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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"
/// Distance joint definition. This requires defining an anchor point on both
/// bodies and the non-zero distance of the distance joint. The definition uses
/// local anchor points so that the initial configuration can violate the
/// constraint slightly. This helps when saving and loading a game.
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;
}
/// Initialize the bodies, anchors, and rest length using world space anchors.
/// The minimum and maximum lengths are set to the rest length.
void Initialize(b2Body* bodyA, b2Body* bodyB,
const b2Vec2& anchorA, const b2Vec2& anchorB);
/// The local anchor point relative to bodyA's origin.
b2Vec2 localAnchorA;
/// The local anchor point relative to bodyB's origin.
b2Vec2 localAnchorB;
/// The rest length of this joint. Clamped to a stable minimum value.
float length;
/// Minimum length. Clamped to a stable minimum value.
float minLength;
/// Maximum length. Must be greater than or equal to the minimum length.
float maxLength;
/// The linear stiffness in N/m.
float stiffness;
/// The linear damping in N*s/m.
float damping;
};
/// A distance joint constrains two points on two bodies to remain at a fixed
/// distance from each other. You can view this as a massless, rigid rod.
class B2_API b2DistanceJoint : public b2Joint
{
public:
b2Vec2 GetAnchorA() const override;
b2Vec2 GetAnchorB() const override;
/// Get the reaction force given the inverse time step.
/// Unit is N.
b2Vec2 GetReactionForce(float inv_dt) const override;
/// Get the reaction torque given the inverse time step.
/// Unit is N*m. This is always zero for a distance joint.
float GetReactionTorque(float 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 rest length
float GetLength() const { return m_length; }
/// Set the rest length
/// @returns clamped rest length
float SetLength(float length);
/// Get the minimum length
float GetMinLength() const { return m_minLength; }
/// Set the minimum length
/// @returns the clamped minimum length
float SetMinLength(float minLength);
/// Get the maximum length
float GetMaxLength() const { return m_maxLength; }
/// Set the maximum length
/// @returns the clamped maximum length
float SetMaxLength(float maxLength);
/// Get the current length
float GetCurrentLength() const;
/// Set/get the linear stiffness in N/m
void SetStiffness(float stiffness) { m_stiffness = stiffness; }
float GetStiffness() const { return m_stiffness; }
/// Set/get linear damping in N*s/m
void SetDamping(float damping) { m_damping = damping; }
float GetDamping() const { return m_damping; }
/// Dump joint to dmLog
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
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