static void AddSentinel( GLUtesselator *tess, GLdouble t )
/*
* We add two sentinel edges above and below all other edges,
* to avoid special cases at the top and bottom.
*/
{
GLUhalfEdge *e;
ActiveRegion *reg = (ActiveRegion *)memAlloc( sizeof( ActiveRegion ));
if (reg == NULL) longjmp(tess->env,1);
e = __gl_meshMakeEdge( tess->mesh );
if (e == NULL) longjmp(tess->env,1);
e->Org->s = SENTINEL_COORD;
e->Org->t = t;
e->Dst->s = -SENTINEL_COORD;
e->Dst->t = t;
tess->event = e->Dst; /* initialize it */
reg->eUp = e;
reg->windingNumber = 0;
reg->inside = FALSE;
reg->fixUpperEdge = FALSE;
reg->sentinel = TRUE;
reg->dirty = FALSE;
reg->nodeUp = dictInsert( tess->dict, reg ); /* __gl_dictListInsertBefore */
if (reg->nodeUp == NULL) longjmp(tess->env,1);
}
static int AddVertex(GLUtesselator* tess, GLfloat coords[3], void* data)
{
GLUhalfEdge* e=NULL;
e=tess->lastEdge;
if (e==NULL)
{
/* Make a self-loop (one vertex, one edge). */
e=__gl_meshMakeEdge(tess->mesh);
if (e==NULL)
{
return 0;
}
if (!__gl_meshSplice(e, e->Sym))
{
return 0;
}
}
else
{
/* Create a new vertex and edge which immediately follow e
* in the ordering around the left face.
*/
if (__gl_meshSplitEdge(e)==NULL)
{
return 0;
}
e=e->Lnext;
}
/* The new vertex is now e->Org. */
e->Org->data=data;
e->Org->coords[0]=coords[0];
e->Org->coords[1]=coords[1];
e->Org->coords[2]=coords[2];
/* The winding of an edge says how the winding number changes as we
* cross from the edge''s right face to its left face. We add the
* vertices in such an order that a CCW contour will add +1 to
* the winding number of the region inside the contour.
*/
e->winding=1;
e->Sym->winding=-1;
tess->lastEdge=e;
return 1;
}