// Sequential position solver for position constraints.
public bool SolveTOIPositionConstraints(int toiIndexA, int toiIndexB)
{
float minSeparation = 0.0f;
for (int i = 0; i < _count; ++i)
{
ContactPositionConstraint pc = _positionConstraints[i];
int indexA = pc.indexA;
int indexB = pc.indexB;
Vector2 localCenterA = pc.localCenterA;
Vector2 localCenterB = pc.localCenterB;
int pointCount = pc.pointCount;
float mA = 0.0f;
float iA = 0.0f;
if (indexA == toiIndexA || indexA == toiIndexB)
{
mA = pc.invMassA;
iA = pc.invIA;
}
float mB = 0.0f;
float iB = 0.0f;
if (indexB == toiIndexA || indexB == toiIndexB)
{
mB = pc.invMassB;
iB = pc.invIB;
}
Vector2 cA = _positions[indexA].c;
float aA = _positions[indexA].a;
Vector2 cB = _positions[indexB].c;
float aB = _positions[indexB].a;
// Solve normal constraints
for (int j = 0; j < pointCount; ++j)
{
Transform xfA = new Transform(Vector2.Zero, aA);
Transform xfB = new Transform(Vector2.Zero, aB);
xfA.p = cA - Complex.Multiply(ref localCenterA, ref xfA.q);
xfB.p = cB - Complex.Multiply(ref localCenterB, ref xfB.q);
Vector2 normal;
Vector2 point;
float separation;
PositionSolverManifold.Initialize(pc, ref xfA, ref xfB, j, out normal, out point, out separation);
Vector2 rA = point - cA;
Vector2 rB = point - cB;
// Track max constraint error.
minSeparation = Math.Min(minSeparation, separation);
// Prevent large corrections and allow slop.
float C = MathUtils.Clamp(Settings.Baumgarte * (separation + Settings.LinearSlop), -Settings.MaxLinearCorrection, 0.0f);
// Compute the effective mass.
float rnA = MathUtils.Cross(ref rA, ref normal);
float rnB = MathUtils.Cross(ref rB, ref normal);
float K = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
// Compute normal impulse
float impulse = K > 0.0f ? -C / K : 0.0f;
Vector2 P = impulse * normal;
cA -= mA * P;
aA -= iA * MathUtils.Cross(ref rA, ref P);
cB += mB * P;
aB += iB * MathUtils.Cross(ref rB, ref P);
}
_positions[indexA].c = cA;
_positions[indexA].a = aA;
_positions[indexB].c = cB;
_positions[indexB].a = aB;
}
// We can't expect minSpeparation >= -b2_linearSlop because we don't
// push the separation above -b2_linearSlop.
return(minSeparation >= -1.5f * Settings.LinearSlop);
}
private bool SolvePositionConstraints(int start, int end)
{
float minSeparation = 0.0f;
for (int i = start; i < end; ++i)
{
ContactPositionConstraint pc = _positionConstraints[i];
#if NET40 || NET45 || NETSTANDARD2_0 || PORTABLE40 || PORTABLE45 || W10 || W8_1 || WP8_1
// Find lower order item.
int orderedIndexA = pc.indexA;
int orderedIndexB = pc.indexB;
if (orderedIndexB < orderedIndexA)
{
orderedIndexA = pc.indexB;
orderedIndexB = pc.indexA;
}
// Lock bodies.
for (; ;)
{
if (Interlocked.CompareExchange(ref _locks[orderedIndexA], 1, 0) == 0)
{
if (Interlocked.CompareExchange(ref _locks[orderedIndexB], 1, 0) == 0)
{
break;
}
System.Threading.Interlocked.Exchange(ref _locks[orderedIndexA], 0);
}
#if NET40 || NET45 || NETSTANDARD2_0
Thread.Sleep(0);
#endif
}
#endif
int indexA = pc.indexA;
int indexB = pc.indexB;
Vector2 localCenterA = pc.localCenterA;
float mA = pc.invMassA;
float iA = pc.invIA;
Vector2 localCenterB = pc.localCenterB;
float mB = pc.invMassB;
float iB = pc.invIB;
int pointCount = pc.pointCount;
Vector2 cA = _positions[indexA].c;
float aA = _positions[indexA].a;
Vector2 cB = _positions[indexB].c;
float aB = _positions[indexB].a;
// Solve normal constraints
for (int j = 0; j < pointCount; ++j)
{
Transform xfA = new Transform(Vector2.Zero, aA);
Transform xfB = new Transform(Vector2.Zero, aB);
xfA.p = cA - Complex.Multiply(ref localCenterA, ref xfA.q);
xfB.p = cB - Complex.Multiply(ref localCenterB, ref xfB.q);
Vector2 normal;
Vector2 point;
float separation;
PositionSolverManifold.Initialize(pc, ref xfA, ref xfB, j, out normal, out point, out separation);
Vector2 rA = point - cA;
Vector2 rB = point - cB;
// Track max constraint error.
minSeparation = Math.Min(minSeparation, separation);
// Prevent large corrections and allow slop.
float C = MathUtils.Clamp(Settings.Baumgarte * (separation + Settings.LinearSlop), -Settings.MaxLinearCorrection, 0.0f);
// Compute the effective mass.
float rnA = MathUtils.Cross(ref rA, ref normal);
float rnB = MathUtils.Cross(ref rB, ref normal);
float K = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
// Compute normal impulse
float impulse = K > 0.0f ? -C / K : 0.0f;
Vector2 P = impulse * normal;
cA -= mA * P;
aA -= iA * MathUtils.Cross(ref rA, ref P);
cB += mB * P;
aB += iB * MathUtils.Cross(ref rB, ref P);
}
_positions[indexA].c = cA;
_positions[indexA].a = aA;
_positions[indexB].c = cB;
_positions[indexB].a = aB;
#if NET40 || NET45 || NETSTANDARD2_0 || PORTABLE40 || PORTABLE45 || W10 || W8_1 || WP8_1
// Unlock bodies.
System.Threading.Interlocked.Exchange(ref _locks[orderedIndexB], 0);
System.Threading.Interlocked.Exchange(ref _locks[orderedIndexA], 0);
#endif
}
// We can't expect minSpeparation >= -b2_linearSlop because we don't
// push the separation above -b2_linearSlop.
return(minSeparation >= -3.0f * Settings.LinearSlop);
}
internal void Reset(ref TimeStep step, int count, Contact[] contacts, SolverPosition[] positions, SolverVelocity[] velocities,
int[] locks, int velocityConstraintsMultithreadThreshold, int positionConstraintsMultithreadThreshold)
{
_count = count;
_positions = positions;
_velocities = velocities;
_locks = locks;
_contacts = contacts;
_velocityConstraintsMultithreadThreshold = velocityConstraintsMultithreadThreshold;
_positionConstraintsMultithreadThreshold = positionConstraintsMultithreadThreshold;
// grow the array
if (_velocityConstraints == null || _velocityConstraints.Length < count)
{
int newBufferCount = Math.Max(count, 32);
newBufferCount = newBufferCount + (newBufferCount * 2 >> 4); // grow by x1.125f
newBufferCount = (newBufferCount + 31) & (~31); // grow in chunks of 32.
int oldBufferCount = (_velocityConstraints == null) ? 0 : _velocityConstraints.Length;
Array.Resize(ref _velocityConstraints, newBufferCount);
Array.Resize(ref _positionConstraints, newBufferCount);
for (int i = oldBufferCount; i < newBufferCount; i++)
{
_velocityConstraints[i] = new ContactVelocityConstraint();
_positionConstraints[i] = new ContactPositionConstraint();
}
}
// Initialize position independent portions of the constraints.
for (int i = 0; i < _count; ++i)
{
Contact contact = contacts[i];
Fixture fixtureA = contact.FixtureA;
Fixture fixtureB = contact.FixtureB;
Shape shapeA = fixtureA.Shape;
Shape shapeB = fixtureB.Shape;
float radiusA = shapeA.Radius;
float radiusB = shapeB.Radius;
Body bodyA = fixtureA.Body;
Body bodyB = fixtureB.Body;
Manifold manifold = contact.Manifold;
int pointCount = manifold.PointCount;
Debug.Assert(pointCount > 0);
ContactVelocityConstraint vc = _velocityConstraints[i];
vc.friction = contact.Friction;
vc.restitution = contact.Restitution;
vc.tangentSpeed = contact.TangentSpeed;
vc.indexA = bodyA.IslandIndex;
vc.indexB = bodyB.IslandIndex;
vc.invMassA = bodyA._invMass;
vc.invMassB = bodyB._invMass;
vc.invIA = bodyA._invI;
vc.invIB = bodyB._invI;
vc.contactIndex = i;
vc.pointCount = pointCount;
vc.K.SetZero();
vc.normalMass.SetZero();
ContactPositionConstraint pc = _positionConstraints[i];
pc.indexA = bodyA.IslandIndex;
pc.indexB = bodyB.IslandIndex;
pc.invMassA = bodyA._invMass;
pc.invMassB = bodyB._invMass;
pc.localCenterA = bodyA._sweep.LocalCenter;
pc.localCenterB = bodyB._sweep.LocalCenter;
pc.invIA = bodyA._invI;
pc.invIB = bodyB._invI;
pc.localNormal = manifold.LocalNormal;
pc.localPoint = manifold.LocalPoint;
pc.pointCount = pointCount;
pc.radiusA = radiusA;
pc.radiusB = radiusB;
pc.type = manifold.Type;
for (int j = 0; j < pointCount; ++j)
{
ManifoldPoint cp = manifold.Points[j];
VelocityConstraintPoint vcp = vc.points[j];
if (step.warmStarting)
{
vcp.normalImpulse = step.dtRatio * cp.NormalImpulse;
vcp.tangentImpulse = step.dtRatio * cp.TangentImpulse;
}
else
{
vcp.normalImpulse = 0.0f;
vcp.tangentImpulse = 0.0f;
}
vcp.rA = Vector2.Zero;
vcp.rB = Vector2.Zero;
vcp.normalMass = 0.0f;
vcp.tangentMass = 0.0f;
vcp.velocityBias = 0.0f;
pc.localPoints[j] = cp.LocalPoint;
}
}
}
public void InitializeVelocityConstraints()
{
for (int i = 0; i < _count; ++i)
{
ContactVelocityConstraint vc = _velocityConstraints[i];
ContactPositionConstraint pc = _positionConstraints[i];
float radiusA = pc.radiusA;
float radiusB = pc.radiusB;
Manifold manifold = _contacts[vc.contactIndex].Manifold;
int indexA = vc.indexA;
int indexB = vc.indexB;
float mA = vc.invMassA;
float mB = vc.invMassB;
float iA = vc.invIA;
float iB = vc.invIB;
Vector2 localCenterA = pc.localCenterA;
Vector2 localCenterB = pc.localCenterB;
Vector2 cA = _positions[indexA].c;
float aA = _positions[indexA].a;
Vector2 vA = _velocities[indexA].v;
float wA = _velocities[indexA].w;
Vector2 cB = _positions[indexB].c;
float aB = _positions[indexB].a;
Vector2 vB = _velocities[indexB].v;
float wB = _velocities[indexB].w;
Debug.Assert(manifold.PointCount > 0);
Transform xfA = new Transform(Vector2.Zero, aA);
Transform xfB = new Transform(Vector2.Zero, aB);
xfA.p = cA - Complex.Multiply(ref localCenterA, ref xfA.q);
xfB.p = cB - Complex.Multiply(ref localCenterB, ref xfB.q);
Vector2 normal;
FixedArray2 <Vector2> points;
WorldManifold.Initialize(ref manifold, ref xfA, radiusA, ref xfB, radiusB, out normal, out points);
vc.normal = normal;
Vector2 tangent = MathUtils.Rot270(ref vc.normal);
int pointCount = vc.pointCount;
for (int j = 0; j < pointCount; ++j)
{
VelocityConstraintPoint vcp = vc.points[j];
vcp.rA = points[j] - cA;
vcp.rB = points[j] - cB;
float rnA = MathUtils.Cross(ref vcp.rA, ref vc.normal);
float rnB = MathUtils.Cross(ref vcp.rB, ref vc.normal);
float kNormal = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
vcp.normalMass = kNormal > 0.0f ? 1.0f / kNormal : 0.0f;
float rtA = MathUtils.Cross(ref vcp.rA, ref tangent);
float rtB = MathUtils.Cross(ref vcp.rB, ref tangent);
float kTangent = mA + mB + iA * rtA * rtA + iB * rtB * rtB;
vcp.tangentMass = kTangent > 0.0f ? 1.0f / kTangent : 0.0f;
// Setup a velocity bias for restitution.
vcp.velocityBias = 0.0f;
float vRel = Vector2.Dot(vc.normal, vB + MathUtils.Cross(wB, ref vcp.rB) - vA - MathUtils.Cross(wA, ref vcp.rA));
if (vRel < -Settings.VelocityThreshold)
{
vcp.velocityBias = -vc.restitution * vRel;
}
}
// If we have two points, then prepare the block solver.
if (vc.pointCount == 2)
{
VelocityConstraintPoint vcp1 = vc.points[0];
VelocityConstraintPoint vcp2 = vc.points[1];
float rn1A = MathUtils.Cross(ref vcp1.rA, ref vc.normal);
float rn1B = MathUtils.Cross(ref vcp1.rB, ref vc.normal);
float rn2A = MathUtils.Cross(ref vcp2.rA, ref vc.normal);
float rn2B = MathUtils.Cross(ref vcp2.rB, ref vc.normal);
float k11 = mA + mB + iA * rn1A * rn1A + iB * rn1B * rn1B;
float k22 = mA + mB + iA * rn2A * rn2A + iB * rn2B * rn2B;
float k12 = mA + mB + iA * rn1A * rn2A + iB * rn1B * rn2B;
// Ensure a reasonable condition number.
const float k_maxConditionNumber = 1000.0f;
if (k11 * k11 < k_maxConditionNumber * (k11 * k22 - k12 * k12))
{
// K is safe to invert.
vc.K.ex = new Vector2(k11, k12);
vc.K.ey = new Vector2(k12, k22);
vc.normalMass = vc.K.Inverse;
}
else
{
// The constraints are redundant, just use one.
// TODO_ERIN use deepest?
vc.pointCount = 1;
}
}
}
}
public void Reset(ref TimeStep step, int count, Contact[] contacts, Position[] positions, Velocity[] velocities,
int velocityConstraintsMultithreadThreshold, int positionConstraintsMultithreadThreshold)
{
_count = count;
_positions = positions;
_velocities = velocities;
_contacts = contacts;
_velocityConstraintsMultithreadThreshold = velocityConstraintsMultithreadThreshold;
_positionConstraintsMultithreadThreshold = positionConstraintsMultithreadThreshold;
// grow the array
if (_velocityConstraints == null || _velocityConstraints.Length < count)
{
_velocityConstraints = new ContactVelocityConstraint[count * 2];
_positionConstraints = new ContactPositionConstraint[count * 2];
for (int i = 0; i < _velocityConstraints.Length; i++)
{
_velocityConstraints[i] = new ContactVelocityConstraint();
}
for (int i = 0; i < _positionConstraints.Length; i++)
{
_positionConstraints[i] = new ContactPositionConstraint();
}
}
// Initialize position independent portions of the constraints.
for (int i = 0; i < _count; ++i)
{
Contact contact = contacts[i];
// Contact may have been destroyed during collision handling.
if (contact.FixtureA == null || contact.FixtureB == null)
{
Debug.Assert(contact.FixtureA == null && contact.FixtureB == null);
_count--;
Array.Copy(contacts, i + 1, contacts, i, _count - i);
i--;
continue;
}
Fixture fixtureA = contact.FixtureA;
Fixture fixtureB = contact.FixtureB;
Shape shapeA = fixtureA.Shape;
Shape shapeB = fixtureB.Shape;
float radiusA = shapeA.Radius;
float radiusB = shapeB.Radius;
Body bodyA = fixtureA.Body;
Body bodyB = fixtureB.Body;
Manifold manifold = contact.Manifold;
int pointCount = manifold.PointCount;
Debug.Assert(pointCount > 0);
ContactVelocityConstraint vc = _velocityConstraints[i];
vc.friction = contact.Friction;
vc.restitution = contact.Restitution;
vc.tangentSpeed = contact.TangentSpeed;
vc.indexA = bodyA.IslandIndex;
vc.indexB = bodyB.IslandIndex;
vc.invMassA = bodyA._invMass;
vc.invMassB = bodyB._invMass;
vc.invIA = bodyA._invI;
vc.invIB = bodyB._invI;
vc.contactIndex = i;
vc.pointCount = pointCount;
vc.K.SetZero();
vc.normalMass.SetZero();
ContactPositionConstraint pc = _positionConstraints[i];
pc.indexA = bodyA.IslandIndex;
pc.indexB = bodyB.IslandIndex;
pc.invMassA = bodyA._invMass;
pc.invMassB = bodyB._invMass;
pc.localCenterA = bodyA._sweep.LocalCenter;
pc.localCenterB = bodyB._sweep.LocalCenter;
pc.invIA = bodyA._invI;
pc.invIB = bodyB._invI;
pc.localNormal = manifold.LocalNormal;
pc.localPoint = manifold.LocalPoint;
pc.pointCount = pointCount;
pc.radiusA = radiusA;
pc.radiusB = radiusB;
pc.type = manifold.Type;
for (int j = 0; j < pointCount; ++j)
{
ManifoldPoint cp = manifold.Points[j];
VelocityConstraintPoint vcp = vc.points[j];
if (step.warmStarting)
{
vcp.normalImpulse = step.dtRatio * cp.NormalImpulse;
vcp.tangentImpulse = step.dtRatio * cp.TangentImpulse;
}
else
{
vcp.normalImpulse = 0.0f;
vcp.tangentImpulse = 0.0f;
}
vcp.rA = Vector2.Zero;
vcp.rB = Vector2.Zero;
vcp.normalMass = 0.0f;
vcp.tangentMass = 0.0f;
vcp.velocityBias = 0.0f;
pc.localPoints[j] = cp.LocalPoint;
}
}
}