example_itemspolicy.cc

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

See also:

mesht.hh

#include <mesh.hh>

#include <cstring>

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

template< class Traits >
class MyHalfedge : public a48::HalfedgeT< Traits > {
public: float thickness; 
};

template< class Traits >
class MyFace : public a48::FaceT< Traits > {
public: float color[3]; 
};

class MyTraits {
public:
    typedef MyVertex< MyTraits > vertex_type;
    typedef MyHalfedge< MyTraits > halfedge_type;
    typedef MyFace< MyTraits > face_type;
};

typedef a48::MeshT< 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;
    float *edge_thickness;
    float *face_colors;

    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 ];
        edge_thickness = new float[ 3 ];
        edge_thickness[0] = .1f; edge_thickness[1] = .2f; edge_thickness[2] = .3f;
        face_colors = new float[ 3 ];
        face_colors[0] = .8f; face_colors[1] = .2f; face_colors[2] = .2f;
        memcpy( vertices, _vertices, num_verts * 2 * sizeof(float) );
        memcpy( faces, _faces, num_faces * 3 * sizeof(unsigned int) );
    }

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

    void set_vertex_attributes(vertex_type *v1, const vertex_type *v0) {
        v1->id = v0->id;
        v1->pos[0] = v0->pos[0];
        v1->pos[1] = v0->pos[1];
    }

    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_halfedge_attributes(halfedge_type *h1, const halfedge_type *h0) {
        h1->thickness = h0->thickness;
    }

    void set_halfedge_attributes(halfedge_type *h, halfedge_type *o) {
        o->thickness -= .05f;
        h->thickness = o->thickness;
    }

    void set_halfedge_attributes(const unsigned int& i, const unsigned int& j, const unsigned int& hi, halfedge_type *h) {
        h->thickness = edge_thickness[ i+j - 1 ];
    }

    void set_face_attributes(face_type *f1, const face_type *f0) {
        f1->color[0] = f0->color[0];
        f1->color[1] = f0->color[1];
        f1->color[2] = f0->color[2];
    }

    void set_face_attributes(const unsigned int& i, face_type *f) {
        f->color[0] = face_colors[ i*3 + 0 ];
        f->color[1] = face_colors[ i*3 + 1 ];
        f->color[2] = face_colors[ i*3 + 2 ];
    }

};

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