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Tet remeshing - improve normals computation in smoothing step #9595

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Merged
sloriot merged 2 commits into from
Aug 19, 2026
+13 −44
Merged

Tet remeshing - improve normals computation in smoothing step #9595

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3ee1d03
remove useless while loop
janetournois Aug 5, 2026
bf977ac
rename normal and add comments
janetournois Aug 5, 2026
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57 changes: 13 additions & 44 deletions Tetrahedral_remeshing/include/CGAL/Tetrahedral_remeshing/internal/smooth_vertices.h
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Original file line number Diff line number Diff line change
Expand Up @@ -339,54 +339,24 @@ class Tetrahedral_remeshing_smoother

//collect all facet normals
std::unordered_map<Facet, Vector_3, boost::hash<Facet>> fnormals;
for (const Facet& f : tr.finite_facets())
for (const Facet& trf : tr.finite_facets())
{
if (is_boundary(c3t3, f, m_cell_selector))
{
const Facet cf = canonical_facet(f);
fnormals[cf] = CGAL::NULL_VECTOR;
}
}

for (const auto& fn : fnormals)
{
if(fn.second != CGAL::NULL_VECTOR)
if(!is_boundary(c3t3, trf, m_cell_selector))
continue;

const Facet& f = fn.first;
const Facet& mf = tr.mirror_facet(f);
CGAL_expensive_assertion(is_boundary(c3t3, f, m_cell_selector));

Vector_3 start_ref = CGAL::Tetrahedral_remeshing::normal(f, tr.geom_traits());
if (c3t3.triangulation().is_infinite(mf.first)
|| c3t3.subdomain_index(mf.first) < c3t3.subdomain_index(f.first))
start_ref = opp(start_ref);
fnormals[f] = start_ref;
const Facet f = canonical_facet(trf);
const Cell_handle c = f.first;
const Cell_handle neigh = f.first->neighbor(f.second);

std::list<Facet> facets;
facets.push_back(f);
while (!facets.empty())
{
const Facet ff = facets.front();
facets.pop_front();
Vector_3 n = CGAL::Tetrahedral_remeshing::normal(f, tr.geom_traits());
if (c3t3.triangulation().is_infinite(neigh)
|| c3t3.subdomain_index(neigh) < c3t3.subdomain_index(c))
n = opp(n);

const Vector_3& ref = fnormals[ff];
for (const Edge& ei : facet_edges(ff.first, ff.second, tr))
{
if (std::optional<Facet> neighbor
= find_adjacent_facet_on_surface(ff, ei, c3t3))
{
const Facet neigh = *neighbor; //already a canonical_facet
if (fnormals[neigh] == CGAL::NULL_VECTOR) //check it's not already computed
{
fnormals[neigh] = compute_normal(neigh, ref, gt);
facets.push_back(neigh);
}
}
}
}
fnormals[f] = n; // n has length equal to the area of the facet
}

// accumulate the normals in normals_map
#ifdef CGAL_TETRAHEDRAL_REMESHING_DEBUG
std::ofstream osf("dump_facet_normals.polylines.txt");
#endif
Expand All @@ -401,9 +371,8 @@ class Tetrahedral_remeshing_smoother
for (const Vertex_handle vi : tr.vertices(f))
{
typename VertexNormalsMap::iterator patch_vector_it = normals_map.find(vi);

if (patch_vector_it == normals_map.end()
|| patch_vector_it->second.find(surf_i) == patch_vector_it->second.end())
if ( patch_vector_it == normals_map.end() //vertex not found
|| patch_vector_it->second.find(surf_i) == patch_vector_it->second.end())//patch not found
{
normals_map[vi][surf_i] = n;
}
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