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; } }