hkpDashpotAction.h
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- /*
- *
- * Confidential Information of Telekinesys Research Limited (t/a Havok). Not for disclosure or distribution without Havok's
- * prior written consent. This software contains code, techniques and know-how which is confidential and proprietary to Havok.
- * Level 2 and Level 3 source code contains trade secrets of Havok. Havok Software (C) Copyright 1999-2009 Telekinesys Research Limited t/a Havok. All Rights Reserved. Use of this software is subject to the terms of an end user license agreement.
- *
- */
- #ifndef HK_DASHPOT_H
- #define HK_DASHPOT_H
- #include <Physics/Dynamics/Action/hkpBinaryAction.h>
- #include <Physics/Dynamics/Entity/hkpRigidBody.h>
- extern const hkClass hkpDashpotActionClass;
- /// A dashpot is a simple version of a constraint that works like a heavily damped spring.
- /// You can use a dashpot to attach two bodies together, or a body to a point in world space.
- /// It is similar to a point-to-point constraint, although it is an hkpAction rather
- /// an hkpConstraintInstance.
- /// A dashpot works by applying forces to its object or objects in an attempt
- /// to keep the attachment points at the same position in world space.
- /// These attachment points are specified in the local space of the rigid bodies.
- /// Strong forces (such as a Mouse Spring) or impulses may momentarily break this constraint, but the bodies will
- /// automatically snap back to reinstate it.
- /// n
- /// In general, dashpots are faster than constraints, but have less stability.
- /// For example, high strength values can add instability to the system, and can cause the system
- /// to gain energy and even explode. It is advisable to have a strength that is equal to the heaviest
- /// rigid body - for instance, if that body has a mass of 10 kg, a good value for strength
- /// is 10. It is also advisable to have a damping that is 1/10 the value of the strength.
- /// Values of much higher than this can make the system explode.n
- /// n
- /// The stability of the system is also linked to
- /// the size of the timesteps taken during simulation - a bigger timestep can make
- /// the system more unstable. A timestep of .01666 (60 Hz) with two or three
- /// substeps is generally required.
- ///
- /// param str The strength of the dashpot range[see notes] default==1
- /// param damp The damping coeffecient of the dashpot - this determines the rate of decay of oscillations of the dashpot. A good value for damping is 1/10 the value of the strength. range[see notes] default==0.1
- class hkpDashpotAction : public hkpBinaryAction
- {
- public:
- HK_DECLARE_REFLECTION();
- /// Creates a dashpot with the specified construction info.
- hkpDashpotAction(hkpRigidBody* entityA = HK_NULL, hkpRigidBody* entityB = HK_NULL, hkUlong userData = 0);
- /// Apply the hkpDashpotAction to the two bodies.
- /// A dashpot is an action and so it has an apply method. This method is called
- /// every timestep and applies the necessary impulses to ra and rb to achieve the
- /// dashpot motion.
- void applyAction(const hkStepInfo& stepInfo);
- /// Sets the attach points with world space information.
- /// Make sure to set the body pointers before calling this function.
- inline void setInWorldSpace(const hkVector4& pivotA, const hkVector4& pivotB);
- /// Sets the attach points with local space information.
- inline void setInBodySpace(const hkVector4& pivotA, const hkVector4& pivotB);
- /// Gets the point of attachment to body A, in body A space.
- inline const hkVector4& getPointA() const;
- ///Gets the point of attachment to body B, in body B space
- inline const hkVector4& getPointB() const;
- /// Sets the point of attachment to body A, in body A space.
- inline void setPointA(const hkVector4& pa);
- ///Sets the point of attachment to body B, in body B space
- inline void setPointB(const hkVector4& pb);
- /// Return positions in local space on bodies A and B to which the hkpDashpotAction is attached.
- /// param pa The hkpDashpotAction application point on bodyA, in the local space of bodyA, are copied into pa.
- /// param pb The hkpDashpotAction application point on bodyB, in the local space of bodyB, are copied into pb.
- inline void getPoints(hkVector4& pa, hkVector4& pb);
- /// Dynamically change points (in local space) on bodies A and B to which the hkpDashpotAction is attached.
- /// param pa The position of the point on bodyA in the local space of bodyA.
- /// param pb The position of the point on bodyB in the local space of bodyB.
- inline void setPoints(const hkVector4& pa, const hkVector4& pb);
- /// Returns the strength of the hkpDashpotAction.
- /// This value is the strength of the restoring force between the two points. An appropriate strength for
- /// a hkpDashpotAction is the weight of the heavier of the two rigid bodies.
- inline hkReal getStrength() const;
- /// Dynamically sets the strength of the hkpDashpotAction.
- /// This value is the strength of the restoring force between the two points. An appropriate strength for a
- /// hkpDashpotAction is the weight of the heavier of the two rigid bodies
- /// param s The new strength.
- inline void setStrength(hkReal s);
- /// Returns the damping coefficient of the hkpDashpotAction.
- /// The damping parameter specifies the rate of decay of the oscillations the hkpDashpotAction produces.
- /// Values higher than 1/10 of the hkpDashpotAction strength can cause instability.
- inline hkReal getDamping() const;
- /// Dynamically sets the damping coefficient of the hkpDashpotAction.
- /// The damping parameter specifies the rate of decay of the oscillations the hkpDashpotAction produces.
- /// In general the damping should be 10% of the strength of the hkpDashpotAction.
- /// param d The damping coefficient of the hkpDashpotAction.
- inline void setDamping(hkReal d);
- /// This function returns the last impulse has been applied to the bodies by the dashpot.
- inline const hkVector4 & getImpulse();
- /// hkpAction clone interface.
- virtual hkpAction* clone( const hkArray<hkpEntity*>& newEntities, const hkArray<hkpPhantom*>& newPhantoms ) const;
- protected:
- hkVector4 m_point[2];
- hkReal m_strength;
- hkReal m_damping;
- hkVector4 m_impulse;
- public:
- hkpDashpotAction( class hkFinishLoadedObjectFlag flag ) : hkpBinaryAction(flag) {}
- };
- #include <Physics/Utilities/Actions/Dashpot/hkpDashpotAction.inl>
- #endif // HAVOK_DASHPO
- /*
- * Havok SDK - NO SOURCE PC DOWNLOAD, BUILD(#20090216)
- *
- * Confidential Information of Havok. (C) Copyright 1999-2009
- * Telekinesys Research Limited t/a Havok. All Rights Reserved. The Havok
- * Logo, and the Havok buzzsaw logo are trademarks of Havok. Title, ownership
- * rights, and intellectual property rights in the Havok software remain in
- * Havok and/or its suppliers.
- *
- * Use of this software for evaluation purposes is subject to and indicates
- * acceptance of the End User licence Agreement for this product. A copy of
- * the license is included with this software and is also available at www.havok.com/tryhavok.
- *
- */