TriEdgeSwap.cpp

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#include "TriEdgeSwap.hpp"
 
#include <wmtk/Mesh.hpp>
 
namespace wmtk::operations::composite {
 
TriEdgeSwap::TriEdgeSwap(Mesh& m)
    : Operation(m)
    , m_split(m)
    , m_collapse(m)
{}
 
 
std::vector<simplex::Simplex> TriEdgeSwap::execute(const simplex::Simplex& simplex)
{
    // input
    //    / \.
    //   /   \ .
    //  /  f  \ .
    // X--->---
    //  \     /
    //   \   /
    //    \ /
    const auto split_simplicies = m_split(simplex);
    if (split_simplicies.empty()) return {};
    assert(split_simplicies.size() == 1);
 
    // after split
    //    /|\ .
    //   / | \ .
    //  /  | f\ .
    //  ---X-->
    //  \  |  /
    //   \ | /
    //    \|/
 
    // switch also face to keep edge orientation
    const Tuple collapse_input_tuple = mesh().switch_tuples(
        split_simplicies.front().tuple(),
        {PrimitiveType::Edge, PrimitiveType::Triangle});
    // switch edge - switch face
    //    /|\ .
    //   / ^ \ .
    //  /f |  \ .
    //  ---X---
    //  \  |  /
    //   \ | /
    //    \|/
    const auto collapse_simplicies =
        m_collapse(simplex::Simplex(mesh(), m_collapse.primitive_type(), collapse_input_tuple));
    if (collapse_simplicies.empty()) return {};
    assert(collapse_simplicies.size() == 1);
 
    // collapse output
    //     X
    //    /|\ .
    //   < | \ .
    //  /  |  \ .
    // | f |   |
    //  \  |  /
    //   \ | /
    //    \|/
    // adjust return tuple to be the swapped edge in the same orientation as the input
    const Tuple output_tuple = mesh().switch_tuples(
        collapse_simplicies.front().tuple(),
        {PrimitiveType::Edge, PrimitiveType::Vertex});
 
    return {simplex::Simplex::edge(mesh(), output_tuple)};
}
 
 
std::vector<simplex::Simplex> TriEdgeSwap::unmodified_primitives(
    const simplex::Simplex& simplex) const
{
    return {simplex};
}
 
} // namespace wmtk::operations::composite