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Modify subdomain labeling strategy in CDT3 -> TetRemesh triangulation 

Use a flood algorithm to mark constrained connected components.
The connected component containing the infinite vertex is marked with index 0.
Nested components are marked with increasing indices.
Disconnected components that have the same nesting level get the same index parity:
for example two cubes within a larger bounding box will be index 2 and 4.
This commit is contained in:
Mael Rouxel-Labbé 2025-11-05 09:36:56 +01:00
parent 837939c8ee
commit fd178ca9e0
1 changed files with 67 additions and 13 deletions
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80
Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
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@ -4293,23 +4293,77 @@ auto get_remeshing_triangulation(Conforming_constrained_Delaunay_triangulation_3
}
} else {
for(auto ch : tr.all_cell_handles()) {
ch->set_subdomain_index(1);
ch->set_subdomain_index(-1);
}
std::stack<decltype(tr.infinite_cell())> stack;
stack.push(tr.infinite_cell());
while(!stack.empty()) {
auto ch = stack.top();
stack.pop();
ch->set_subdomain_index(0);
for(int i = 0; i < 4; ++i) {
if(ch->ccdt_3_data().is_facet_constrained(i))
continue;
auto n = ch->neighbor(i);
if(n->subdomain_index() == 1) {
stack.push(n);
// Use a flood algorithm to mark constrained connected components.
// The connected component containing the infinite vertex is marked with index 0.
// Nested components are marked with increasing indices.
// Disconnected components that have the same nesting level get the same index parity:
// for example two cubes within a larger bounding box will be index 2 and 4.
std::list<typename Tr::Facet> border;
int next_even_subdomain = 0;
int next_odd_subdomain = 1;
// Function to flood-fill a connected component with a given subdomain index
auto flood_component = [&tr, &border](typename Tr::Cell_handle start, int subdomain_index) {
if(start->subdomain_index() != -1)
return;
std::list<typename Tr::Cell_handle> queue;
queue.push_back(start);
while(!queue.empty()) {
auto ch = queue.front();
queue.pop_front();
if(ch->subdomain_index() == -1) {
ch->set_subdomain_index(subdomain_index);
for(int i = 0; i < 4; i++) {
typename Tr::Facet f(ch, i);
auto n = ch->neighbor(i);
if(n->subdomain_index() == -1) {
if(ch->ccdt_3_data().is_facet_constrained(i))
border.push_back(f);
else
queue.push_back(n);
}
}
}
}
};
// Start with the infinite cell's component using index 0
flood_component(tr.infinite_cell(), next_even_subdomain);
next_even_subdomain += 2;
for (;;) { // while there are unvisited cells
while(!border.empty()) {
auto f = border.front();
border.pop_front();
auto n = f.first->neighbor(f.second);
if(n->subdomain_index() == -1) {
// If we are coming from an even subdomain, use next odd, and vice versa
bool from_even = (f.first->subdomain_index() % 2 == 0);
int next_index = from_even ? next_odd_subdomain : next_even_subdomain;
flood_component(n, next_index);
if(from_even)
next_odd_subdomain += 2;
else
next_even_subdomain += 2;
}
}
bool found_unvisited = false;
for(auto ch : tr.finite_cell_handles()) {
if(ch->subdomain_index() == -1) {
flood_component(ch, next_even_subdomain);
next_even_subdomain += 2;
found_unvisited = true;
break;
}
}
if(!found_unvisited)
break;
}
for(auto f : tr.finite_facets())