public TOISolverManifold(ref TOIConstraint cc, int index)
{
Debug.Assert(cc.pointCount > 0);
switch (cc.type)
{
case ManifoldType.Circles:
{
Vector2 pointA = cc.bodyA.GetWorldPoint(cc.localPoint);
Vector2 pointB = cc.bodyB.GetWorldPoint(cc.localPoints[0]);
if ((pointA - pointB).LengthSquared() > Settings.b2_epsilon * Settings.b2_epsilon)
{
normal = pointB - pointA;
normal.Normalize();
}
else
{
normal = new Vector2(1.0f, 0.0f);
}
point = 0.5f * (pointA + pointB);
separation = Vector2.Dot(pointB - pointA, normal) - cc.radius;
}
break;
case ManifoldType.FaceA:
{
normal = cc.bodyA.GetWorldVector(cc.localNormal);
Vector2 planePoint = cc.bodyA.GetWorldPoint(cc.localPoint);
Vector2 clipPoint = cc.bodyB.GetWorldPoint(cc.localPoints[index]);
separation = Vector2.Dot(clipPoint - planePoint, normal) - cc.radius;
point = clipPoint;
}
break;
case ManifoldType.FaceB:
{
normal = cc.bodyB.GetWorldVector(cc.localNormal);
Vector2 planePoint = cc.bodyB.GetWorldPoint(cc.localPoint);
Vector2 clipPoint = cc.bodyA.GetWorldPoint(cc.localPoints[index]);
separation = Vector2.Dot(clipPoint - planePoint, normal) - cc.radius;
point = clipPoint;
// Ensure normal points from A to B
normal = -normal;
}
break;
default:
normal = Vector2.UnitY;
point = Vector2.Zero;
separation = 0.0f;
break;
}
}
public TOISolverManifold(ref TOIConstraint cc, int index)
{
Debug.Assert(cc.pointCount > 0);
switch (cc.type)
{
case ManifoldType.Circles:
{
Vector2 pointA = cc.bodyA.GetWorldPoint(cc.localPoint);
Vector2 pointB = cc.bodyB.GetWorldPoint(cc.localPoints[0]);
if ((pointA - pointB).LengthSquared() > Settings.b2_epsilon * Settings.b2_epsilon)
{
normal = pointB - pointA;
normal.Normalize();
}
else
{
normal = new Vector2(1.0f, 0.0f);
}
point = 0.5f * (pointA + pointB);
separation = Vector2.Dot(pointB - pointA, normal) - cc.radius;
}
break;
case ManifoldType.FaceA:
{
normal = cc.bodyA.GetWorldVector(cc.localNormal);
Vector2 planePoint = cc.bodyA.GetWorldPoint(cc.localPoint);
Vector2 clipPoint = cc.bodyB.GetWorldPoint(cc.localPoints[index]);
separation = Vector2.Dot(clipPoint - planePoint, normal) - cc.radius;
point = clipPoint;
}
break;
case ManifoldType.FaceB:
{
normal = cc.bodyB.GetWorldVector(cc.localNormal);
Vector2 planePoint = cc.bodyB.GetWorldPoint(cc.localPoint);
Vector2 clipPoint = cc.bodyA.GetWorldPoint(cc.localPoints[index]);
separation = Vector2.Dot(clipPoint - planePoint, normal) - cc.radius;
point = clipPoint;
// Ensure normal points from A to B
normal = -normal;
}
break;
default:
normal = Vector2.UnitY;
point = Vector2.Zero;
separation = 0.0f;
break;
}
}
public void Initialize(Contact[] contacts, int count, Body toiBody)
{
_count = count;
_toiBody = toiBody;
if (_constraints.Length < _count)
{
_constraints = new TOIConstraint[Math.Max(_constraints.Length * 2, _count)];
}
for (int i = 0; i < _count; ++i)
{
Contact contact = contacts[i];
Fixture fixtureA = contact.GetFixtureA();
Fixture fixtureB = contact.GetFixtureB();
Shape shapeA = fixtureA.GetShape();
Shape shapeB = fixtureB.GetShape();
float radiusA = shapeA._radius;
float radiusB = shapeB._radius;
Body bodyA = fixtureA.GetBody();
Body bodyB = fixtureB.GetBody();
Manifold manifold;
contact.GetManifold(out manifold);
Debug.Assert(manifold._pointCount > 0);
TOIConstraint constraint = _constraints[i];
constraint.bodyA = bodyA;
constraint.bodyB = bodyB;
constraint.localNormal = manifold._localNormal;
constraint.localPoint = manifold._localPoint;
constraint.type = manifold._type;
constraint.pointCount = manifold._pointCount;
constraint.radius = radiusA + radiusB;
for (int j = 0; j < constraint.pointCount; ++j)
{
constraint.localPoints[j] = manifold._points[j].LocalPoint;
}
_constraints[i] = constraint;
}
}
/// <summary>
/// Perform one solver iteration. Returns true if converged.
/// </summary>
/// <param name="baumgarte"></param>
/// <returns></returns>
public bool Solve(float baumgarte)
{
float minSeparation = 0.0f;
for (int i = 0; i < _count; ++i)
{
TOIConstraint c = _constraints[i];
Body bodyA = c.bodyA;
Body bodyB = c.bodyB;
float massA = bodyA._mass;
float massB = bodyB._mass;
// Only the TOI body should move.
if (bodyA == _toiBody)
{
massB = 0.0f;
}
else
{
massA = 0.0f;
}
float invMassA = massA * bodyA._invMass;
float invIA = massA * bodyA._invI;
float invMassB = massB * bodyB._invMass;
float invIB = massB * bodyB._invI;
// Solve normal constraints
for (int j = 0; j < c.pointCount; ++j)
{
TOISolverManifold psm = new TOISolverManifold(ref c, j);
Vector2 normal = psm.normal;
Vector2 point = psm.point;
float separation = psm.separation;
Vector2 rA = point - bodyA._sweep.c;
Vector2 rB = point - bodyB._sweep.c;
// Track max constraint error.
minSeparation = Math.Min(minSeparation, separation);
// Prevent large corrections and allow slop.
float C = MathUtils.Clamp(baumgarte * (separation + Settings.b2_linearSlop), -Settings.b2_maxLinearCorrection, 0.0f);
// Compute the effective mass.
float rnA = MathUtils.Cross(rA, normal);
float rnB = MathUtils.Cross(rB, normal);
float K = invMassA + invMassB + invIA * rnA * rnA + invIB * rnB * rnB;
// Compute normal impulse
float impulse = K > 0.0f ? -C / K : 0.0f;
Vector2 P = impulse * normal;
bodyA._sweep.c -= invMassA * P;
bodyA._sweep.a -= invIA * MathUtils.Cross(rA, P);
bodyA.SynchronizeTransform();
bodyB._sweep.c += invMassB * P;
bodyB._sweep.a += invIB * MathUtils.Cross(rB, P);
bodyB.SynchronizeTransform();
}
}
// We can't expect minSpeparation >= -b2_linearSlop because we don't
// push the separation above -b2_linearSlop.
return(minSeparation >= -1.5f * Settings.b2_linearSlop);
}