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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_PULLEY_JOINT_H
#define B2_PULLEY_JOINT_H
#include "b2_api.h"
#include "b2_joint.h"
const float b2_minPulleyLength = 2.0f;
/// Pulley joint definition. This requires two ground anchors,
/// two dynamic body anchor points, and a pulley ratio.
struct B2_API b2PulleyJointDef : public b2JointDef
{
b2PulleyJointDef()
{
type = e_pulleyJoint;
groundAnchorA.Set(-1.0f, 1.0f);
groundAnchorB.Set(1.0f, 1.0f);
localAnchorA.Set(-1.0f, 0.0f);
localAnchorB.Set(1.0f, 0.0f);
lengthA = 0.0f;
lengthB = 0.0f;
ratio = 1.0f;
collideConnected = true;
}
/// Initialize the bodies, anchors, lengths, max lengths, and ratio using the world anchors.
void Initialize(b2Body* bodyA, b2Body* bodyB,
const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
const b2Vec2& anchorA, const b2Vec2& anchorB,
float ratio);
/// The first ground anchor in world coordinates. This point never moves.
b2Vec2 groundAnchorA;
/// The second ground anchor in world coordinates. This point never moves.
b2Vec2 groundAnchorB;
/// The local anchor point relative to bodyA's origin.
b2Vec2 localAnchorA;
/// The local anchor point relative to bodyB's origin.
b2Vec2 localAnchorB;
/// The a reference length for the segment attached to bodyA.
float lengthA;
/// The a reference length for the segment attached to bodyB.
float lengthB;
/// The pulley ratio, used to simulate a block-and-tackle.
float ratio;
};
/// The pulley joint is connected to two bodies and two fixed ground points.
/// The pulley supports a ratio such that:
/// length1 + ratio * length2 <= constant
/// Yes, the force transmitted is scaled by the ratio.
/// Warning: the pulley joint can get a bit squirrelly by itself. They often
/// work better when combined with prismatic joints. You should also cover the
/// the anchor points with static shapes to prevent one side from going to
/// zero length.
class B2_API b2PulleyJoint : 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;
/// Get the first ground anchor.
b2Vec2 GetGroundAnchorA() const;
/// Get the second ground anchor.
b2Vec2 GetGroundAnchorB() const;
/// Get the current length of the segment attached to bodyA.
float GetLengthA() const;
/// Get the current length of the segment attached to bodyB.
float GetLengthB() const;
/// Get the pulley ratio.
float GetRatio() const;
/// Get the current length of the segment attached to bodyA.
float GetCurrentLengthA() const;
/// Get the current length of the segment attached to bodyB.
float GetCurrentLengthB() const;
/// Dump joint to dmLog
void Dump() override;
/// Implement b2Joint::ShiftOrigin
void ShiftOrigin(const b2Vec2& newOrigin) override;
protected:
friend class b2Joint;
b2PulleyJoint(const b2PulleyJointDef* data);
void InitVelocityConstraints(const b2SolverData& data) override;
void SolveVelocityConstraints(const b2SolverData& data) override;
bool SolvePositionConstraints(const b2SolverData& data) override;
b2Vec2 m_groundAnchorA;
b2Vec2 m_groundAnchorB;
float m_lengthA;
float m_lengthB;
// Solver shared
b2Vec2 m_localAnchorA;
b2Vec2 m_localAnchorB;
float m_constant;
float m_ratio;
float m_impulse;
// Solver temp
int32 m_indexA;
int32 m_indexB;
b2Vec2 m_uA;
b2Vec2 m_uB;
b2Vec2 m_rA;
b2Vec2 m_rB;
b2Vec2 m_localCenterA;
b2Vec2 m_localCenterB;
float m_invMassA;
float m_invMassB;
float m_invIA;
float m_invIB;
float m_mass;
};
#endif
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