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Add geom::subdivide for subdividing an indexed mesh

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This commit is contained in:
Nikita Lisitsa 2022-06-09 11:15:10 +03:00
parent 8e081d6d06
commit 141c707562
1 changed files with 52 additions and 0 deletions
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52
libs/geom/include/psemek/geom/mesh.hpp
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@ -156,4 +156,56 @@ namespace psemek::geom
return result;
}
template <typename Vertex, typename Index>
void subdivide(std::vector<Vertex> & vertices, std::vector<triangle<Index>> & triangles)
{
using edge = std::pair<Index, Index>;
using scalar = std::decay_t<decltype(vertices[0][0])>;
auto normalise = [](edge e) -> edge
{
if (e.first > e.second)
std::swap(e.first, e.second);
return e;
};
std::unordered_map<edge, Index> midpoints;
auto add_midpoint = [&](Index i0, Index i1)
{
auto ne = normalise({i0, i1});
if (!midpoints.contains(ne))
{
midpoints[ne] = vertices.size();
vertices.push_back(lerp(vertices[i0], vertices[i1], scalar{0.5}));
}
};
for (auto const & t : triangles)
{
add_midpoint(t[0], t[1]);
add_midpoint(t[1], t[2]);
add_midpoint(t[2], t[0]);
}
auto get_midpoint = [&](Index i0, Index i1)
{
return midpoints.at(normalise({i0, i1}));
};
std::vector<triangle<Index>> new_triangles;
for (auto const & t : triangles)
{
new_triangles.push_back({t[0], get_midpoint(t[0], t[1]), get_midpoint(t[2], t[0])});
new_triangles.push_back({t[1], get_midpoint(t[1], t[2]), get_midpoint(t[0], t[1])});
new_triangles.push_back({t[2], get_midpoint(t[2], t[0]), get_midpoint(t[1], t[2])});
new_triangles.push_back({get_midpoint(t[0], t[1]), get_midpoint(t[1], t[2]), get_midpoint(t[2], t[0])});
}
triangles.swap(new_triangles);
}
}