MESHLIB

a halfedge-based mesh library for 3d-mesh

You can find the core library in the /MeshLib, and demo in the /MyDemo; some mesh data for testing is in the /Data. /MyDemo/main.cpp shows how to use this library. in /MyDemo/MyMesh.h, there are some namespaces that implement some algrithoms.

SOME TIPS FOR USING

WHAT SHOULD BE DONE WHILE BUILDING A MESH

1. label boundary for edges, halfedges, vertex

//Label boundary edges
for( typename std::list<CEdge*>::iterator eiter= m_edges.begin() ; eiter != m_edges.end() ; ++ eiter )
{
	CEdge *     edge = *eiter;
	CHalfEdge * he[2];

	he[0] = edgeHalfedge( edge, 0 );
	he[1] = edgeHalfedge( edge, 1 );
	
	assert( he[0] != NULL );
	

	if( he[1] != NULL )
	{
		assert( he[0]->target() == he[1]->source() && he[0]->source() == he[1]->target() );

		if( he[0]->target()->id() < he[0]->source()->id() )
		{
			edge->halfedge(0 ) = he[1];
			edge->halfedge(1 ) = he[0];
		}

		assert( edgeVertex1(edge)->id() < edgeVertex2(edge)->id() );
	}
	else
	{
		he[0]->vertex()->boundary() = true;
		he[0]->he_prev()->vertex()->boundary()  = true;
	}

}

2.remove the dangling vertexs

typename std::list<CVertex*> dangling_vert;
for(typename std::list<CVertex*>::iterator viter = m_verts.begin();  viter != m_verts.end() ; ++ viter )
{
	CVertex *     v = *viter;
	if( v->halfedge() != NULL ) continue;
	dangling_verts.push_back( v );
}

for( typename std::list<CVertex*>::iterator  viter = dangling_verts.begin() ; viter != dangling_verts.end(); ++ viter )
{
	CVertex * v = *viter;
	m_verts.remove( v );
	delete v;
	v = NULL;
}

3.Arrange the boundary half_edge

//Arrange the boundary half_edge of boundary vertices, to make its halfedge //to be the most ccw in half_edge

for(typename std::list<CVertex*>::iterator viter = m_verts.begin();  viter != m_verts.end() ; ++ viter )
{
	CVertex *     v = *viter;
	if( !v->boundary() ) continue;

	CHalfEdge * he = vertexMostCcwInHalfEdge( v );
	while( he->he_sym() != NULL )
	{
		he =  vertexNextCcwInHalfEdge ( he );
	}
	v->halfedge() = he;
}

WHAT SHOULD BE DONE WHILE CREATING NEW FACES

1. create new face and push it into m_faces, insert a pair <id, face> into m_map_face

CFace * f = new CFace();
assert( f != NULL );
f->id() = id;
m_faces.push_back( f );
m_map_face.insert( std::pair<int,tFace>(id,f) );

2. create new halfedges of faces, binding with vertex

//create halfedges
std::vector<tHalfEdge> hes;
for(size_t i = 0; i < v.size(); i ++ )
{
    tHalfEdge pH = new CHalfEdge;
    assert( pH );
    CVertex * vert =  v[i];
    pH->vertex() = vert;
    vert->halfedge() = pH;
    hes.push_back( pH );
}

3. linking halfeges to each other

//linking to each other
for( size_t i = 0; i < hes.size(); i ++ )
{
    hes[i]->he_next() = hes[(i+1)%hes.size()];
    hes[i]->he_prev() = hes[(i+hes.size()-1)%hes.size()];
}

4. linking halfedges to the face

//linking to face
for(size_t i = 0; i < hes.size(); i ++ )
{
    hes[i]->face()   = f;
    f->halfedge()    = hes[i];
}

5. linking halfedge to the edge

//connecting with edge
for( size_t i = 0; i < hes.size(); i ++ )
{
    tEdge e = createEdge( v[i], v[(i+hes.size()-1)%hes.size()] );
    if( e->halfedge(0)  == NULL )
    {
        e->halfedge(0) = hes[i];
    }
    else
    {
        assert( e->halfedge(1) == NULL );
        if( e->halfedge(1) != NULL )
        {
            std::cout << "Illegal Face Construction " << id << std::endl;
        }
        e->halfedge(1) = hes[i];
    }
    hes[i]->edge() = e;
}

WHAT SHOULD BE DONE WHILE CHANGING EDGE

Because the call of the method BaseMesh.h : createEdge( tVertex v1, tVertex v2 ) edges of the vertex would be searched first, if there exit a edge that link to [v1, v2], then return it.

tVertex pV = ( v1->id()id())?v1:v2; typename std::list<CEdge*> & ledges = (typename std::list<CEdge*> &) pV->edges();

for(typename std::list<CEdge*>::iterator te = ledges.begin(); te != ledges.end(); te ++ )
{
	CEdge	  * pE = *te;
	CHalfEdge * pH = (CHalfEdge*) pE->halfedge(0);

	if( pH->source() == v1 && pH->target() == v2 ) 
	{
		return pE;		
	}
	if( pH->source() == v2 && pH->target() == v1 )
	{
		return pE;
	}
}

else, create a new edge and push it into the list of pV(v1 or v2)

//new edge
CEdge * e = new CEdge;
assert( e != NULL );
m_edges.push_back( e );
e->id() = (int)m_edges.size();
ledges.push_back( e );

removing a edge

CVertex *oldv1 = oldhe1->vertex(),
        *oldv2 = oldhe2->vertex();
std::list<CEdge*> & oldledges1 = oldv1->edges();
std::list<CEdge*>::iterator it =  std::find(oldledges1.begin(), oldledges1.end(), e);
if (it != oldledges1.end()) {
    // std::cout << "erase!" << "\n";
    oldledges1.erase(it);
}

std::list<CEdge*> & oldledges2 = oldv2->edges();
it =  std::find(oldledges2.begin(), oldledges2.end(), e);
if (it != oldledges2.end()) {
    // std::cout << "erase!" << "\n";
    oldledges2.erase(it);
}

adding a new edge

CVertex* pV = (v1->id() < v2->id()) ? v1 : v2;
std::list<CEdge*> & ledges = pV->edges();
ledges.push_back(olded);