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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_MOUSE_JOINT_H
#define B2_MOUSE_JOINT_H
#include "b2_api.h"
#include "b2_joint.h"
/// Mouse joint definition. This requires a world target point,
/// tuning parameters, and the time step.
struct B2_API b2MouseJointDef : public b2JointDef
{
b2MouseJointDef()
{
type = e_mouseJoint;
target.Set(0.0f, 0.0f);
maxForce = 0.0f;
stiffness = 0.0f;
damping = 0.0f;
}
/// The initial world target point. This is assumed
/// to coincide with the body anchor initially.
b2Vec2 target;
/// The maximum constraint force that can be exerted
/// to move the candidate body. Usually you will express
/// as some multiple of the weight (multiplier * mass * gravity).
float maxForce;
/// The linear stiffness in N/m
float stiffness;
/// The linear damping in N*s/m
float damping;
};
/// A mouse joint is used to make a point on a body track a
/// specified world point. This a soft constraint with a maximum
/// force. This allows the constraint to stretch and without
/// applying huge forces.
/// NOTE: this joint is not documented in the manual because it was
/// developed to be used in the testbed. If you want to learn how to
/// use the mouse joint, look at the testbed.
class B2_API b2MouseJoint : public b2Joint
{
public:
/// Implements b2Joint.
b2Vec2 GetAnchorA() const override;
/// Implements b2Joint.
b2Vec2 GetAnchorB() const override;
/// Implements b2Joint.
b2Vec2 GetReactionForce(float inv_dt) const override;
/// Implements b2Joint.
float GetReactionTorque(float inv_dt) const override;
/// Use this to update the target point.
void SetTarget(const b2Vec2& target);
const b2Vec2& GetTarget() const;
/// Set/get the maximum force in Newtons.
void SetMaxForce(float force);
float GetMaxForce() 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; }
/// The mouse joint does not support dumping.
void Dump() override { b2Log("Mouse joint dumping is not supported.\n"); }
/// Implement b2Joint::ShiftOrigin
void ShiftOrigin(const b2Vec2& newOrigin) override;
protected:
friend class b2Joint;
b2MouseJoint(const b2MouseJointDef* def);
void InitVelocityConstraints(const b2SolverData& data) override;
void SolveVelocityConstraints(const b2SolverData& data) override;
bool SolvePositionConstraints(const b2SolverData& data) override;
b2Vec2 m_localAnchorB;
b2Vec2 m_targetA;
float m_stiffness;
float m_damping;
float m_beta;
// Solver shared
b2Vec2 m_impulse;
float m_maxForce;
float m_gamma;
// Solver temp
int32 m_indexA;
int32 m_indexB;
b2Vec2 m_rB;
b2Vec2 m_localCenterB;
float m_invMassB;
float m_invIB;
b2Mat22 m_mass;
b2Vec2 m_C;
};
#endif
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