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/*
* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#ifndef B2_WELD_JOINT_H
#define B2_WELD_JOINT_H
#include "Box2D/Dynamics/Joints/b2Joint.h"
/// Weld joint definition. You need to specify local anchor points
/// where they are attached and the relative body angle. The position
/// of the anchor points is important for computing the reaction torque.
struct b2WeldJointDef : public b2JointDef
{
b2WeldJointDef()
{
type = e_weldJoint;
localAnchorA.Set(0.0f, 0.0f);
localAnchorB.Set(0.0f, 0.0f);
referenceAngle = 0.0f;
frequencyHz = 0.0f;
dampingRatio = 0.0f;
}
/// Initialize the bodies, anchors, and reference angle using a world
/// anchor point.
void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
/// The local anchor point relative to bodyA's origin.
b2Vec2 localAnchorA;
/// The local anchor point relative to bodyB's origin.
b2Vec2 localAnchorB;
/// The bodyB angle minus bodyA angle in the reference state (radians).
float32 referenceAngle;
/// The mass-spring-damper frequency in Hertz. Rotation only.
/// Disable softness with a value of 0.
float32 frequencyHz;
/// The damping ratio. 0 = no damping, 1 = critical damping.
float32 dampingRatio;
};
/// A weld joint essentially glues two bodies together. A weld joint may
/// distort somewhat because the island constraint solver is approximate.
class b2WeldJoint : public b2Joint
{
public:
b2Vec2 GetAnchorA() const override;
b2Vec2 GetAnchorB() const override;
b2Vec2 GetReactionForce(float32 inv_dt) const override;
float32 GetReactionTorque(float32 inv_dt) const override;
/// The local anchor point relative to bodyA's origin.
const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
/// The local anchor point relative to bodyB's origin.
const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
/// Get the reference angle.
float32 GetReferenceAngle() const { return m_referenceAngle; }
/// Set/get frequency in Hz.
void SetFrequency(float32 hz) { m_frequencyHz = hz; }
float32 GetFrequency() const { return m_frequencyHz; }
/// Set/get damping ratio.
void SetDampingRatio(float32 ratio) { m_dampingRatio = ratio; }
float32 GetDampingRatio() const { return m_dampingRatio; }
/// Dump to b2Log
void Dump() override;
protected:
friend class b2Joint;
b2WeldJoint(const b2WeldJointDef* def);
void InitVelocityConstraints(const b2SolverData& data) override;
void SolveVelocityConstraints(const b2SolverData& data) override;
bool SolvePositionConstraints(const b2SolverData& data) override;
float32 m_frequencyHz;
float32 m_dampingRatio;
float32 m_bias;
// Solver shared
b2Vec2 m_localAnchorA;
b2Vec2 m_localAnchorB;
float32 m_referenceAngle;
float32 m_gamma;
b2Vec3 m_impulse;
// Solver temp
int32 m_indexA;
int32 m_indexB;
b2Vec2 m_rA;
b2Vec2 m_rB;
b2Vec2 m_localCenterA;
b2Vec2 m_localCenterB;
float32 m_invMassA;
float32 m_invMassB;
float32 m_invIA;
float32 m_invIB;
b2Mat33 m_mass;
};
#endif
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