MRLaplacian.h

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#pragma once
 
#include "MRBitSet.h"
#include "MRVector.h"
#include "MRVector3.h"
#include "MRMeshTriPoint.h"
#include "MREnums.h"
 
namespace MR
{
 

class Laplacian
{
public:
    MRMESH_API explicit Laplacian( Mesh & mesh );
    MRMESH_API Laplacian( const MeshTopology & topology, VertCoords & points );
    MRMESH_API Laplacian( Laplacian && ) noexcept;
    MRMESH_API ~Laplacian();

    void init( const VertBitSet & freeVerts, EdgeWeights weights, VertexMass vmass = VertexMass::Unit, RememberShape rem = RememberShape::Yes )
        { initFromPoints( points_, freeVerts, weights, vmass, rem ); }

    MRMESH_API void initFromPoints( const VertCoords & points, const VertBitSet & freeVerts, EdgeWeights weights,
        VertexMass vmass = VertexMass::Unit, RememberShape rem = RememberShape::Yes );

    MRMESH_API void fixVertex( VertId v, bool smooth = true );

    MRMESH_API void fixVertex( VertId v, const Vector3f & fixedPos, bool smooth = true );

    MRMESH_API void multVertexWeight( VertId v, double factor );

    MRMESH_API void updateSolver();

    MRMESH_API void applyToVector( VertCoords & points );

    void apply() { applyToVector( points_ ); }

    MRMESH_API void applyToScalar( VertScalars & scalarField );

    [[nodiscard]] const VertBitSet & region() const { return region_; }

    [[nodiscard]] const VertBitSet & freeVerts() const { return freeVerts_; }

    [[nodiscard]] const VertBitSet & firstLayerFixedVerts() const { assert( solver_ ); return firstLayerFixedVerts_; }

    [[nodiscard]] const MeshTopology & topology() const { return topology_; }

    [[nodiscard]] VertCoords & points() const { return points_; }

    struct Attractor
    {
        MeshTriPoint p;
        Vector3d target;
        double weight = 1;
    };

    MRMESH_API void addAttractor( const Attractor& a );

    MRMESH_API void removeAllAttractors();
 
private:
    template <typename I, typename G, typename S, typename P>
    void prepareRhs_( I && iniRhs, G && g, S && s, P && p ) const;
 
    const MeshTopology & topology_;
    VertCoords & points_;

    VertBitSet region_;

    VertBitSet freeVerts_;

    VertBitSet fixedSharpVertices_;

    VertBitSet firstLayerFixedVerts_;

    struct Equation
    {
        Vector3d rhs;           
        double centerCoeff = 0; 
        int firstElem = 0;      
    };
    std::vector<Equation> equations_;
 
    std::vector<Attractor> attractors_;
 
    struct Element
    {
        double coeff = 0;
        VertId neiVert;
    };
    std::vector<Element> nonZeroElements_;

    Vector< int, VertId > regionVert2id_;
    Vector< int, VertId > freeVert2id_;
 
    class Solver;
    std::unique_ptr<Solver> solver_;
};
 
}