example_stellarpolicy.cc

This is an example of how to use the Stellar Policy paradigm using the a48 halfedge datastructure classes.

See also:

stellarmesht.hh

#include <map>

#include <cstring>

#include <mesh.hh>

template< class Traits >
class MyVertex : public a48::VertexT< Traits > {
public: unsigned int id; float pos[2]; 
};

class MyTraits {
public:
    typedef Vertex< MyTraits > vertex_type;
    typedef a48::HalfedgeT< MyTraits > halfedge_type;
    typedef a48::FaceT< MyTraits > face_type;
};

typedef a48::StellarMeshT< MyTraits > MyMesh; 

template< class Traits >
class MyItemsPolicy : public virtual a48::BaseItemsPolicy< Traits > {

    typedef typename Traits::vertex_type vertex_type;
    typedef typename Traits::halfedge_type halfedge_type;
    typedef typename Traits::face_type face_type;

public:

    unsigned int num_verts, num_faces;
    float *vertices;
    unsigned int *faces;

    MyItemsPolicy() {
        num_verts = 3; num_faces = 1;
        const float _vertices[] = { 0.f, 0.f,  1.f, 0.f,  1.f, 1.f };
        const unsigned int _faces[] = { 0, 1, 2 };
        vertices = new float[ num_verts * 2 ];
        faces = new unsigned int[ num_faces * 3 ];
        memcpy( vertices, _vertices, num_verts * 2 * sizeof(float) );
        memcpy( faces, _faces, num_faces * 3 * sizeof(unsigned int) );
    }

    ~MyItemsPolicy() {
        delete [] vertices;
        delete [] faces;
    }

    void set_vertex_attributes(const unsigned int& i, vertex_type *v) {
        v->id = i;
        v->pos[0] = vertices[ i*2 + 0 ];
        v->pos[1] = vertices[ i*2 + 1 ];
    }

    void set_vertex_attributes(vertex_type *v1, const vertex_type *v0) { }
    void set_halfedge_attributes(halfedge_type *h1, const halfedge_type *h0) { }
    void set_halfedge_attributes(halfedge_type *h, halfedge_type *o) { }
    void set_halfedge_attributes(const unsigned int& i, const unsigned int& j, const unsigned int& hi, halfedge_type *h) { }
    void set_face_attributes(face_type *f1, const face_type *f0) { }
    void set_face_attributes(const unsigned int& i, face_type *f) { }

};

template< class Traits >
class MyStellarPolicy : public virtual a48::BaseStellarPolicy< Traits > {

    typedef typename Traits::vertex_type vertex_type;
    typedef typename Traits::halfedge_type halfedge_type;
    typedef typename Traits::face_type face_type;

    typedef std::pair< uint, uint > edge_pair;
    typedef std::map< edge_pair, vertex_type > edge_map;

public:

    edge_map emap; 

    void sample_vertex(const face_type *f, vertex_type *v) {
        sample_vertex( f->halfedge(), v );
        sample_vertex( f->halfedge()->next(), v );
        sample_vertex( f->halfedge()->previous(), v );
    }

    void sample_vertex(const halfedge_type *h, vertex_type *v) {
        uint id0 = h->vertex()->id;
        uint id1 = h->previous()->vertex()->id;
        if( id1 < id0 ) { uint idt = id0; id0 = id1; id1 = idt; }
        edge_pair e( id0, id1 );
        if( emap.find( e ) != emap.end() ) {
            v->id = emap[e].id;
            v->pos = emap[e].pos;
        }
    }

    void remove_vertex(const face_type *f, const vertex_type *v) {
        remove_vertex( f->halfedge(), v );
    }

    void remove_vertex(const halfedge_type *h, const vertex_type *v) {
        uint id0 = h->next()->opposite()->next()->vertex()->id;
        uint id1 = h->previous()->vertex()->id;
        if( id1 < id0 ) { uint idt = id0; id0 = id1; id1 = idt; }
        edge_pair e( id0, id1 );
        emap[e] = *v;
    }

    void flip_halfedge(const halfedge_type *h) {
        uint id0 = h->vertex()->id;
        uint id1 = h->previous()->vertex()->id;
        if( id1 < id0 ) { uint idt = id0; id0 = id1; id1 = idt; }
        edge_pair e( id0, id1 );
        if( emap.find( e ) != emap.end() ) {
            id0 = h->next()->vertex()->id;
            id1 = h->opposite()->next()->vertex()->id;
            if( id1 < id0 ) { uint idt = id0; id0 = id1; id1 = idt; }
            edge_pair ne( id0, id1 );
            emap[ne] = emap[e];
            emap.erase(e);
        }
    }

};

void example(void) {
    MyItemsPolicy< MyTraits > ip;
    MyStellarPolicy< MyTraits > sp;
    MyMesh m( &ip, &sp );
    m.set_base( ip.num_verts, ip.num_faces, ip.faces );
}