b2_distance_joint.h

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// 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