protected override void Draw(Settings settings)
{
base.Draw(settings);
b2Manifold manifold = new b2Manifold();
b2Collision.b2CollidePolygons(manifold, m_polygonA, ref m_transformA, m_polygonB, ref m_transformB);
b2WorldManifold worldManifold = new b2WorldManifold();
worldManifold.Initialize(manifold, ref m_transformA, m_polygonA.Radius, ref m_transformB, m_polygonB.Radius);
m_debugDraw.DrawString(5, m_textLine, "point count = {0}", manifold.pointCount);
m_textLine += 15;
{
b2Color color = new b2Color(0.9f, 0.9f, 0.9f);
b2Vec2[] v = new b2Vec2[b2Settings.b2_maxPolygonVertices];
for (int i = 0; i < m_polygonA.VertexCount; ++i)
{
v[i] = b2Math.b2Mul(m_transformA, m_polygonA.Vertices[i]);
}
m_debugDraw.DrawPolygon(v, m_polygonA.VertexCount, color);
for (int i = 0; i < m_polygonB.VertexCount; ++i)
{
v[i] = b2Math.b2Mul(m_transformB, m_polygonB.Vertices[i]);
}
m_debugDraw.DrawPolygon(v, m_polygonB.VertexCount, color);
}
for (int i = 0; i < manifold.pointCount; ++i)
{
m_debugDraw.DrawPoint(worldManifold.points[i], 4.0f, new b2Color(0.9f, 0.3f, 0.3f));
}
}
// 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.Create(), xfB = b2Transform.Create();
xfA.q.Set(aA);
xfB.q.Set(aB);
xfA.p = cA - b2Math.b2Mul(xfA.q, localCenterA);
xfB.p = cB - b2Math.b2Mul(xfB.q, 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(vcp.rA, vc.normal);
float rnB = b2Math.b2Cross(vcp.rB, vc.normal);
float kNormal = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
vcp.normalMass = kNormal > 0.0f ? 1.0f / kNormal : 0.0f;
b2Vec2 tangent = b2Math.b2Cross(vc.normal, 1.0f);
float rtA = b2Math.b2Cross(vcp.rA, tangent);
float rtB = b2Math.b2Cross(vcp.rB, 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, vcp.rB) - vA - b2Math.b2Cross(wA, 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(vcp1.rA, vc.normal);
float rn1B = b2Math.b2Cross(vcp1.rB, vc.normal);
float rn2A = b2Math.b2Cross(vcp2.rA, vc.normal);
float rn2B = b2Math.b2Cross(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.
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 virtual void GetWorldManifold(b2WorldManifold worldManifold)
{
b2Body bodyA = m_fixtureA.Body;
b2Body bodyB = m_fixtureB.Body;
b2Shape shapeA = m_fixtureA.Shape;
b2Shape shapeB = m_fixtureB.Shape;
worldManifold.Initialize(ref m_manifold, bodyA.Transform, shapeA.Radius, bodyB.Transform, shapeB.Radius);
}
public override void PreSolve(Box2D.Dynamics.Contacts.b2Contact contact, ref Box2D.Collision.b2Manifold oldManifold)
{
b2Manifold manifold = contact.GetManifold();
if (manifold.pointCount == 0)
{
return;
}
b2Fixture fixtureA = contact.GetFixtureA();
b2Fixture fixtureB = contact.GetFixtureB();
b2PointState[] state1 = new b2PointState[b2Settings.b2_maxManifoldPoints];
b2PointState[] state2 = new b2PointState[b2Settings.b2_maxManifoldPoints];
b2Collision.b2GetPointStates(state1, state2, ref oldManifold, ref manifold);
b2WorldManifold worldManifold = new b2WorldManifold();
contact.GetWorldManifold(ref worldManifold);
for (int i = 0; i < manifold.pointCount && m_pointCount < k_maxContactPoints; ++i)
{
ContactPoint cp = m_points[m_pointCount];
cp.fixtureA = fixtureA;
cp.fixtureB = fixtureB;
cp.position = worldManifold.points[i];
cp.normal = worldManifold.normal;
cp.state = state2[i];
m_points[m_pointCount] = cp;
++m_pointCount;
}
}