static public b2ContactPositionConstraint Create()
{
var cvc = new b2ContactPositionConstraint();
cvc.Defaults();
return(cvc);
}
public b2PositionSolverManifold(b2ContactPositionConstraint pc, ref b2Transform xfA, ref b2Transform xfB, int index)
{
Debug.Assert(pc.pointCount > 0);
switch (pc.type)
{
case b2ManifoldType.e_circles:
{
b2Vec2 pointA = b2Math.b2Mul(xfA, pc.localPoint);
b2Vec2 pointB = b2Math.b2Mul(xfB, pc.localPoints[0]);
normal = pointB - pointA;
normal.Normalize();
point = 0.5f * (pointA + pointB);
separation = b2Math.b2Dot(pointB - pointA, normal) - pc.radiusA - pc.radiusB;
}
break;
case b2ManifoldType.e_faceA:
{
normal = b2Math.b2Mul(xfA.q, pc.localNormal);
b2Vec2 planePoint = b2Math.b2Mul(xfA, pc.localPoint);
b2Vec2 clipPoint = b2Math.b2Mul(xfB, pc.localPoints[index]);
b2Vec2 rCP = clipPoint - planePoint;
separation = b2Math.b2Dot(ref rCP, ref normal) - pc.radiusA - pc.radiusB;
point = clipPoint;
}
break;
case b2ManifoldType.e_faceB:
{
normal = b2Math.b2Mul(xfB.q, pc.localNormal);
b2Vec2 planePoint = b2Math.b2Mul(xfB, pc.localPoint);
b2Vec2 clipPoint = b2Math.b2Mul(xfA, pc.localPoints[index]);
b2Vec2 rCP = clipPoint - planePoint;
separation = b2Math.b2Dot(ref rCP, ref normal) - pc.radiusA - pc.radiusB;
point = clipPoint;
// Ensure normal points from A to B
normal = -normal;
}
break;
}
}
public b2PositionSolverManifold(ref b2ContactPositionConstraint pc, ref b2Transform xfA, ref b2Transform xfB, int index)
{
Debug.Assert(pc.pointCount > 0);
switch (pc.type)
{
case b2ManifoldType.e_circles:
{
b2Vec2 pointA = b2Math.b2Mul(xfA, pc.localPoint);
b2Vec2 pointB = b2Math.b2Mul(xfB, pc.localPoints[0]);
normal = pointB - pointA;
normal.Normalize();
point = 0.5f * (pointA + pointB);
separation = b2Math.b2Dot(pointB - pointA, normal) - pc.radiusA - pc.radiusB;
}
break;
case b2ManifoldType.e_faceA:
{
normal = b2Math.b2Mul(xfA.q, pc.localNormal);
b2Vec2 planePoint = b2Math.b2Mul(xfA, pc.localPoint);
b2Vec2 clipPoint = b2Math.b2Mul(xfB, pc.localPoints[index]);
separation = b2Math.b2Dot(clipPoint - planePoint, normal) - pc.radiusA - pc.radiusB;
point = clipPoint;
}
break;
case b2ManifoldType.e_faceB:
{
normal = b2Math.b2Mul(xfB.q, pc.localNormal);
b2Vec2 planePoint = b2Math.b2Mul(xfB, pc.localPoint);
b2Vec2 clipPoint = b2Math.b2Mul(xfA, pc.localPoints[index]);
separation = b2Math.b2Dot(clipPoint - planePoint, normal) - pc.radiusA - pc.radiusB;
point = clipPoint;
// Ensure normal points from A to B
normal = -normal;
}
break;
}
}
public static b2ContactPositionConstraint Create()
{
var cvc = new b2ContactPositionConstraint();
cvc.Defaults();
return cvc;
}
// Sequential position solver for position constraints.
public bool SolveTOIPositionConstraints(int toiIndexA, int toiIndexB)
{
float minSeparation = 0.0f;
for (int i = 0; i < m_count; ++i)
{
b2ContactPositionConstraint pc = m_positionConstraints[i];
int indexA = pc.indexA;
int indexB = pc.indexB;
b2Vec2 localCenterA = pc.localCenterA;
b2Vec2 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 = pc.invMassB;
float iB = pc.invIB;
if (indexB == toiIndexA || indexB == toiIndexB)
{
mB = pc.invMassB;
iB = pc.invIB;
}
b2Vec2 cA = m_positions[indexA].c;
float aA = m_positions[indexA].a;
b2Vec2 cB = m_positions[indexB].c;
float aB = m_positions[indexB].a;
// Solve normal constraints
for (int j = 0; j < pointCount; ++j)
{
b2Transform xfA = b2Transform.Identity, xfB = b2Transform.Identity;
xfA.q.Set(aA);
xfB.q.Set(aB);
xfA.p = cA - b2Math.b2Mul(xfA.q, localCenterA);
xfB.p = cB - b2Math.b2Mul(xfB.q, localCenterB);
b2PositionSolverManifold psm = new b2PositionSolverManifold(pc, ref xfA, ref xfB, j);
b2Vec2 normal = psm.normal;
b2Vec2 point = psm.point;
float separation = psm.separation;
b2Vec2 rA = point - cA;
b2Vec2 rB = point - cB;
// Track max constraint error.
minSeparation = Math.Min(minSeparation, separation);
// Prevent large corrections and allow slop.
float C = b2Math.b2Clamp(b2Settings.b2_toiBaugarte * (separation + b2Settings.b2_linearSlop), -b2Settings.b2_maxLinearCorrection, 0.0f);
// Compute the effective mass.
float rnA = b2Math.b2Cross(ref rA, ref normal);
float rnB = b2Math.b2Cross(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;
b2Vec2 P = impulse * normal;
cA -= mA * P;
aA -= iA * b2Math.b2Cross(rA, P);
cB += mB * P;
aB += iB * b2Math.b2Cross(rB, P);
}
m_positions[indexA].c = cA;
m_positions[indexA].a = aA;
m_positions[indexB].c = cB;
m_positions[indexB].a = aB;
//m_positionConstraints[i] = pc;
}
// We can't expect minSpeparation >= -b2_linearSlop because we don't
// push the separation above -b2_linearSlop.
return(minSeparation >= -1.5f * b2Settings.b2_linearSlop);
}
// Initialize position dependent portions of the velocity constraints.
public virtual void InitializeVelocityConstraints()
{
for (int i = 0; i < m_count; ++i)
{
b2ContactVelocityConstraint vc = m_velocityConstraints[i];
b2ContactPositionConstraint pc = m_positionConstraints[i];
float radiusA = pc.radiusA;
float radiusB = pc.radiusB;
b2Manifold manifold = m_contacts[vc.contactIndex].GetManifold();
int indexA = vc.indexA;
int indexB = vc.indexB;
float mA = vc.invMassA;
float mB = vc.invMassB;
float iA = vc.invIA;
float iB = vc.invIB;
b2Vec2 localCenterA = pc.localCenterA;
b2Vec2 localCenterB = pc.localCenterB;
b2Vec2 cA = m_positions[indexA].c;
float aA = m_positions[indexA].a;
b2Vec2 vA = m_velocities[indexA].v;
float wA = m_velocities[indexA].w;
b2Vec2 cB = m_positions[indexB].c;
float aB = m_positions[indexB].a;
b2Vec2 vB = m_velocities[indexB].v;
float wB = m_velocities[indexB].w;
Debug.Assert(manifold.pointCount > 0);
b2Transform xfA = b2Transform.Identity, xfB = b2Transform.Identity;
xfA.q.Set(aA);
xfB.q.Set(aB);
xfA.p = cA - b2Math.b2Mul(ref xfA.q, ref localCenterA);
xfB.p = cB - b2Math.b2Mul(ref xfB.q, ref localCenterB);
b2WorldManifold worldManifold = new b2WorldManifold();
worldManifold.Initialize(ref manifold, xfA, radiusA, xfB, radiusB);
vc.normal = worldManifold.normal;
int pointCount = vc.pointCount;
for (int j = 0; j < pointCount; ++j)
{
b2VelocityConstraintPoint vcp = vc.points[j];
vcp.rA = worldManifold.points[j] - cA;
vcp.rB = worldManifold.points[j] - cB;
float rnA = b2Math.b2Cross(ref vcp.rA, ref vc.normal);
float rnB = b2Math.b2Cross(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;
b2Vec2 tangent = vc.normal.UnitCross(); // b2Math.b2Cross(vc.normal, 1.0f);
float rtA = b2Math.b2Cross(ref vcp.rA, ref tangent);
float rtB = b2Math.b2Cross(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 = b2Math.b2Dot(vc.normal, vB + b2Math.b2Cross(wB, ref vcp.rB) - vA - b2Math.b2Cross(wA, ref vcp.rA));
if (vRel < -b2Settings.b2_velocityThreshold)
{
vcp.velocityBias = -vc.restitution * vRel;
}
//vc.points[j] = vcp;
}
// If we have two points, then prepare the block solver.
if (vc.pointCount == 2)
{
b2VelocityConstraintPoint vcp1 = vc.points[0];
b2VelocityConstraintPoint vcp2 = vc.points[1];
float rn1A = b2Math.b2Cross(ref vcp1.rA, ref vc.normal);
float rn1B = b2Math.b2Cross(ref vcp1.rB, ref vc.normal);
float rn2A = b2Math.b2Cross(ref vcp2.rA, ref vc.normal);
float rn2B = b2Math.b2Cross(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.
float k_maxConditionNumber = 1000.0f;
if (k11 * k11 < k_maxConditionNumber * (k11 * k22 - k12 * k12))
{
// K is safe to invert.
vc.K.ex.Set(k11, k12);
vc.K.ey.Set(k12, k22);
vc.normalMass = vc.K.GetInverse();
}
else
{
// The constraints are redundant, just use one.
// TODO_ERIN use deepest?
vc.pointCount = 1;
}
}
//m_positionConstraints[i] = pc;
//m_velocityConstraints[i] = vc;
}
}
public b2ContactSolver(b2ContactSolverDef def)
{
m_step = def.step;
m_count = def.count;
m_positionConstraints = new b2ContactPositionConstraint[m_count];
for (int pc = 0; pc < m_count; pc++)
{
m_positionConstraints[pc] = b2ContactPositionConstraint.Create();
}
m_velocityConstraints = new b2ContactVelocityConstraint[m_count];
for (int vc = 0; vc < m_count; vc++)
{
m_velocityConstraints[vc] = b2ContactVelocityConstraint.Create();
}
m_positions = def.positions;
m_velocities = def.velocities;
m_contacts = def.contacts;
// Initialize position independent portions of the constraints.
for (int i = 0; i < m_count; ++i)
{
b2Contact contact = m_contacts[i];
b2Fixture fixtureA = contact.FixtureA;
b2Fixture fixtureB = contact.FixtureB;
b2Shape shapeA = fixtureA.Shape;
b2Shape shapeB = fixtureB.Shape;
float radiusA = shapeA.Radius;
float radiusB = shapeB.Radius;
b2Body bodyA = fixtureA.Body;
b2Body bodyB = fixtureB.Body;
b2Manifold manifold = contact.GetManifold();
int pointCount = manifold.pointCount;
Debug.Assert(pointCount > 0);
b2ContactVelocityConstraint vc = m_velocityConstraints[i];
vc.friction = contact.Friction;
vc.restitution = contact.Restitution;
vc.indexA = bodyA.IslandIndex;
vc.indexB = bodyB.IslandIndex;
vc.invMassA = bodyA.InvertedMass;
vc.invMassB = bodyB.InvertedMass;
vc.invIA = bodyA.InvertedI;
vc.invIB = bodyB.InvertedI;
vc.contactIndex = i;
vc.pointCount = pointCount;
vc.K.SetZero();
vc.normalMass.SetZero();
b2ContactPositionConstraint pc = m_positionConstraints[i];
pc.indexA = bodyA.IslandIndex;
pc.indexB = bodyB.IslandIndex;
pc.invMassA = bodyA.InvertedMass;
pc.invMassB = bodyB.InvertedMass;
pc.localCenterA = bodyA.Sweep.localCenter;
pc.localCenterB = bodyB.Sweep.localCenter;
pc.invIA = bodyA.InvertedI;
pc.invIB = bodyB.InvertedI;
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)
{
b2ManifoldPoint cp = manifold.points[j];
b2VelocityConstraintPoint vcp = vc.points[j];
if (m_step.warmStarting)
{
vcp.normalImpulse = m_step.dtRatio * cp.normalImpulse;
vcp.tangentImpulse = m_step.dtRatio * cp.tangentImpulse;
}
else
{
vcp.normalImpulse = 0.0f;
vcp.tangentImpulse = 0.0f;
}
vcp.rA.SetZero();
vcp.rB.SetZero();
vcp.normalMass = 0.0f;
vcp.tangentMass = 0.0f;
vcp.velocityBias = 0.0f;
pc.localPoints[j] = cp.localPoint;
//vc.points[j] = vcp;
}
//Put back the struct data since struct data is copied by value
//m_positionConstraints[i] = pc;
//m_velocityConstraints[i] = vc;
}
}