// Find TOI contacts and solve them.
public void SolveTOI(b2TimeStep step)
{
b2Island island = new b2Island(2 * b2Settings.b2_maxTOIContacts, b2Settings.b2_maxTOIContacts, 0, m_contactManager.ContactListener);
if (m_stepComplete)
{
for (b2Body b = m_bodyList; b; b = b.Next)
{
b.BodyFlags &= ~b2Body.e_islandFlag;
b.m_sweep.alpha0 = 0.0f;
}
for (b2Contact c = m_contactManager.ContactList; c; c = c.Next)
{
// Invalidate TOI
c.ContactFlags &= ~(b2ContactType.e_toiFlag | b2ContactType.e_islandFlag);
c.m_toiCount = 0;
c.m_toi = 1.0f;
}
}
// Find TOI events and solve them.
for (; ;)
{
// Find the first TOI.
b2Contact minContact = null;
float minAlpha = 1.0f;
for (b2Contact c = m_contactManager.ContactList; c != null; c = c.Next)
{
// Is this contact disabled?
if (c.IsEnabled() == false)
{
continue;
}
// Prevent excessive sub-stepping.
if (c.m_toiCount > b2Settings.b2_maxSubSteps)
{
continue;
}
float alpha = 1.0f;
if (c.ContactFlags.HasFlag(b2ContactFlags.e_toiFlag))
{
// This contact has a valid cached TOI.
alpha = c.m_toi;
}
else
{
b2Fixture fA = c.GetFixtureA();
b2Fixture fB = c.GetFixtureB();
// Is there a sensor?
if (fA.IsSensor || fB.IsSensor)
{
continue;
}
b2Body bA = fA.Body;
b2Body bB = fB.Body;
b2BodyType typeA = bA.BodyType;
b2BodyType typeB = bB.BodyType;
bool activeA = bA.IsAwake() && typeA != b2BodyType.b2_staticBody;
bool activeB = bB.IsAwake() && typeB != b2BodyType.b2_staticBody;
// Is at least one body active (awake and dynamic or kinematic)?
if (activeA == false && activeB == false)
{
continue;
}
bool collideA = bA.IsBullet() || typeA != b2BodyType.b2_dynamicBody;
bool collideB = bB.IsBullet() || typeB != b2BodyType.b2_dynamicBody;
// Are these two non-bullet dynamic bodies?
if (collideA == false && collideB == false)
{
continue;
}
// Compute the TOI for this contact.
// Put the sweeps onto the same time interval.
float alpha0 = bA.Sweep.alpha0;
if (bA.Sweep.alpha0 < bB.Sweep.alpha0)
{
alpha0 = bB.Sweep.alpha0;
bA.Sweep.Advance(alpha0);
}
else if (bB.Sweep.alpha0 < bA.Sweep.alpha0)
{
alpha0 = bA.Sweep.alpha0;
bB.Sweep.Advance(alpha0);
}
int indexA = c.GetChildIndexA();
int indexB = c.GetChildIndexB();
// Compute the time of impact in interval [0, minTOI]
b2TOIInput input = new b2TOIInput();
input.proxyA.Set(fA.Shape, indexA);
input.proxyB.Set(fB.Shape, indexB);
input.sweepA = bA.Sweep;
input.sweepB = bB.Sweep;
input.tMax = 1.0f;
b2TOIOutput output = b2TimeOfImpact(input);
// Beta is the fraction of the remaining portion of the .
float beta = output.t;
if (output.state == b2TOIOutputType.e_touching)
{
alpha = b2Math.b2Min(alpha0 + (1.0f - alpha0) * beta, 1.0f);
}
else
{
alpha = 1.0f;
}
c.m_toi = alpha;
c.ContactFlags |= b2ContactFlags.e_toiFlag;
}
if (alpha < minAlpha)
{
// This is the minimum TOI found so far.
minContact = c;
minAlpha = alpha;
}
}
if (minContact == null || 1.0f - 10.0f * b2Settings.b2_epsilon < minAlpha)
{
// No more TOI events. Done!
m_stepComplete = true;
break;
}
{
// Advance the bodies to the TOI.
b2Fixture fA = minContact.GetFixtureA();
b2Fixture fB = minContact.GetFixtureB();
b2Body bA = fA.Body;
b2Body bB = fB.Body;
b2Sweep backup1 = bA.Sweep;
b2Sweep backup2 = bB.Sweep;
bA.Advance(minAlpha);
bB.Advance(minAlpha);
// The TOI contact likely has some new contact points.
minContact.Update(m_contactManager.ContactListener);
minContact.ContactFlags &= ~b2ContactFlags.e_toiFlag;
++minContact.m_toiCount;
// Is the contact solid?
if (minContact.IsEnabled() == false || minContact.IsTouching() == false)
{
// Restore the sweeps.
minContact.SetEnabled(false);
bA.Sweep = backup1;
bB.Sweep = backup2;
bA.SynchronizeTransform();
bB.SynchronizeTransform();
continue;
}
bA.SetAwake(true);
bB.SetAwake(true);
// Build the island
island.Clear();
island.Add(bA);
island.Add(bB);
island.Add(minContact);
bA.BodyFlags |= b2BodyFlags.e_islandFlag;
bB.BodyFlags |= b2BodyFlags.e_islandFlag;
minContact.ContentType |= b2ContactFlags.e_islandFlag;
// Get contacts on bodyA and bodyB.
b2Body[] bodies = new b2Body[] { bA, bB };
for (int i = 0; i < 2; ++i)
{
b2Body body = bodies[i];
if (body.BodyType == b2BodyType.b2_dynamicBody)
{
for (b2ContactEdge ce = body.ContactList; ce != null; ce = ce.next)
{
if (island.BodyCount == island.BodyCapacity)
{
break;
}
if (island.ContactCount == island.ContactCapacity)
{
break;
}
b2Contact contact = ce.contact;
// Has this contact already been added to the island?
if (contact.ContactType & b2ContactType.e_islandFlag)
{
continue;
}
// Only add static, kinematic, or bullet bodies.
b2Body other = ce.other;
if (other.BodyType == b2BodyType.b2_dynamicBody &&
body.IsBullet() == false && other.IsBullet() == false)
{
continue;
}
// Skip sensors.
bool sensorA = contact.m_fixtureA.m_isSensor;
bool sensorB = contact.m_fixtureB.m_isSensor;
if (sensorA || sensorB)
{
continue;
}
// Tentatively advance the body to the TOI.
b2Sweep backup = other.Sweep;
if (other.BodyFlags.HasFlag(b2BodyFlags.e_islandFlag))
{
other.Advance(minAlpha);
}
// Update the contact points
contact.Update(m_contactManager.ContactListener);
// Was the contact disabled by the user?
if (contact.IsEnabled() == false)
{
other.Sweep = backup;
other.SynchronizeTransform();
continue;
}
// Are there contact points?
if (contact.IsTouching() == false)
{
other.Sweep = backup;
other.SynchronizeTransform();
continue;
}
// Add the contact to the island
contact.ContactFlags |= b2ContactFlags.e_islandFlag;
island.Add(contact);
// Has the other body already been added to the island?
if (other.BodyFlags.HasFlag(b2BodyFlags.e_islandFlag))
{
continue;
}
// Add the other body to the island.
other.BodyFlags |= b2BodyFlags.e_islandFlag;
if (other.BodyType != b2BodyType.b2_staticBody)
{
other.SetAwake(true);
}
island.Add(other);
}
}
}
b2TimeStep subStep;
subStep.dt = (1.0f - minAlpha) * step.dt;
subStep.inv_dt = 1.0f / subStep.dt;
subStep.dtRatio = 1.0f;
subStep.positionIterations = 20;
subStep.velocityIterations = step.velocityIterations;
subStep.warmStarting = false;
island.SolveTOI(subStep, bA.m_islandIndex, bB.m_islandIndex);
// Reset island flags and synchronize broad-phase proxies.
for (int i = 0; i < island.m_bodyCount; ++i)
{
b2Body body = island.m_bodies[i];
body.BodyFlags &= ~b2BodyFlags.e_islandFlag;
if (body.BodyType != b2BodyType.b2_dynamicBody)
{
continue;
}
body.SynchronizeFixtures();
// Invalidate all contact TOIs on this displaced body.
for (b2ContactEdge ce = body.ContactList; ce != null; ce = ce.next)
{
ce.Contact.ContactFlags &= ~(b2ContactFlags.e_toiFlag | b2ContactFlags.e_islandFlag);
}
}
// Commit fixture proxy movements to the broad-phase so that new contacts are created.
// Also, some contacts can be destroyed.
m_contactManager.FindNewContacts();
if (m_subStepping)
{
m_stepComplete = false;
break;
}
}
}
}