//{CodeReview:Triangulation}
EarClipper::EarClipper(const Polygon2D_t& polygon, const std::vector<const Polygon2D_t*>& innerPolygons)
{
if (polygon.IsWellDefined())
{
FVector3 checkNormal = Vec3D::ZAxis();
polygonWinding = polygon.GetWinding(checkNormal);
for (std::size_t pointIndex = 0, numPoints = polygon.NumPoints(); pointIndex < numPoints; ++pointIndex)
{
vertices.push_back( Vertex(&polygon[pointIndex]) );
}
MakeSimple(innerPolygons, checkNormal);
}
}
// Main function.
// Process a set of blocks with specified entries, returns a shape
// The Make* functions receive a NextEntries. If they fill it with data, those are the entries for the
// ->Next block on them, and the blocks are what remains in Blocks (which Make* modify). In this way
// we avoid recursing on Next (imagine a long chain of Simples, if we recursed we could blow the stack).
Shape *Process(BlockSet &Blocks, BlockSet& InitialEntries, Shape *Prev) {
PrintDebug("Process() called\n");
BlockSet *Entries = &InitialEntries;
BlockSet TempEntries[2];
int CurrTempIndex = 0;
BlockSet *NextEntries;
Shape *Ret = NULL;
#define Make(call) \
Shape *Temp = call; \
if (Prev) Prev->Next = Temp; \
if (!Ret) Ret = Temp; \
if (!NextEntries->size()) { PrintDebug("Process() returning\n"); return Ret; } \
Prev = Temp; \
Entries = NextEntries; \
continue;
while (1) {
PrintDebug("Process() running\n");
DebugDump(Blocks, " blocks : ");
DebugDump(*Entries, " entries: ");
CurrTempIndex = 1-CurrTempIndex;
NextEntries = &TempEntries[CurrTempIndex];
NextEntries->clear();
if (Entries->size() == 0) return Ret;
if (Entries->size() == 1) {
Block *Curr = *(Entries->begin());
if (Curr->BranchesIn.size() == 0) {
// One entry, no looping ==> Simple
Make(MakeSimple(Blocks, Curr, *NextEntries));
}
// One entry, looping ==> Loop
Make(MakeLoop(Blocks, *Entries, *NextEntries));
}
// More than one entry, try to eliminate through a Multiple groups of
// independent blocks from an entry/ies. It is important to remove through
// multiples as opposed to looping since the former is more performant.
BlockBlockSetMap IndependentGroups;
FindIndependentGroups(Blocks, *Entries, IndependentGroups);
PrintDebug("Independent groups: %d\n", IndependentGroups.size());
if (IndependentGroups.size() > 0) {
// We can handle a group in a multiple if its entry cannot be reached by another group.
// Note that it might be reachable by itself - a loop. But that is fine, we will create
// a loop inside the multiple block (which is the performant order to do it).
for (BlockBlockSetMap::iterator iter = IndependentGroups.begin(); iter != IndependentGroups.end();) {
Block *Entry = iter->first;
BlockSet &Group = iter->second;
BlockBlockSetMap::iterator curr = iter++; // iterate carefully, we may delete
for (BlockBranchMap::iterator iterBranch = Entry->BranchesIn.begin(); iterBranch != Entry->BranchesIn.end(); iterBranch++) {
Block *Origin = iterBranch->first;
if (Group.find(Origin) == Group.end()) {
// Reached from outside the group, so we cannot handle this
PrintDebug("Cannot handle group with entry %d because of incoming branch from %d\n", Entry->Id, Origin->Id);
IndependentGroups.erase(curr);
break;
}
}
}
// As an optimization, if we have 2 independent groups, and one is a small dead end, we can handle only that dead end.
// The other then becomes a Next - without nesting in the code and recursion in the analysis.
// TODO: if the larger is the only dead end, handle that too
// TODO: handle >2 groups
// TODO: handle not just dead ends, but also that do not branch to the NextEntries. However, must be careful
// there since we create a Next, and that Next can prevent eliminating a break (since we no longer
// naturally reach the same place), which may necessitate a one-time loop, which makes the unnesting
// pointless.
if (IndependentGroups.size() == 2) {
// Find the smaller one
BlockBlockSetMap::iterator iter = IndependentGroups.begin();
Block *SmallEntry = iter->first;
int SmallSize = iter->second.size();
iter++;
Block *LargeEntry = iter->first;
int LargeSize = iter->second.size();
if (SmallSize != LargeSize) { // ignore the case where they are identical - keep things symmetrical there
if (SmallSize > LargeSize) {
Block *Temp = SmallEntry;
SmallEntry = LargeEntry;
LargeEntry = Temp; // Note: we did not flip the Sizes too, they are now invalid. TODO: use the smaller size as a limit?
}
// Check if dead end
bool DeadEnd = true;
BlockSet &SmallGroup = IndependentGroups[SmallEntry];
for (BlockSet::iterator iter = SmallGroup.begin(); iter != SmallGroup.end(); iter++) {
Block *Curr = *iter;
for (BlockBranchMap::iterator iter = Curr->BranchesOut.begin(); iter != Curr->BranchesOut.end(); iter++) {
Block *Target = iter->first;
if (SmallGroup.find(Target) == SmallGroup.end()) {
DeadEnd = false;
break;
}
}
if (!DeadEnd) break;
}
if (DeadEnd) {
PrintDebug("Removing nesting by not handling large group because small group is dead end\n");
IndependentGroups.erase(LargeEntry);
}
}
}
PrintDebug("Handleable independent groups: %d\n", IndependentGroups.size());
if (IndependentGroups.size() > 0) {
// Some groups removable ==> Multiple
Make(MakeMultiple(Blocks, *Entries, IndependentGroups, Prev, *NextEntries));
}
}
// No independent groups, must be loopable ==> Loop
Make(MakeLoop(Blocks, *Entries, *NextEntries));
}
}