public ContactSolver(ContactSolverDef def)
{
_step = def.step;
_count = def.count;
_positionConstraints = new ContactPositionConstraint[_count];
_velocityConstraints = new ContactVelocityConstraint[_count];
_positions = def.positions;
_velocities = def.velocities;
_contacts = def.contacts;
for (int i = 0; i < _count; ++i)
{
Contact contact = _contacts[i];
Fixture fixtureA = contact.m_fixtureA;
Fixture fixtureB = contact.m_fixtureB;
Shape shapeA = fixtureA.Shape;
Shape shapeB = fixtureB.Shape;
float radiusA = shapeA.m_radius;
float radiusB = shapeB.m_radius;
Body bodyA = fixtureA.Body;
Body bodyB = fixtureB.Body;
Manifold manifold = contact.Manifold;
int pointCount = manifold.pointCount;
//Debug.Assert(pointCount > 0);
_velocityConstraints[i] = new ContactVelocityConstraint();
ContactVelocityConstraint vc = _velocityConstraints[i];
vc.friction = contact.m_friction;
vc.restitution = contact.m_restitution;
vc.tangentSpeed = contact.m_tangentSpeed;
vc.indexA = bodyA.m_islandIndex;
vc.indexB = bodyB.m_islandIndex;
vc.invMassA = bodyA.m_invMass;
vc.invMassB = bodyB.m_invMass;
vc.invIA = bodyA.m_invI;
vc.invIB = bodyB.m_invI;
vc.contactIndex = i;
vc.pointCount = pointCount;
vc.K = new Matrix3x2(); // .SetZero();
vc.normalMass = new Matrix3x2(); // .SetZero();
_positionConstraints[i] = new ContactPositionConstraint();
ContactPositionConstraint pc = _positionConstraints[i];
pc.indexA = bodyA.m_islandIndex;
pc.indexB = bodyB.m_islandIndex;
pc.invMassA = bodyA.m_invMass;
pc.invMassB = bodyB.m_invMass;
pc.localCenterA = bodyA.m_sweep.localCenter;
pc.localCenterB = bodyB.m_sweep.localCenter;
pc.invIA = bodyA.m_invI;
pc.invIB = bodyB.m_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];
vc.points[j] = new VelocityConstraintPoint();
VelocityConstraintPoint vcp = vc.points[j];
if (_step.warmStarting)
{
vcp.normalImpulse = _step.dtRatio * cp.normalImpulse;
vcp.tangentImpulse = _step.dtRatio * cp.tangentImpulse;
}
else
{
vcp.normalImpulse = 0f;
vcp.tangentImpulse = 0f;
}
vcp.rA = Vector2.Zero;
vcp.rB = Vector2.Zero;
vcp.normalMass = 0f;
vcp.tangentMass = 0f;
vcp.velocityBias = 0f;
pc.localPoints[j] = cp.localPoint;
}
}
}
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();
Transform xfB = new Transform();
xfA.q = Matrex.CreateRotation(aA); // Actually about twice as fast to use our own function
xfB.q = Matrex.CreateRotation(aB); // Actually about twice as fast to use our own function
xfA.p = cA - Vector2.Transform(localCenterA, xfA.q); // Common.Math.Mul(xfA.q, localCenterA);
xfB.p = cB - Vector2.Transform(localCenterB, xfB.q); // Common.Math.Mul(xfB.q, localCenterB);
PositionSolverManifold psm = new PositionSolverManifold();
psm.Initialize(pc, xfA, xfB, j);
Vector2 normal = psm.normal;
Vector2 point = psm.point;
float separation = psm.separation;
Vector2 rA = point - cA;
Vector2 rB = point - cB;
// Track max constraint error.
minSeparation = MathF.Min(minSeparation, separation);
// Prevent large corrections and allow slop.
float C = Math.Clamp(Settings.TOIBaumgarte * (separation + Settings.LinearSlop),
-Settings.MaxLinearCorrection, 0.0f);
// Compute the effective mass.
float rnA = Vectex.Cross(rA, normal);
float rnB = Vectex.Cross(rB, 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 * Vectex.Cross(rA, P);
cB += mB * P;
aB += iB * Vectex.Cross(rB, 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);
}
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();
Transform xfB = new Transform();
xfA.q = Matrex.CreateRotation(aA); // Actually about twice as fast to use our own function
xfB.q = Matrex.CreateRotation(aB); // Actually about twice as fast to use our own function
xfA.p = cA - Vector2.Transform(localCenterA, xfA.q); // Common.Math.Mul(xfA.q, localCenterA);
xfB.p = cB - Vector2.Transform(localCenterB, xfB.q); // Common.Math.Mul(xfB.q, localCenterB);
WorldManifold worldManifold = new WorldManifold();
worldManifold.Initialize(manifold, xfA, radiusA, xfB, radiusB);
vc.normal = worldManifold.normal;
int pointCount = vc.pointCount;
for (int j = 0; j < pointCount; ++j)
{
VelocityConstraintPoint vcp = vc.points[j];
vcp.rA = worldManifold.points[j] - cA;
vcp.rB = worldManifold.points[j] - cB;
float rnA = Vectex.Cross(vcp.rA, vc.normal);
float rnB = Vectex.Cross(vcp.rB, vc.normal);
float kNormal = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
vcp.normalMass = kNormal > 0f ? 1f / kNormal : 0f;
Vector2 tangent = Vectex.Cross(vc.normal, 1f);
float rtA = Vectex.Cross(vcp.rA, tangent);
float rtB = Vectex.Cross(vcp.rB, tangent);
float kTangent = mA + mB + iA * rtA * rtA + iB * rtB * rtB;
vcp.tangentMass = kTangent > 0f ? 1f / kTangent : 0f;
vcp.velocityBias = 0f;
float vRel = Vector2.Dot(vc.normal, vB + Vectex.Cross(wB, vcp.rB) - vA - Vectex.Cross(wA, 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 && Settings.BlockSolve)
{
VelocityConstraintPoint vcp1 = vc.points[0];
VelocityConstraintPoint vcp2 = vc.points[1];
float rn1A = Vectex.Cross(vcp1.rA, vc.normal);
float rn1B = Vectex.Cross(vcp1.rB, vc.normal);
float rn2A = Vectex.Cross(vcp2.rA, vc.normal);
float rn2B = Vectex.Cross(vcp2.rB, 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 = new Matrix3x2(k11, k12, k12, k22, 0, 0);
// vc.K.ex = new Vector2(k11, k12);
// vc.K.ey = new Vector2(k12, k22);
/*Matrix3x2*/
Matrex.Invert(vc.K, out Matrix3x2 KT);
vc.normalMass = KT;
}
else
{
// The constraints are redundant, just use one.
// TODO_ERIN use deepest?
vc.pointCount = 1;
}
}
}
}