public override void Step(TimeStep step)
{
float timestep = step.Dt;
if (timestep <= Settings.FLT_EPSILON)
{
return;
}
if (timestep > MaxTimestep && MaxTimestep > 0)
{
timestep = MaxTimestep;
}
for (ControllerEdge i = _bodyList; i != null; i = i.nextBody)
{
Body body = i.body;
if (body.IsSleeping())
{
continue;
}
Vector2 damping = body.GetWorldVector(T.Multiply(body.GetLocalVector(body.GetLinearVelocity())));
body.SetLinearVelocity(body.GetLinearVelocity() + timestep * damping);
}
}
internal override void SolveVelocityConstraints(TimeStep step)
{
Body b = _body2;
Vector2 r = b.GetTransform().TransformDirection(_localAnchor - b.GetLocalCenter());
// Cdot = v + cross(w, r)
Vector2 Cdot = b._linearVelocity + r.CrossScalarPreMultiply(b._angularVelocity);
Vector2 impulse = _mass.Multiply(-(Cdot + _beta * _C + _gamma * _impulse));
Vector2 oldImpulse = _impulse;
_impulse += impulse;
float maxImpulse = step.Dt * _maxForce;
if (_impulse.LengthSquared() > maxImpulse * maxImpulse)
{
_impulse *= maxImpulse / _impulse.Length();
}
impulse = _impulse - oldImpulse;
b._linearVelocity += b._invMass * impulse;
b._angularVelocity += b._invI * r.Cross(impulse);
}
internal override bool SolvePositionConstraints(float baumgarte)
{
Body b1 = _body1;
Body b2 = _body2;
Vector2 c1 = b1._sweep.C;
float a1 = b1._sweep.A;
Vector2 c2 = b2._sweep.C;
float a2 = b2._sweep.A;
// Solve linear limit constraint.
float linearError = 0.0f, angularError = 0.0f;
bool active = false;
float C2 = 0.0f;
Mat22 R1 = new Mat22(a1), R2 = new Mat22(a2);
Vector2 r1 = R1.Multiply(_localAnchor1 - _localCenter1);
Vector2 r2 = R2.Multiply(_localAnchor2 - _localCenter2);
Vector2 d = c2 + r2 - c1 - r1;
if (_enableLimit)
{
_axis = R1.Multiply(_localXAxis1);
_a1 = (d + r1).Cross(_axis);
_a2 = r2.Cross(_axis);
float translation = Vector2.Dot(_axis, d);
if (System.Math.Abs(_upperTranslation - _lowerTranslation) < 2.0f * Settings.LinearSlop)
{
// Prevent large angular corrections
C2 = Box2DNet.Common.Math.Clamp(translation, -Settings.MaxLinearCorrection, Settings.MaxLinearCorrection);
linearError = Box2DNet.Common.Math.Abs(translation);
active = true;
}
else if (translation <= _lowerTranslation)
{
// Prevent large linear corrections and allow some slop.
C2 = Box2DNet.Common.Math.Clamp(translation - _lowerTranslation + Settings.LinearSlop, -Settings.MaxLinearCorrection, 0.0f);
linearError = _lowerTranslation - translation;
active = true;
}
else if (translation >= _upperTranslation)
{
// Prevent large linear corrections and allow some slop.
C2 = Box2DNet.Common.Math.Clamp(translation - _upperTranslation - Settings.LinearSlop, 0.0f, Settings.MaxLinearCorrection);
linearError = translation - _upperTranslation;
active = true;
}
}
_perp = R1.Multiply(_localYAxis1);
_s1 = (d + r1).Cross(_perp);
_s2 = r2.Cross(_perp);
Vector2 impulse;
float C1;
C1 = Vector2.Dot(_perp, d);
linearError = Box2DNet.Common.Math.Max(linearError, Box2DNet.Common.Math.Abs(C1));
angularError = 0.0f;
if (active)
{
float m1 = _invMass1, m2 = _invMass2;
float i1 = _invI1, i2 = _invI2;
float k11 = m1 + m2 + i1 * _s1 * _s1 + i2 * _s2 * _s2;
float k12 = i1 * _s1 * _a1 + i2 * _s2 * _a2;
float k22 = m1 + m2 + i1 * _a1 * _a1 + i2 * _a2 * _a2;
_K.Col1 = new Vector2(k11, k12);
_K.Col2 = new Vector2(k12, k22);
Vector2 C = new Vector2();
C.X = C1;
C.Y = C2;
impulse = _K.Solve(-C);
}
else
{
float m1 = _invMass1, m2 = _invMass2;
float i1 = _invI1, i2 = _invI2;
float k11 = m1 + m2 + i1 * _s1 * _s1 + i2 * _s2 * _s2;
float impulse1 = (-C1) / k11;
impulse.X = impulse1;
impulse.Y = 0.0f;
}
Vector2 P = impulse.X * _perp + impulse.Y * _axis;
float L1 = impulse.X * _s1 + impulse.Y * _a1;
float L2 = impulse.X * _s2 + impulse.Y * _a2;
c1 -= _invMass1 * P;
a1 -= _invI1 * L1;
c2 += _invMass2 * P;
a2 += _invI2 * L2;
// TODO_ERIN remove need for this.
b1._sweep.C = c1;
b1._sweep.A = a1;
b2._sweep.C = c2;
b2._sweep.A = a2;
b1.SynchronizeTransform();
b2.SynchronizeTransform();
return(linearError <= Settings.LinearSlop && angularError <= Settings.AngularSlop);
}
