public void WarmStart()
{
// Warm start.
for (int i = 0; i < _constraintCount; ++i)
{
ContactConstraint c = _constraints[i];
Body bodyA = c.bodyA;
Body bodyB = c.bodyB;
float invMassA = bodyA._invMass;
float invIA = bodyA._invI;
float invMassB = bodyB._invMass;
float invIB = bodyB._invI;
Vector2 normal = c.normal;
#if MATH_OVERLOADS
Vector2 tangent = MathUtils.Cross(normal, 1.0f);
#else
Vector2 tangent = new Vector2(normal.Y, -normal.X);
#endif
for (int j = 0; j < c.pointCount; ++j)
{
ContactConstraintPoint ccp = c.points[j];
#if MATH_OVERLOADS
Vector2 P = ccp.normalImpulse * normal + ccp.tangentImpulse * tangent;
bodyA._angularVelocity -= invIA * MathUtils.Cross(ccp.rA, P);
bodyA._linearVelocity -= invMassA * P;
bodyB._angularVelocity += invIB * MathUtils.Cross(ccp.rB, P);
bodyB._linearVelocity += invMassB * P;
#else
Vector2 P = new Vector2(ccp.normalImpulse * normal.X + ccp.tangentImpulse * tangent.X,
ccp.normalImpulse * normal.Y + ccp.tangentImpulse * tangent.Y);
bodyA._angularVelocity -= invIA * (ccp.rA.X * P.Y - ccp.rA.Y * P.X);
bodyA._linearVelocity.X -= invMassA * P.X;
bodyA._linearVelocity.Y -= invMassA * P.Y;
bodyB._angularVelocity += invIB * (ccp.rB.X * P.Y - ccp.rB.Y * P.X);
bodyB._linearVelocity.X += invMassB * P.X;
bodyB._linearVelocity.Y += invMassB * P.Y;
#endif
c.points[j] = ccp;
}
_constraints[i] = c;
}
}
public void Reset(Contact[] contacts, int contactCount, float impulseRatio)
{
_contacts = contacts;
_constraintCount = contactCount;
// grow the array
if (_constraints == null || _constraints.Length < _constraintCount)
{
_constraints = new ContactConstraint[_constraintCount * 2];
}
for (int i = 0; i < _constraintCount; ++i)
{
Contact contact = contacts[i];
Fixture fixtureA = contact._fixtureA;
Fixture fixtureB = contact._fixtureB;
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);
float friction = Settings.b2MixFriction(fixtureA.GetFriction(), fixtureB.GetFriction());
float restitution = Settings.b2MixRestitution(fixtureA.GetRestitution(), fixtureB.GetRestitution());
Vector2 vA = bodyA._linearVelocity;
Vector2 vB = bodyB._linearVelocity;
float wA = bodyA._angularVelocity;
float wB = bodyB._angularVelocity;
Debug.Assert(manifold._pointCount > 0);
WorldManifold worldManifold = new WorldManifold(ref manifold, ref bodyA._xf, radiusA, ref bodyB._xf, radiusB);
ContactConstraint cc = _constraints[i];
cc.bodyA = bodyA;
cc.bodyB = bodyB;
cc.manifold = manifold;
cc.normal = worldManifold._normal;
cc.pointCount = manifold._pointCount;
cc.friction = friction;
cc.localNormal = manifold._localNormal;
cc.localPoint = manifold._localPoint;
cc.radius = radiusA + radiusB;
cc.type = manifold._type;
for (int j = 0; j < cc.pointCount; ++j)
{
ManifoldPoint cp = manifold._points[j];
ContactConstraintPoint ccp = cc.points[j];
ccp.normalImpulse = impulseRatio * cp.NormalImpulse;
ccp.tangentImpulse = impulseRatio * cp.TangentImpulse;
ccp.localPoint = cp.LocalPoint;
ccp.rA = worldManifold._points[j] - bodyA._sweep.c;
ccp.rB = worldManifold._points[j] - bodyB._sweep.c;
#if MATH_OVERLOADS
float rnA = MathUtils.Cross(ccp.rA, cc.normal);
float rnB = MathUtils.Cross(ccp.rB, cc.normal);
#else
float rnA = ccp.rA.X * cc.normal.Y - ccp.rA.Y * cc.normal.X;
float rnB = ccp.rB.X * cc.normal.Y - ccp.rB.Y * cc.normal.X;
#endif
rnA *= rnA;
rnB *= rnB;
float kNormal = bodyA._invMass + bodyB._invMass + bodyA._invI * rnA + bodyB._invI * rnB;
Debug.Assert(kNormal > Settings.b2_epsilon);
ccp.normalMass = 1.0f / kNormal;
#if MATH_OVERLOADS
Vector2 tangent = MathUtils.Cross(cc.normal, 1.0f);
float rtA = MathUtils.Cross(ccp.rA, tangent);
float rtB = MathUtils.Cross(ccp.rB, tangent);
#else
Vector2 tangent = new Vector2(cc.normal.Y, -cc.normal.X);
float rtA = ccp.rA.X * tangent.Y - ccp.rA.Y * tangent.X;
float rtB = ccp.rB.X * tangent.Y - ccp.rB.Y * tangent.X;
#endif
rtA *= rtA;
rtB *= rtB;
float kTangent = bodyA._invMass + bodyB._invMass + bodyA._invI * rtA + bodyB._invI * rtB;
Debug.Assert(kTangent > Settings.b2_epsilon);
ccp.tangentMass = 1.0f / kTangent;
// Setup a velocity bias for restitution.
ccp.velocityBias = 0.0f;
float vRel = Vector2.Dot(cc.normal, vB + MathUtils.Cross(wB, ccp.rB) - vA - MathUtils.Cross(wA, ccp.rA));
if (vRel < -Settings.b2_velocityThreshold)
{
ccp.velocityBias = -restitution * vRel;
}
cc.points[j] = ccp;
}
// If we have two points, then prepare the block solver.
if (cc.pointCount == 2)
{
ContactConstraintPoint ccp1 = cc.points[0];
ContactConstraintPoint ccp2 = cc.points[1];
float invMassA = bodyA._invMass;
float invIA = bodyA._invI;
float invMassB = bodyB._invMass;
float invIB = bodyB._invI;
float rn1A = MathUtils.Cross(ccp1.rA, cc.normal);
float rn1B = MathUtils.Cross(ccp1.rB, cc.normal);
float rn2A = MathUtils.Cross(ccp2.rA, cc.normal);
float rn2B = MathUtils.Cross(ccp2.rB, cc.normal);
float k11 = invMassA + invMassB + invIA * rn1A * rn1A + invIB * rn1B * rn1B;
float k22 = invMassA + invMassB + invIA * rn2A * rn2A + invIB * rn2B * rn2B;
float k12 = invMassA + invMassB + invIA * rn1A * rn2A + invIB * rn1B * rn2B;
// Ensure a reasonable condition number.
const float k_maxConditionNumber = 100.0f;
if (k11 * k11 < k_maxConditionNumber * (k11 * k22 - k12 * k12))
{
// K is safe to invert.
cc.K = new Mat22(new Vector2(k11, k12), new Vector2(k12, k22));
cc.normalMass = cc.K.GetInverse();
}
else
{
// The constraints are redundant, just use one.
// TODO_ERIN use deepest?
cc.pointCount = 1;
}
}
_constraints[i] = cc;
}
}
public void SolveVelocityConstraints()
{
for (int i = 0; i < _constraintCount; ++i)
{
ContactConstraint c = _constraints[i];
Body bodyA = c.bodyA;
Body bodyB = c.bodyB;
float wA = bodyA._angularVelocity;
float wB = bodyB._angularVelocity;
Vector2 vA = bodyA._linearVelocity;
Vector2 vB = bodyB._linearVelocity;
float invMassA = bodyA._invMass;
float invIA = bodyA._invI;
float invMassB = bodyB._invMass;
float invIB = bodyB._invI;
Vector2 normal = c.normal;
#if MATH_OVERLOADS
Vector2 tangent = ZoomEngine.Physics.Common.Math.Cross(normal, 1.0f);
#else
Vector2 tangent = new Vector2(normal.Y, -normal.X);
#endif
float friction = c.friction;
Debug.Assert(c.pointCount == 1 || c.pointCount == 2);
// Solve tangent constraints
for (int j = 0; j < c.pointCount; ++j)
{
ContactConstraintPoint ccp = c.points[j];
#if MATH_OVERLOADS
// Relative velocity at contact
Vector2 dv = vB + MathUtils.Cross(wB, ccp.rB) - vA - MathUtils.Cross(wA, ccp.rA);
// Compute tangent force
float vt = Vector2.Dot(dv, tangent);
#else
// Relative velocity at contact
Vector2 dv = new Vector2(vB.X + (-wB * ccp.rB.Y) - vA.X - (-wA * ccp.rA.Y),
vB.Y + (wB * ccp.rB.X) - vA.Y - (wA * ccp.rA.X));
// Compute tangent force
float vt = dv.X * tangent.X + dv.Y * tangent.Y;
#endif
float lambda = ccp.tangentMass * (-vt);
// MathUtils.Clamp the accumulated force
float maxFriction = friction * ccp.normalImpulse;
float newImpulse = MathUtils.Clamp(ccp.tangentImpulse + lambda, -maxFriction, maxFriction);
lambda = newImpulse - ccp.tangentImpulse;
#if MATH_OVERLOADS
// Apply contact impulse
Vector2 P = lambda * tangent;
vA -= invMassA * P;
wA -= invIA * MathUtils.Cross(ccp.rA, P);
vB += invMassB * P;
wB += invIB * MathUtils.Cross(ccp.rB, P);
#else
// Apply contact impulse
Vector2 P = new Vector2(lambda * tangent.X, lambda * tangent.Y);
vA.X -= invMassA * P.X;
vA.Y -= invMassA * P.Y;
wA -= invIA * (ccp.rA.X * P.Y - ccp.rA.Y * P.X);
vB.X += invMassB * P.X;
vB.Y += invMassB * P.Y;
wB += invIB * (ccp.rB.X * P.Y - ccp.rB.Y * P.X);
#endif
ccp.tangentImpulse = newImpulse;
c.points[j] = ccp;
}
// Solve normal constraints
if (c.pointCount == 1)
{
ContactConstraintPoint ccp = c.points[0];
#if MATH_OVERLOADS
// Relative velocity at contact
Vector2 dv = vB + MathUtils.Cross(wB, ccp.rB) - vA - MathUtils.Cross(wA, ccp.rA);
// Compute normal impulse
float vn = Vector2.Dot(dv, normal);
float lambda = -ccp.normalMass * (vn - ccp.velocityBias);
// MathUtils.Clamp the accumulated impulse
float newImpulse = Math.Max(ccp.normalImpulse + lambda, 0.0f);
lambda = newImpulse - ccp.normalImpulse;
// Apply contact impulse
Vector2 P = lambda * normal;
vA -= invMassA * P;
wA -= invIA * MathUtils.Cross(ccp.rA, P);
vB += invMassB * P;
wB += invIB * MathUtils.Cross(ccp.rB, P);
#else
// Relative velocity at contact
Vector2 dv = new Vector2(vB.X + (-wB * ccp.rB.Y) - vA.X - (-wA * ccp.rA.Y),
vB.Y + (wB * ccp.rB.X) - vA.Y - (wA * ccp.rA.X));
// Compute normal impulse
float vn = dv.X * normal.X + dv.Y * normal.Y;
float lambda = -ccp.normalMass * (vn - ccp.velocityBias);
// Clamp the accumulated impulse
float newImpulse = Math.Max(ccp.normalImpulse + lambda, 0.0f);
lambda = newImpulse - ccp.normalImpulse;
// Apply contact impulse
var P = new Vector2(lambda * normal.X, lambda * normal.Y);
vA.X -= invMassA * P.X;
vA.Y -= invMassA * P.Y;
wA -= invIA * (ccp.rA.X * P.Y - ccp.rA.Y * P.X);
vB.X += invMassB * P.X;
vB.Y += invMassB * P.Y;
wB += invIB * (ccp.rB.X * P.Y - ccp.rB.Y * P.X);
#endif
ccp.normalImpulse = newImpulse;
c.points[0] = ccp;
}
else
{
// Block solver developed in collaboration with Dirk Gregorius (back in 01/07 on Box2D_Lite).
// Build the mini LCP for this contact patch
//
// vn = A * x + b, vn >= 0, , vn >= 0, x >= 0 and vn_i * x_i = 0 with i = 1..2
//
// A = J * W * JT and J = ( -n, -r1 x n, n, r2 x n )
// b = vn_0 - velocityBias
//
// The system is solved using the "Total enumeration method" (s. Murty). The complementary constraint vn_i * x_i
// implies that we must have in any solution either vn_i = 0 or x_i = 0. So for the 2D contact problem the cases
// vn1 = 0 and vn2 = 0, x1 = 0 and x2 = 0, x1 = 0 and vn2 = 0, x2 = 0 and vn1 = 0 need to be tested. The first valid
// solution that satisfies the problem is chosen.
//
// In order to account of the accumulated impulse 'a' (because of the iterative nature of the solver which only requires
// that the accumulated impulse is clamped and not the incremental impulse) we change the impulse variable (x_i).
//
// Substitute:
//
// x = x' - a
//
// Plug into above equation:
//
// vn = A * x + b
// = A * (x' - a) + b
// = A * x' + b - A * a
// = A * x' + b'
// b' = b - A * a;
ContactConstraintPoint cp1 = c.points[0];
ContactConstraintPoint cp2 = c.points[1];
Vector2 a = new Vector2(cp1.normalImpulse, cp2.normalImpulse);
Debug.Assert(a.X >= 0.0f && a.Y >= 0.0f);
#if MATH_OVERLOADS
// Relative velocity at contact
Vector2 dv1 = vB + MathUtils.Cross(wB, cp1.rB) - vA - MathUtils.Cross(wA, cp1.rA);
Vector2 dv2 = vB + MathUtils.Cross(wB, cp2.rB) - vA - MathUtils.Cross(wA, cp2.rA);
// Compute normal velocity
float vn1 = Vector2.Dot(dv1, normal);
float vn2 = Vector2.Dot(dv2, normal);
Vector2 b = new Vector2(vn1 - cp1.velocityBias, vn2 - cp2.velocityBias);
b -= MathUtils.Multiply(ref c.K, a);
#else
// Relative velocity at contact
Vector2 dv1 = new Vector2(vB.X + (-wB * cp1.rB.Y) - vA.X - (-wA * cp1.rA.Y),
vB.Y + (wB * cp1.rB.X) - vA.Y - (wA * cp1.rA.X));
Vector2 dv2 = new Vector2(vB.X + (-wB * cp2.rB.Y) - vA.X - (-wA * cp2.rA.Y),
vB.Y + (wB * cp2.rB.X) - vA.Y - (wA * cp2.rA.X));
// Compute normal velocity
float vn1 = dv1.X * normal.X + dv1.Y * normal.Y;
float vn2 = dv2.X * normal.X + dv2.Y * normal.Y;
Vector2 b = new Vector2(vn1 - cp1.velocityBias, vn2 - cp2.velocityBias);
b -= MathUtils.Multiply(ref c.K, a); // Inlining didn't help for the multiply.
#endif
while (true)
{
//
// Case 1: vn = 0
//
// 0 = A * x' + b'
//
// Solve for x':
//
// x' = - inv(A) * b'
//
Vector2 x = -MathUtils.Multiply(ref c.normalMass, b);
if (x.X >= 0.0f && x.Y >= 0.0f)
{
#if MATH_OVERLOADS
// Resubstitute for the incremental impulse
Vector2 d = x - a;
// Apply incremental impulse
Vector2 P1 = d.X * normal;
Vector2 P2 = d.Y * normal;
vA -= invMassA * (P1 + P2);
wA -= invIA * (MathUtils.Cross(cp1.rA, P1) + MathUtils.Cross(cp2.rA, P2));
vB += invMassB * (P1 + P2);
wB += invIB * (MathUtils.Cross(cp1.rB, P1) + MathUtils.Cross(cp2.rB, P2));
#else
// Resubstitute for the incremental impulse
Vector2 d = new Vector2(x.X - a.X, x.Y - a.Y);
// Apply incremental impulse
Vector2 P1 = new Vector2(d.X * normal.X, d.X * normal.Y);
Vector2 P2 = new Vector2(d.Y * normal.X, d.Y * normal.Y);
Vector2 P12 = new Vector2(P1.X + P2.X, P1.Y + P2.Y);
vA.X -= invMassA * P12.X;
vA.Y -= invMassA * P12.Y;
wA -= invIA * ((cp1.rA.X * P1.Y - cp1.rA.Y * P1.X) + (cp2.rA.X * P2.Y - cp2.rA.Y * P2.X));
vB.X += invMassB * P12.X;
vB.Y += invMassB * P12.Y;
wB += invIB * ((cp1.rB.X * P1.Y - cp1.rB.Y * P1.X) + (cp2.rB.X * P2.Y - cp2.rB.Y * P2.X));
#endif
// Accumulate
cp1.normalImpulse = x.X;
cp2.normalImpulse = x.Y;
#if B2_DEBUG_SOLVER
float k_errorTol = 1e-3f;
// Postconditions
dv1 = vB + MathUtils.Cross(wB, cp1.rB) - vA - MathUtils.Cross(wA, cp1.rA);
dv2 = vB + MathUtils.Cross(wB, cp2.rB) - vA - MathUtils.Cross(wA, cp2.rA);
// Compute normal velocity
vn1 = Vector2.Dot(dv1, normal);
vn2 = Vector2.Dot(dv2, normal);
Debug.Assert(MathUtils.Abs(vn1 - cp1.velocityBias) < k_errorTol);
Debug.Assert(MathUtils.Abs(vn2 - cp2.velocityBias) < k_errorTol);
#endif
break;
}
//
// Case 2: vn1 = 0 and x2 = 0
//
// 0 = a11 * x1' + a12 * 0 + b1'
// vn2 = a21 * x1' + a22 * 0 + b2'
//
x.X = -cp1.normalMass * b.X;
x.Y = 0.0f;
vn1 = 0.0f;
vn2 = c.K.col1.Y * x.X + b.Y;
if (x.X >= 0.0f && vn2 >= 0.0f)
{
#if MATH_OVERLOADS
// Resubstitute for the incremental impulse
Vector2 d = x - a;
// Apply incremental impulse
Vector2 P1 = d.X * normal;
Vector2 P2 = d.Y * normal;
vA -= invMassA * (P1 + P2);
wA -= invIA * (MathUtils.Cross(cp1.rA, P1) + MathUtils.Cross(cp2.rA, P2));
vB += invMassB * (P1 + P2);
wB += invIB * (MathUtils.Cross(cp1.rB, P1) + MathUtils.Cross(cp2.rB, P2));
#else
// Resubstitute for the incremental impulse
Vector2 d = new Vector2(x.X - a.X, x.Y - a.Y);
// Apply incremental impulse
Vector2 P1 = new Vector2(d.X * normal.X, d.X * normal.Y);
Vector2 P2 = new Vector2(d.Y * normal.X, d.Y * normal.Y);
Vector2 P12 = new Vector2(P1.X + P2.X, P1.Y + P2.Y);
vA.X -= invMassA * P12.X;
vA.Y -= invMassA * P12.Y;
wA -= invIA * ((cp1.rA.X * P1.Y - cp1.rA.Y * P1.X) + (cp2.rA.X * P2.Y - cp2.rA.Y * P2.X));
vB.X += invMassB * P12.X;
vB.Y += invMassB * P12.Y;
wB += invIB * ((cp1.rB.X * P1.Y - cp1.rB.Y * P1.X) + (cp2.rB.X * P2.Y - cp2.rB.Y * P2.X));
#endif
// Accumulate
cp1.normalImpulse = x.X;
cp2.normalImpulse = x.Y;
#if B2_DEBUG_SOLVER
// Postconditions
dv1 = vB + MathUtils.Cross(wB, cp1.rB) - vA - MathUtils.Cross(wA, cp1.rA);
// Compute normal velocity
vn1 = Vector2.Dot(dv1, normal);
Debug.Assert(MathUtils.Abs(vn1 - cp1.velocityBias) < k_errorTol);
#endif
break;
}
//
// Case 3: vn2 = 0 and x1 = 0
//
// vn1 = a11 * 0 + a12 * x2' + b1'
// 0 = a21 * 0 + a22 * x2' + b2'
//
x.X = 0.0f;
x.Y = -cp2.normalMass * b.Y;
vn1 = c.K.col2.X * x.Y + b.X;
vn2 = 0.0f;
if (x.Y >= 0.0f && vn1 >= 0.0f)
{
#if MATH_OVERLOADS
// Resubstitute for the incremental impulse
Vector2 d = x - a;
// Apply incremental impulse
Vector2 P1 = d.X * normal;
Vector2 P2 = d.Y * normal;
vA -= invMassA * (P1 + P2);
wA -= invIA * (MathUtils.Cross(cp1.rA, P1) + MathUtils.Cross(cp2.rA, P2));
vB += invMassB * (P1 + P2);
wB += invIB * (MathUtils.Cross(cp1.rB, P1) + MathUtils.Cross(cp2.rB, P2));
#else
// Resubstitute for the incremental impulse
Vector2 d = new Vector2(x.X - a.X, x.Y - a.Y);
// Apply incremental impulse
Vector2 P1 = new Vector2(d.X * normal.X, d.X * normal.Y);
Vector2 P2 = new Vector2(d.Y * normal.X, d.Y * normal.Y);
Vector2 P12 = new Vector2(P1.X + P2.X, P1.Y + P2.Y);
vA.X -= invMassA * P12.X;
vA.Y -= invMassA * P12.Y;
wA -= invIA * ((cp1.rA.X * P1.Y - cp1.rA.Y * P1.X) + (cp2.rA.X * P2.Y - cp2.rA.Y * P2.X));
vB.X += invMassB * P12.X;
vB.Y += invMassB * P12.Y;
wB += invIB * ((cp1.rB.X * P1.Y - cp1.rB.Y * P1.X) + (cp2.rB.X * P2.Y - cp2.rB.Y * P2.X));
#endif
// Accumulate
cp1.normalImpulse = x.X;
cp2.normalImpulse = x.Y;
#if B2_DEBUG_SOLVER
// Postconditions
dv2 = vB + MathUtils.Cross(wB, cp2.rB) - vA - MathUtils.Cross(wA, cp2.rA);
// Compute normal velocity
vn2 = Vector2.Dot(dv2, normal);
Debug.Assert(MathUtils.Abs(vn2 - cp2.velocityBias) < k_errorTol);
#endif
break;
}
//
// Case 4: x1 = 0 and x2 = 0
//
// vn1 = b1
// vn2 = b2;
x.X = 0.0f;
x.Y = 0.0f;
vn1 = b.X;
vn2 = b.Y;
if (vn1 >= 0.0f && vn2 >= 0.0f)
{
#if MATH_OVERLOADS
// Resubstitute for the incremental impulse
Vector2 d = x - a;
// Apply incremental impulse
Vector2 P1 = d.X * normal;
Vector2 P2 = d.Y * normal;
vA -= invMassA * (P1 + P2);
wA -= invIA * (MathUtils.Cross(cp1.rA, P1) + MathUtils.Cross(cp2.rA, P2));
vB += invMassB * (P1 + P2);
wB += invIB * (MathUtils.Cross(cp1.rB, P1) + MathUtils.Cross(cp2.rB, P2));
#else
// Resubstitute for the incremental impulse
Vector2 d = new Vector2(x.X - a.X, x.Y - a.Y);
// Apply incremental impulse
Vector2 P1 = new Vector2(d.X * normal.X, d.X * normal.Y);
Vector2 P2 = new Vector2(d.Y * normal.X, d.Y * normal.Y);
Vector2 P12 = new Vector2(P1.X + P2.X, P1.Y + P2.Y);
vA.X -= invMassA * P12.X;
vA.Y -= invMassA * P12.Y;
wA -= invIA * ((cp1.rA.X * P1.Y - cp1.rA.Y * P1.X) + (cp2.rA.X * P2.Y - cp2.rA.Y * P2.X));
vB.X += invMassB * P12.X;
vB.Y += invMassB * P12.Y;
wB += invIB * ((cp1.rB.X * P1.Y - cp1.rB.Y * P1.X) + (cp2.rB.X * P2.Y - cp2.rB.Y * P2.X));
#endif
// Accumulate
cp1.normalImpulse = x.X;
cp2.normalImpulse = x.Y;
break;
}
// No solution, give up. This is hit sometimes, but it doesn't seem to matter.
break;
}
c.points[0] = cp1;
c.points[1] = cp2;
}
_constraints[i] = c;
bodyA._linearVelocity = vA;
bodyA._angularVelocity = wA;
bodyB._linearVelocity = vB;
bodyB._angularVelocity = wB;
}
}