// ANSWER:
// An ON_BrepEdge is connector for joining ON_BrepTrim objects and representing
// a 3-D location of the seam they form. An Edge can connect 1 or more trims.
// In the case of a simple "joined edge" there will be 2 trims, one from each
// adjacent face. In a closed face, like a cylinder, the trims will be different
// on each side of the face, and they will both be in the same loop and belong to
// the same face.
static const ON_BrepFace* GetOtherFace(const ON_BrepTrim* trim)
{
ON_BrepFace* face = 0;
if (0 == trim)
return 0;
ON_Brep* brep = trim->Brep();
if (0 == brep)
return 0;
const ON_BrepEdge* edge = trim->Edge();
if (0 == edge)
return 0;
// Trim count on a proper joined edge should be 2.
const int trim_count = edge->TrimCount();
if (trim_count < 2)
return 0; // Not joined
if (trim_count > 2)
return 0; // Joined to more than one other surface (non-manifold)
for (int i = 0; i < trim_count; i++)
{
// Look for a trim that's not the same as the input one
// edge->m_ti is an array of indexes of the trims connected to an edge
const ON_BrepTrim* other_trim = brep->Trim(edge->m_ti[i]);
if (0 != other_trim && trim != other_trim)
{
// There is another trim on the edge, and its not the same as the input one.
// So get the face it belonge to.
face = other_trim->Face();
// You can also get the loop on the other side of the edge
//const ON_BrepLoop* other_loop = other_trim->Loop();
// Or the surface geometry of the face
//const ON_Surface* srf = face->SurfaceOf();
break;
}
}
return face;
}
static
bool ChangeTrimBdryToSing( ON_Brep& brep, ON_BrepTrim& trim,
ON_BrepTrim* prevtrim, ON_BrepTrim* nexttrim )
{
if ( trim.m_vi[0] == trim.m_vi[1] )
return false;
if ( trim.m_type == ON_BrepTrim::singular )
return false;
if ( trim.m_ei < 0 )
return false;
int vi0 = trim.m_vi[0];
int vi1 = trim.m_vi[1];
int sing_vi = vi0;
ON_BrepVertex* v0 = brep.Vertex(vi0);
if ( v0 )
v0->m_tolerance = ON_UNSET_VALUE;
ON_BrepVertex* v1 = brep.Vertex(vi1);
if ( v1 )
v1->m_tolerance = ON_UNSET_VALUE;
ON_BrepEdge* edge = brep.Edge(trim.m_ei);
if ( edge )
{
for ( int eti = 0; eti < edge->m_ti.Count(); eti++ )
{
if ( edge->m_ti[eti] == trim.m_trim_index )
{
edge->m_ti.Remove(eti);
break;
}
}
trim.m_ei = -1;
if ( 0 == edge->m_ti.Count() )
{
brep.DeleteEdge( *edge, true );
}
else if ( 1 == edge->m_ti.Count() && ON_BrepTrim::seam == trim.m_type )
{
// change neighbor trim type
ON_BrepTrim* other_trim = brep.Trim(edge->m_ti[0]);
if ( 0 != other_trim && ON_BrepTrim::seam == other_trim->m_type )
{
other_trim->m_type = ON_BrepTrim::boundary;
int j = (trim.m_bRev3d == other_trim->m_bRev3d) ? 0 : 1;
if ( trim.m_vi[0] == other_trim->m_vi[j]
&& trim.m_vi[1] == other_trim->m_vi[1-j] )
{
// we need a new singular vertex
sing_vi = brep.NewVertex(ON_UNSET_POINT).m_vertex_index;
}
}
}
}
trim.m_vi[0] = sing_vi;
trim.m_vi[1] = sing_vi;
trim.m_type = ON_BrepTrim::singular;
trim.m_bRev3d = false;
if ( nexttrim )
ChangeTrimVertex( brep,*nexttrim,0,vi1,sing_vi,true,true);
if ( prevtrim )
ChangeTrimVertex( brep,*prevtrim,1,vi0,sing_vi,true,true);
return true;
}
static
bool ChangeEdgeVertex(
ON_Brep& brep,
ON_BrepEdge& edge,
int edge_end,
int old_vi,
int new_vi,
bool bUpdateTrims
)
{
// used by ON_Brep::ReplaceSurface() to change edge ends
if ( edge_end != 0 && edge_end != 1 )
return false;
if ( edge.m_vi[edge_end] != old_vi )
return false;
if ( old_vi == new_vi )
return true;
ON_BrepVertex* old_v = brep.Vertex(old_vi);
if ( old_vi >= 0 && 0 == old_v )
return false;
if ( old_v )
old_v->m_tolerance = ON_UNSET_VALUE;
ON_BrepVertex* new_v = brep.Vertex(new_vi);
if ( new_vi >= 0 && 0 == new_v )
return false;
if ( new_v )
old_v->m_tolerance = ON_UNSET_VALUE;
// disconnect edge from old vertex
if ( old_vi >= 0 )
{
for ( int vei = 0; vei < old_v->m_ei.Count(); vei++ )
{
if ( old_v->m_ei[vei] == edge.m_edge_index )
{
old_v->m_ei.Remove(vei);
break;
}
}
}
edge.m_vi[edge_end] = new_vi;
new_v->m_ei.Append(edge.m_edge_index);
if ( bUpdateTrims )
{
for ( int eti = 0; eti < edge.m_ti.Count(); eti++ )
{
ON_BrepTrim* trim = brep.Trim(edge.m_ti[eti]);
if ( 0 == trim )
continue;
int trim_end = trim->m_bRev3d ? 1-edge_end : edge_end;
if ( trim->m_vi[trim_end] == old_vi )
trim->m_vi[trim_end] = new_vi;
}
}
return true;
}