PulleyJoint.h

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#ifndef PULLEY_JOINT_H
#define PULLEY_JOINT_H
 
#include "PxPhysicsAPI.h"
 
// a pulley joint constrains two actors such that the sum of their distances from their respective anchor points at their attachment points 
// is a fixed value (the parameter 'distance'). Only dynamic actors are supported.
//
// The constraint equation is as follows:
//
// |anchor0 - attachment0| + |anchor1 - attachment1| * ratio = distance
// 
// where 'ratio' provides mechanical advantage.
//
// The above equation results in a singularity when the anchor point is coincident with the attachment point; for simplicity
// the constraint does not attempt to handle this case robustly.
 
class PulleyJoint : public physx::PxConstraintConnector
{
public:
 
    static const physx::PxU32 TYPE_ID = physx::PxConcreteType::eFIRST_USER_EXTENSION;
 
    PulleyJoint(physx::PxPhysics& physics, 
                physx::PxRigidBody& body0, const physx::PxTransform& localFrame0, const physx::PxVec3& attachment0,
                physx::PxRigidBody& body1, const physx::PxTransform& localFrame1, const physx::PxVec3& attachment1);
 
    void release();
 
    // attribute accessor and mutators
 
    void            setAttachment0(const physx::PxVec3& pos);
    physx::PxVec3   getAttachment0() const;
 
    void            setAttachment1(const physx::PxVec3& pos);
    physx::PxVec3   getAttachment1() const;
 
    void            setDistance(physx::PxReal totalDistance);
    physx::PxReal   getDistance() const;
    
    void            setRatio(physx::PxReal ratio);
    physx::PxReal   getRatio() const;
 
    // PxConstraintConnector boilerplate
 
    void*           prepareData();
    void            onConstraintRelease();
    void            onComShift(physx::PxU32 actor);
    void            onOriginShift(const physx::PxVec3& shift);
    void*           getExternalReference(physx::PxU32& typeID);
 
    bool            updatePvdProperties(physx::pvdsdk::PvdDataStream&,
                                        const physx::PxConstraint*,
                                        physx::PxPvdUpdateType::Enum) const { return true; }
    void            updateOmniPvdProperties() const { }
    physx::PxBase*  getSerializable() { return NULL; }
 
    virtual physx::PxConstraintSolverPrep getPrep() const;
 
    virtual const void* getConstantBlock() const { return &mData; }
 
    struct PulleyJointData
    {
        physx::PxTransform c2b[2];
    
        physx::PxVec3 attachment0;
        physx::PxVec3 attachment1;
 
        physx::PxReal distance;
        physx::PxReal ratio;
        physx::PxReal tolerance;
    };
 
    physx::PxRigidBody*     mBody[2];
    physx::PxTransform      mLocalPose[2];
 
    physx::PxConstraint*    mConstraint;
    PulleyJointData         mData;
 
    ~PulleyJoint() {}
};
 
#endif