static struct FaceCount MaximumFan(GLUhalfEdge* eOrig)
{
/* eOrig->Lface is the face we want to render. We want to find the size
* of a maximal fan around eOrig->Org. To do this we just walk around
* the origin vertex as far as possible in both directions.
*/
struct FaceCount newFace={0, NULL, &RenderFan};
GLUface* trail=NULL;
GLUhalfEdge* e;
for (e=eOrig; !Marked(e->Lface); e=e->Onext)
{
AddToTrail(e->Lface, trail);
++newFace.size;
}
for (e=eOrig; !Marked(e->Rface); e=e->Oprev)
{
AddToTrail( e->Rface, trail);
++newFace.size;
}
newFace.eStart=e;
/*LINTED*/
FreeTrail(trail);
return newFace;
}
static struct FaceCount MaximumStrip( GLUhalfEdge *eOrig )
{
/* Here we are looking for a maximal strip that contains the vertices
* eOrig->Org, eOrig->Dst, eOrig->Lnext->Dst (in that order or the
* reverse, such that all triangles are oriented CCW).
*
* Again we walk forward and backward as far as possible. However for
* strips there is a twist: to get CCW orientations, there must be
* an *even* number of triangles in the strip on one side of eOrig.
* We walk the strip starting on a side with an even number of triangles;
* if both side have an odd number, we are forced to shorten one side.
*/
struct FaceCount newFace = { 0, NULL, &RenderStrip };
long headSize = 0, tailSize = 0;
GLUface *trail = NULL;
GLUhalfEdge *e, *eTail, *eHead;
for( e = eOrig; ! Marked( e->Lface ); ++tailSize, e = e->Onext ) {
AddToTrail( e->Lface, trail );
++tailSize;
e = e->Dprev;
if( Marked( e->Lface )) break;
AddToTrail( e->Lface, trail );
}
eTail = e;
for( e = eOrig; ! Marked( e->Rface ); ++headSize, e = e->Dnext ) {
AddToTrail( e->Rface, trail );
++headSize;
e = e->Oprev;
if( Marked( e->Rface )) break;
AddToTrail( e->Rface, trail );
}
eHead = e;
newFace.size = tailSize + headSize;
if( IsEven( tailSize )) {
newFace.eStart = eTail->Sym;
} else if( IsEven( headSize )) {
newFace.eStart = eHead;
} else {
/* Both sides have odd length, we must shorten one of them. In fact,
* we must start from eHead to guarantee inclusion of eOrig->Lface.
*/
--newFace.size;
newFace.eStart = eHead->Onext;
}
/*LINTED*/
FreeTrail( trail );
return newFace;
}
