b2_distance_joint.h

// MIT License
 
// Copyright (c) 2019 Erin Catto
 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#ifndef B2_DISTANCE_JOINT_H
#define B2_DISTANCE_JOINT_H
 
#include "b2_api.h"
#include "b2_joint.h"
 
struct B2_API b2DistanceJointDef : public b2JointDef
{
    b2DistanceJointDef()
    {
        type = e_distanceJoint;
        localAnchorA.Set(0.0f, 0.0f);
        localAnchorB.Set(0.0f, 0.0f);
        length = 1.0f;
        minLength = 0.0f;
        maxLength = FLT_MAX;
        stiffness = 0.0f;
        damping = 0.0f;
    }
 
    void Initialize(b2Body* bodyA, b2Body* bodyB,
                    const b2Vec2& anchorA, const b2Vec2& anchorB);
 
    b2Vec2 localAnchorA;
 
    b2Vec2 localAnchorB;
 
    float length;
 
    float minLength;
 
    float maxLength;
 
    float stiffness;
 
    float damping;
};
 
class B2_API b2DistanceJoint : public b2Joint
{
public:
 
    b2Vec2 GetAnchorA() const override;
    b2Vec2 GetAnchorB() const override;
 
    b2Vec2 GetReactionForce(float inv_dt) const override;
 
    float GetReactionTorque(float inv_dt) const override;
 
    const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
 
    const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
 
    float GetLength() const { return m_length; }
 
    float SetLength(float length);
 
    float GetMinLength() const { return m_minLength; }
 
    float SetMinLength(float minLength);
 
    float GetMaxLength() const { return m_maxLength; }
 
    float SetMaxLength(float maxLength);
 
    float GetCurrentLength() const;
 
    void SetStiffness(float stiffness) { m_stiffness = stiffness; }
    float GetStiffness() const { return m_stiffness; }
 
    void SetDamping(float damping) { m_damping = damping; }
    float GetDamping() const { return m_damping; }
 
    void Dump() override;
 
    void Draw(b2Draw* draw) const override;
 
protected:
 
    friend class b2Joint;
    b2DistanceJoint(const b2DistanceJointDef* data);
 
    void InitVelocityConstraints(const b2SolverData& data) override;
    void SolveVelocityConstraints(const b2SolverData& data) override;
    bool SolvePositionConstraints(const b2SolverData& data) override;
 
    float m_stiffness;
    float m_damping;
    float m_bias;
    float m_length;
    float m_minLength;
    float m_maxLength;
 
    // Solver shared
    b2Vec2 m_localAnchorA;
    b2Vec2 m_localAnchorB;
    float m_gamma;
    float m_impulse;
    float m_lowerImpulse;
    float m_upperImpulse;
 
    // Solver temp
    int32 m_indexA;
    int32 m_indexB;
    b2Vec2 m_u;
    b2Vec2 m_rA;
    b2Vec2 m_rB;
    b2Vec2 m_localCenterA;
    b2Vec2 m_localCenterB;
    float m_currentLength;
    float m_invMassA;
    float m_invMassB;
    float m_invIA;
    float m_invIB;
    float m_softMass;
    float m_mass;
};
 
#endif