public GearJoint(GearJointDef def) : base(def)
{
_jointA = def.JointA;
_jointB = def.JointB;
_typeA = _jointA.JointType;
_typeB = _jointB.JointType;
Debug.Assert(_typeA == JointType.Revolute || _typeA == JointType.Prismatic);
Debug.Assert(_typeB == JointType.Revolute || _typeB == JointType.Prismatic);
float coordinateA, coordinateB;
// TODO_ERIN there might be some problem with the joint edges in b2Joint.
_bodyC = _jointA.BodyA;
_bodyA = _jointA.BodyB;
// Body B on joint1 must be dynamic
Debug.Assert(_bodyA._type == BodyType.Dynamic);
// Get geometry of joint1
Transform xfA = _bodyA._xf;
float aA = _bodyA._sweep.A;
Transform xfC = _bodyC._xf;
float aC = _bodyC._sweep.A;
if (_typeA == JointType.Revolute)
{
RevoluteJoint revolute = (RevoluteJoint)def.JointA;
_localAnchorC = revolute._localAnchorA;
_localAnchorA = revolute._localAnchorB;
_referenceAngleA = revolute._referenceAngle;
_localAxisC = Vector2.Zero;
coordinateA = aA - aC - _referenceAngleA;
}
else
{
PrismaticJoint prismatic = (PrismaticJoint)def.JointA;
_localAnchorC = prismatic._localAnchorA;
_localAnchorA = prismatic._localAnchorB;
_referenceAngleA = prismatic._referenceAngle;
_localAxisC = prismatic._localXAxisA;
Vector2 pC = _localAnchorC;
Vector2 pA = MathUtils.MulT(xfC.q, MathUtils.Mul(xfA.q, _localAnchorA) + (xfA.p - xfC.p));
coordinateA = MathUtils.Dot(pA - pC, _localAxisC);
}
_bodyD = _jointB.BodyA;
_bodyB = _jointB.BodyB;
// Body B on joint2 must be dynamic
Debug.Assert(_bodyB._type == BodyType.Dynamic);
// Get geometry of joint2
Transform xfB = _bodyB._xf;
float aB = _bodyB._sweep.A;
Transform xfD = _bodyD._xf;
float aD = _bodyD._sweep.A;
if (_typeB == JointType.Revolute)
{
RevoluteJoint revolute = (RevoluteJoint)def.JointB;
_localAnchorD = revolute._localAnchorA;
_localAnchorB = revolute._localAnchorB;
_referenceAngleB = revolute._referenceAngle;
_localAxisD = Vector2.Zero;
coordinateB = aB - aD - _referenceAngleB;
}
else
{
PrismaticJoint prismatic = (PrismaticJoint)def.JointB;
_localAnchorD = prismatic._localAnchorA;
_localAnchorB = prismatic._localAnchorB;
_referenceAngleB = prismatic._referenceAngle;
_localAxisD = prismatic._localXAxisA;
Vector2 pD = _localAnchorD;
Vector2 pB = MathUtils.MulT(xfD.q, MathUtils.Mul(xfB.q, _localAnchorB) + (xfB.p - xfD.p));
coordinateB = MathUtils.Dot(pB - pD, _localAxisD);
}
_ratio = def.Ratio;
_constant = coordinateA + _ratio * coordinateB;
_impulse = 0.0f;
}
/// <summary>
/// Requires two existing revolute or prismatic joints (any combination will work). The provided joints must
/// attach a dynamic body to a static body.
/// </summary>
/// <param name="jointA">The first joint.</param>
/// <param name="jointB">The second joint.</param>
/// <param name="ratio">The ratio.</param>
/// <param name="bodyA">The first body</param>
/// <param name="bodyB">The second body</param>
public GearJoint(Body bodyA, Body bodyB, Joint jointA, Joint jointB, float ratio = 1f)
{
JointType = JointType.Gear;
BodyA = bodyA;
BodyB = bodyB;
JointA = jointA;
JointB = jointB;
Ratio = ratio;
_typeA = jointA.JointType;
_typeB = jointB.JointType;
Debug.Assert(_typeA == JointType.Revolute || _typeA == JointType.Prismatic || _typeA == JointType.FixedRevolute || _typeA == JointType.FixedPrismatic);
Debug.Assert(_typeB == JointType.Revolute || _typeB == JointType.Prismatic || _typeB == JointType.FixedRevolute || _typeB == JointType.FixedPrismatic);
float coordinateA, coordinateB;
// TODO_ERIN there might be some problem with the joint edges in b2Joint.
_bodyC = JointA.BodyA;
_bodyA = JointA.BodyB;
// Get geometry of joint1
Transform xfA = _bodyA._xf;
float aA = _bodyA._sweep.A;
Transform xfC = _bodyC._xf;
float aC = _bodyC._sweep.A;
if (_typeA == JointType.Revolute)
{
RevoluteJoint revolute = (RevoluteJoint)jointA;
_localAnchorC = revolute.LocalAnchorA;
_localAnchorA = revolute.LocalAnchorB;
_referenceAngleA = revolute.ReferenceAngle;
_localAxisC = Vector2.Zero;
coordinateA = aA - aC - _referenceAngleA;
}
else
{
PrismaticJoint prismatic = (PrismaticJoint)jointA;
_localAnchorC = prismatic.LocalAnchorA;
_localAnchorA = prismatic.LocalAnchorB;
_referenceAngleA = prismatic.ReferenceAngle;
_localAxisC = prismatic.LocalXAxis;
Vector2 pC = _localAnchorC;
Vector2 pA = MathUtils.MulT(xfC.q, MathUtils.Mul(xfA.q, _localAnchorA) + (xfA.p - xfC.p));
coordinateA = Vector2.Dot(pA - pC, _localAxisC);
}
_bodyD = JointB.BodyA;
_bodyB = JointB.BodyB;
// Get geometry of joint2
Transform xfB = _bodyB._xf;
float aB = _bodyB._sweep.A;
Transform xfD = _bodyD._xf;
float aD = _bodyD._sweep.A;
if (_typeB == JointType.Revolute)
{
RevoluteJoint revolute = (RevoluteJoint)jointB;
_localAnchorD = revolute.LocalAnchorA;
_localAnchorB = revolute.LocalAnchorB;
_referenceAngleB = revolute.ReferenceAngle;
_localAxisD = Vector2.Zero;
coordinateB = aB - aD - _referenceAngleB;
}
else
{
PrismaticJoint prismatic = (PrismaticJoint)jointB;
_localAnchorD = prismatic.LocalAnchorA;
_localAnchorB = prismatic.LocalAnchorB;
_referenceAngleB = prismatic.ReferenceAngle;
_localAxisD = prismatic.LocalXAxis;
Vector2 pD = _localAnchorD;
Vector2 pB = MathUtils.MulT(xfD.q, MathUtils.Mul(xfB.q, _localAnchorB) + (xfB.p - xfD.p));
coordinateB = Vector2.Dot(pB - pD, _localAxisD);
}
_ratio = ratio;
_constant = coordinateA + _ratio * coordinateB;
_impulse = 0.0f;
}