VPhysics: rigid bodies, constraints, ragdolls, and vehicles

// vphysics/physics_environment.h
class CPhysicsEnvironment : public IPhysicsEnvironment
{
public:
    // Object creation
    IPhysicsObject *CreatePolyObject( const CPhysCollide *pCollisionModel,
        int materialIndex, const Vector &position,
        const QAngle &angles, objectparams_t *pParams );

    // Simulation
    void Simulate( float deltaTime );
    void SetGravity( const Vector &gravityVector );
    float GetSimulationTimestep() const;
    void SetSimulationTimestep( float timestep );

    // Constraints
    IPhysicsConstraint *CreateHingeConstraint( ... );
    IPhysicsConstraint *CreateRagdollConstraint( ... );
    IPhysicsConstraint *CreateFixedConstraint( ... );
    IPhysicsConstraint *CreateSpring( ... );
};

// Applying an impulse (e.g., explosion force)
IPhysicsObject *pPhys = pEntity->VPhysicsGetObject();
if ( pPhys )
{
    Vector impulse = direction * force;  // kg*in/s
    pPhys->ApplyForceCenter( impulse );
}

// game/server/physics_prop_ragdoll.h
class CRagdollProp : public CBaseAnimating, public CDefaultPlayerPickupVPhysics
{
public:
    void InitRagdoll( const Vector &forceVector, int forceBone,
        const matrix3x4_t *pDeltaBones0, const matrix3x4_t *pDeltaBones1,
        float dt, int collisionGroup, bool activateRagdoll );

    ragdoll_t   m_ragdoll;   // array of physics objects + constraints
};