C Vec &axis   , Flt min_angle   , Flt max_angle      , Bool collision=false); // create hinge     joint, 'anchor'=world space anchor position, 'axis'=world space joint axis, 'collision'=if allow for collisions between 'a0' and 'a1'
   Joint& createSpherical(Actor &a0, Actor *a1, C Vec &anchor , C Vec &axis   , Flt *swing=null , Flt *twist=null    , Bool collision=false); // create spherical joint, 'anchor'=world space anchor position, 'axis'=world space joint axis, 'swing'=maximum allowed swing angle rotation (0..PI) null for no limits, 'twist'=maximum allowed twist angle rotation (0..PI) null for no limits
   Joint& createSliding  (Actor &a0, Actor *a1, C Vec &anchor , C Vec &dir    , Flt min, Flt max                     , Bool collision=false); // create sliding   joint, 'anchor'=world space anchor position, 'dir' =world space sliding direction, 'min'=minumum allowed distance along 'dir' (-Inf..'max'), 'max'=maximum allowed distance along 'dir' ('min'..Inf)
   Joint& createDist     (Actor &a0, Actor *a1, C Vec &anchor0, C Vec &anchor1, Flt min, Flt max, Spring *spring=null, Bool collision=false); // create distance based joint, here 'anchor0 anchor1' are in local spaces of actors

   Joint& createBodyHinge    (Actor &bone, Actor &parent, C Vec &anchor, C Vec &axis, Flt min_angle, Flt max_angle); // create body hinge     joint, 'anchor'=world space anchor position, 'axis'=world space joint axis, 'collision'=if allow for collisions between 'a0' and 'a1'
   Joint& createBodySpherical(Actor &bone, Actor &parent, C Vec &anchor, C Vec &axis, Flt swing    , Flt twist    ); // create body spherical joint, 'anchor'=world space anchor position, 'axis'=world space joint axis, 'swing'=maximum allowed swing angle rotation (0..PI), 'twist'=maximum allowed twist angle rotation (0..PI)

   // get / set
   Bool   is       (                             )C {return _joint!=null;} // if  created
   Bool   broken   (                             )C;                       // if  joint is broken
   Joint& breakable(Flt max_force, Flt max_torque) ;                       // set breakable parameters, if forces applied to the joint will exceed given parameters the joint will break (use <0 values for non-breakable joint)
#if EE_PRIVATE
   Matrix localAnchor(Bool index)C; // get anchor in actor local space (index=which actor), MatrixIdentity on fail
   void   changed();
#endif

   // hinge joint specific (following methods are supported only on PhysX)
	Flt  hingeAngle          ()C; // get joint angle in range (-PI, PI]
	Flt  hingeVel            ()C; // get joint velocity
   Bool hingeDriveEnabled   ()C;   Joint& hingeDriveEnabled   (Bool on   ); // get/set if drive is enabled
   Bool hingeDriveFreeSpin  ()C;   Joint& hingeDriveFreeSpin  (Bool on   ); // get/set if the existing velocity is beyond the drive velocity, do not add force
   Flt  hingeDriveVel       ()C;   Joint& hingeDriveVel       (Flt  vel  ); // get/set drive target velocity, 0..Inf, default=0
   Flt  hingeDriveForceLimit()C;   Joint& hingeDriveForceLimit(Flt  limit); // get/set the maximum torque the drive can exert, setting this to a very large value if 'hingeDriveVel' is also very large may cause unexpected results, 0..Inf, default=Inf
   Flt  hingeDriveGearRatio ()C;   Joint& hingeDriveGearRatio (Flt  ratio); // get/set the gear ratio for the drive, when setting up the drive constraint, the velocity of the first actor is scaled by this value, and its response to drive torque is scaled down. So if the drive target velocity is zero, the second actor will be driven to the velocity of the first scaled by the gear ratio. 0..Inf, default=1

   // io
   Bool save(File &f                      )C; // save, does not save information about which actors are joined, false on fail
   Bool load(File &f, Actor &a0, Actor *a1) ; // load, 'a0' and 'a1' are actors which the joint should link, false on fail

  ~Joint() {del();}
   Joint() {_joint=null;}

#if !EE_PRIVATE
private:
#endif
#if EE_PRIVATE
   PHYS_API(PxJoint, btTypedConstraint) *_joint;
#else
   Ptr _joint;
#endif

   NO_COPY_CONSTRUCTOR(Joint);
};
/******************************************************************************/