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mfem/mesh/triangle.hpp
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// Copyright (c) 2010-2025, Lawrence Livermore National Security, LLC. Produced
// at the Lawrence Livermore National Laboratory. All Rights reserved. See files
// LICENSE and NOTICE for details. LLNL-CODE-806117.
//
// This file is part of the MFEM library. For more information and source code
// availability visit https://mfem.org.
//
// MFEM is free software; you can redistribute it and/or modify it under the
// terms of the BSD-3 license. We welcome feedback and contributions, see file
// CONTRIBUTING.md for details.
#ifndef MFEM_TRIANGLE
#define MFEM_TRIANGLE
#include "../config/config.hpp"
#include "../fem/fe.hpp"
#include "element.hpp"
namespace mfem
{
/// Data type triangle element
class Triangle : public Element
{
protected:
int indices[3];
unsigned transform;
public:
typedef Geometry::Constants<Geometry::TRIANGLE> geom_t;
Triangle() : Element(Geometry::TRIANGLE) { transform = 0; }
/// Constructs triangle by specifying the indices and the attribute.
Triangle(const int *ind, int attr = 1);
/// Constructs triangle by specifying the indices and the attribute.
Triangle(int ind1, int ind2, int ind3, int attr = 1);
/// Return element's type.
Type GetType() const override { return Element::TRIANGLE; }
/// Return 1 if the element needs refinement in order to get conforming mesh.
int NeedRefinement(HashTable<Hashed2> &v_to_v) const override;
/** Reorder the vertices so that the longest edge is from vertex 0
to vertex 1. If called it should be once from the mesh constructor,
because the order may be used later for setting the edges. **/
void MarkEdge(DenseMatrix & pmat);
static void MarkEdge(int *indices, const DSTable &v_to_v, const int *length);
/// Mark the longest edge by assuming/changing the order of the vertices.
void MarkEdge(const DSTable &v_to_v, const int *length) override
{ MarkEdge(indices, v_to_v, length); }
void ResetTransform(int tr) override { transform = tr; }
unsigned GetTransform() const override { return transform; }
/// Add 'tr' to the current chain of coarse-fine transformations.
void PushTransform(int tr) override
{ transform = (transform << 3) | (tr + 1); }
/// Calculate point matrix corresponding to a chain of transformations.
static void GetPointMatrix(unsigned transform, DenseMatrix &pm);
/// Get the indices defining the vertices.
void GetVertices(Array<int> &v) const override;
/// Set the indices defining the vertices.
void SetVertices(const Array<int> &v) override;
/// @note The returned array should NOT be deleted by the caller.
int * GetVertices () override { return indices; }
/// Set the indices defining the vertices.
void SetVertices(const int *ind) override;
int GetNVertices() const override { return 3; }
int GetNEdges() const override { return (3); }
const int *GetEdgeVertices(int ei) const override
{ return geom_t::Edges[ei]; }
/// @deprecated Use GetNFaces(void) and GetNFaceVertices(int) instead.
MFEM_DEPRECATED int GetNFaces(int &nFaceVertices) const override
{ nFaceVertices = 0; return 0; }
int GetNFaces() const override { return 0; }
int GetNFaceVertices(int) const override { return 0; }
const int *GetFaceVertices(int fi) const override
{ MFEM_ABORT("not implemented"); return NULL; }
Element *Duplicate(Mesh *m) const override
{ return new Triangle(indices, attribute); }
virtual ~Triangle() = default;
};
// Defined in fe.cpp to ensure construction before 'mfem::Geometries'.
extern MFEM_EXPORT Linear2DFiniteElement TriangleFE;
}
#endif