internal void CleanUp()
{
isActive = true;
deactivationCandidateCount = 0;
memberCount = 0;
immediateParent = this;
}
private SimulationIsland Merge(SimulationIsland s1, SimulationIsland s2)
{
//Pull the smaller island into the larger island and set all members
//of the smaller island to refer to the new island.
//The simulation islands can be null; a connection can be a kinematic entity, which has no simulation island.
//'Merging' a null island with an island simply gets back the island.
if (s1 == null)
{
//Should still activate the island, though.
s2.IsActive = true;
return(s2);
}
if (s2 == null)
{
//Should still activate the island, though.
s1.IsActive = true;
return(s1);
}
//Swap if needed so s1 is the bigger island
if (s1.memberCount < s2.memberCount)
{
var biggerIsland = s2;
s2 = s1;
s1 = biggerIsland;
}
s1.IsActive = true;
s2.immediateParent = s1;
//This is a bit like a 'union by rank.'
//But don't get confused- simulation islands are not a union find structure.
//This parenting simply avoids the need for maintaining a list of members in each simulation island.
//In the subsequent frame, the deactivation candidacy update will go through the parents and eat away
//at the child simulation island. Then, in a later TryToDeactivate phase, the then-empty simulation island
//will be removed.
//The larger one survives.
return(s1);
}
///<summary>
/// Adds a simulation island to a member.
///</summary>
///<param name="member">Member to gain a simulation island.</param>
///<exception cref="Exception">Thrown if the member already has a simulation island.</exception>
public void AddSimulationIslandToMember(SimulationIslandMember member)
{
if (member.SimulationIsland != null)
{
throw new ArgumentException("Cannot initialize member's simulation island; it already has one.");
}
if (member.connections.Count > 0)
{
SimulationIsland island = null;
//Find a simulation starting island to live in.
for (int i = 0; i < member.connections.Count; i++)
{
for (int j = 0; j < member.connections.Elements[i].entries.Count; j++)
{
island = member.connections.Elements[i].entries.Elements[j].Member.SimulationIsland;
if (island != null)
{
island.Add(member);
break;
}
}
if (island != null)
{
break;
}
}
if (member.SimulationIsland == null)
{
//No non-null entries in any connections. That's weird.
//Maybe it's connected to a bunch of kinematics, or maybe it's a vehicle-like situation
//where the body is associated with a 'vehicle' connection which sometimes contains only the body.
//No friends to merge with.
SimulationIsland newIsland = islandPool.Take();
simulationIslands.Add(newIsland);
newIsland.Add(member);
return;
}
//Becoming dynamic adds a new path.
//Merges must be attempted between its connected members.
for (int i = 0; i < member.connections.Count; i++)
{
for (int j = 0; j < member.connections.Elements[i].entries.Count; j++)
{
if (member.connections.Elements[i].entries.Elements[j].Member == member)
{
continue; //Don't bother trying to compare against ourselves. That would cause an erroneous early-out sometimes.
}
SimulationIsland opposingIsland = member.connections.Elements[i].entries.Elements[j].Member.SimulationIsland;
if (opposingIsland != null)
{
if (island != opposingIsland)
{
island = Merge(island, opposingIsland);
}
//All non-null simulation islands in a single connection are guaranteed to be the same island due to previous merges.
//Once we find one, we can stop.
break;
}
}
}
}
else
{
//No friends to merge with.
SimulationIsland newIsland = islandPool.Take();
simulationIslands.Add(newIsland);
newIsland.Add(member);
}
}
///<summary>
/// Strips a member of its simulation island.
///</summary>
///<param name="member">Member to be stripped.</param>
public void RemoveSimulationIslandFromMember(SimulationIslandMember member)
{
//Becoming kinematic eliminates the member as a possible path.
//Splits must be attempted between its connected members.
//Don't need to split same-connection members. Splitting one non-null entry against a non null entry in each of the other connections will do the trick.
if (member.simulationIsland != null)
{
//Note that this is using the most immediate simulation island. This is because the immediate simulation island
//is the one who 'owns' the member; not the root parent. The root parent will own the member in the next frame
//after the deactivation candidacy loop runs.
SimulationIsland island = member.simulationIsland;
island.Remove(member);
if (island.memberCount == 0)
{
//Even though we appear to have connections, the island was only me!
//We can stop now.
//Note that we do NOT remove the island from the simulation islands list here.
//That would take an O(n) search. Instead, orphan it and let the TryToDeactivate loop find it.
return;
}
}
if (member.connections.Count > 0)
{
for (int i = 0; i < member.connections.Count; i++)
{
//Find a member with a non-null island to represent connection i.
SimulationIslandMember representativeA = null;
for (int j = 0; j < member.connections.Elements[i].entries.Count; j++)
{
if (member.connections.Elements[i].entries.Elements[j].Member.SimulationIsland != null)
{
representativeA = member.connections.Elements[i].entries.Elements[j].Member;
break;
}
}
if (representativeA == null)
{
//There was no representative! That means it was a connection in which
//no member had a simulation island. Consider removing a dynamic box from the space
//while it sits on a kinematic box. Neither object has a simulation island.
//In this case, simply try the next connection.
continue;
}
//Activate the representative. This must be performed even if no split occurs; connected objects must be activated!
representativeA.Activate();
//Split the representative against representatives from other connections.
for (int j = i + 1; j < member.connections.Count; j++)
{
//Find a representative for another connection.
SimulationIslandMember representativeB = null;
for (int k = 0; k < member.connections.Elements[j].entries.Count; k++)
{
if (member.connections.Elements[j].entries.Elements[k].Member.SimulationIsland != null)
{
representativeB = member.connections.Elements[j].entries.Elements[k].Member;
break;
}
}
if (representativeB == null)
{
//There was no representative! Same idea as above.
//Try the next connection.
continue;
}
//Activate the representative. This must be performed even if no split occurs; connected objects must be activated!
representativeB.Activate();
//Try to split the representatives.
//Don't bother doing any deferring; this is a rare activity
//and it's best just to do it up front.
TryToSplit(representativeA, representativeB);
}
}
}
}
/// <summary>
/// Tries to split connections between the two island members.
/// </summary>
/// <param name="member1">First island member.</param>
/// <param name="member2">Second island member.</param>
/// <returns>Whether a split operation was run. This does not mean a split was
/// successful, just that the expensive test was performed.</returns>
private bool TryToSplit(SimulationIslandMember member1, SimulationIslandMember member2)
{
//Can't split if they aren't even in the same island.
//This also covers the case where the connection involves a kinematic entity that has no
//simulation island at all.
if (member1.SimulationIsland != member2.SimulationIsland ||
member1.SimulationIsland == null ||
member2.SimulationIsland == null)
{
return(false);
}
//By now, we know the members belong to the same island and are not null.
//Start a BFS starting from each member.
//Two-way can complete the search quicker.
member1Friends.Enqueue(member1);
member2Friends.Enqueue(member2);
searchedMembers1.Add(member1);
searchedMembers2.Add(member2);
member1.searchState = SimulationIslandSearchState.OwnedByFirst;
member2.searchState = SimulationIslandSearchState.OwnedBySecond;
while (member1Friends.Count > 0 && member2Friends.Count > 0)
{
SimulationIslandMember currentNode = member1Friends.Dequeue();
for (int i = 0; i < currentNode.connections.Count; i++)
{
for (int j = 0; j < currentNode.connections.Elements[i].entries.Count; j++)
{
SimulationIslandMember connectedNode;
if ((connectedNode = currentNode.connections.Elements[i].entries.Elements[j].Member) != currentNode &&
connectedNode.SimulationIsland != null) //The connection could be connected to something that isn't in the Space and has no island, or it's not dynamic.
{
switch (connectedNode.searchState)
{
case SimulationIslandSearchState.Unclaimed:
//Found a new friend :)
member1Friends.Enqueue(connectedNode);
connectedNode.searchState = SimulationIslandSearchState.OwnedByFirst;
searchedMembers1.Add(connectedNode);
break;
case SimulationIslandSearchState.OwnedBySecond:
//Found our way to member2Friends set; cannot split!
member1Friends.Clear();
member2Friends.Clear();
goto ResetSearchStates;
}
}
}
}
currentNode = member2Friends.Dequeue();
for (int i = 0; i < currentNode.connections.Count; i++)
{
for (int j = 0; j < currentNode.connections.Elements[i].entries.Count; j++)
{
SimulationIslandMember connectedNode;
if ((connectedNode = currentNode.connections.Elements[i].entries.Elements[j].Member) != currentNode &&
connectedNode.SimulationIsland != null) //The connection could be connected to something that isn't in the Space and has no island, or it's not dynamic.
{
switch (connectedNode.searchState)
{
case SimulationIslandSearchState.Unclaimed:
//Found a new friend :)
member2Friends.Enqueue(connectedNode);
connectedNode.searchState = SimulationIslandSearchState.OwnedBySecond;
searchedMembers2.Add(connectedNode);
break;
case SimulationIslandSearchState.OwnedByFirst:
//Found our way to member1Friends set; cannot split!
member1Friends.Clear();
member2Friends.Clear();
goto ResetSearchStates;
}
}
}
}
}
//If one of the queues empties out without finding anything, it means it's isolated. The other one will never find it.
//Now we can do a split. Grab a new Island, fill it with the isolated search stuff. Remove the isolated search stuff from the old Island.
SimulationIsland newIsland = islandPool.Take();
simulationIslands.Add(newIsland);
if (member1Friends.Count == 0)
{
//Member 1 is isolated, give it its own simulation island!
for (int i = 0; i < searchedMembers1.Count; i++)
{
searchedMembers1[i].simulationIsland.Remove(searchedMembers1[i]);
newIsland.Add(searchedMembers1[i]);
}
member2Friends.Clear();
}
else if (member2Friends.Count == 0)
{
//Member 2 is isolated, give it its own simulation island!
for (int i = 0; i < searchedMembers2.Count; i++)
{
searchedMembers2[i].simulationIsland.Remove(searchedMembers2[i]);
newIsland.Add(searchedMembers2[i]);
}
member1Friends.Clear();
}
//Force the system awake.
//Technically, the members should already be awake.
//However, calling Activate on them resets the members'
//deactivation candidacy timers. This prevents the island
//from instantly going back to sleep, which could leave
//objects hanging in mid-air.
member1.Activate();
member2.Activate();
ResetSearchStates:
for (int i = 0; i < searchedMembers1.Count; i++)
{
searchedMembers1[i].searchState = SimulationIslandSearchState.Unclaimed;
}
for (int i = 0; i < searchedMembers2.Count; i++)
{
searchedMembers2[i].searchState = SimulationIslandSearchState.Unclaimed;
}
searchedMembers1.Clear();
searchedMembers2.Clear();
return(true);
}
void GiveBackIsland(SimulationIsland island)
{
island.CleanUp();
islandPool.GiveBack(island);
}