static void RemoveDegenerateEdges( TESStesselator *tess )
/*
* Remove zero-length edges, and contours with fewer than 3 vertices.
*/
{
TESShalfEdge *e, *eNext, *eLnext;
TESShalfEdge *eHead = &tess->mesh->eHead;
/*LINTED*/
for( e = eHead->next; e != eHead; e = eNext ) {
eNext = e->next;
eLnext = e->Lnext;
if( VertEq( e->Org, e->Dst ) && e->Lnext->Lnext != e ) {
/* Zero-length edge, contour has at least 3 edges */
SpliceMergeVertices( tess, eLnext, e ); /* deletes e->Org */
if ( !tessMeshDelete( tess->mesh, e ) ) longjmp(tess->env,1); /* e is a self-loop */
e = eLnext;
eLnext = e->Lnext;
}
if( eLnext->Lnext == e ) {
/* Degenerate contour (one or two edges) */
if( eLnext != e ) {
if( eLnext == eNext || eLnext == eNext->Sym ) { eNext = eNext->next; }
if ( !tessMeshDelete( tess->mesh, eLnext ) ) longjmp(tess->env,1);
}
if( e == eNext || e == eNext->Sym ) { eNext = eNext->next; }
if ( !tessMeshDelete( tess->mesh, e ) ) longjmp(tess->env,1);
}
}
}
static int CheckForRightSplice( GLUtesselator *tess, ActiveRegion *regUp )
/*
* Check the upper and lower edge of "regUp", to make sure that the
* eUp->Org is above eLo, or eLo->Org is below eUp (depending on which
* origin is leftmost).
*
* The main purpose is to splice right-going edges with the same
* dest vertex and nearly identical slopes (ie. we can't distinguish
* the slopes numerically). However the splicing can also help us
* to recover from numerical errors. For example, suppose at one
* point we checked eUp and eLo, and decided that eUp->Org is barely
* above eLo. Then later, we split eLo into two edges (eg. from
* a splice operation like this one). This can change the result of
* our test so that now eUp->Org is incident to eLo, or barely below it.
* We must correct this condition to maintain the dictionary invariants.
*
* One possibility is to check these edges for intersection again
* (ie. CheckForIntersect). This is what we do if possible. However
* CheckForIntersect requires that tess->event lies between eUp and eLo,
* so that it has something to fall back on when the intersection
* calculation gives us an unusable answer. So, for those cases where
* we can't check for intersection, this routine fixes the problem
* by just splicing the offending vertex into the other edge.
* This is a guaranteed solution, no matter how degenerate things get.
* Basically this is a combinatorial solution to a numerical problem.
*/
{
ActiveRegion *regLo = RegionBelow(regUp);
GLUhalfEdge *eUp = regUp->eUp;
GLUhalfEdge *eLo = regLo->eUp;
if( VertLeq( eUp->Org, eLo->Org )) {
if( EdgeSign( eLo->Dst, eUp->Org, eLo->Org ) > 0 ) return FALSE;
/* eUp->Org appears to be below eLo */
if( ! VertEq( eUp->Org, eLo->Org )) {
/* Splice eUp->Org into eLo */
if ( __gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( eUp, eLo->Oprev ) ) longjmp(tess->env,1);
regUp->dirty = regLo->dirty = TRUE;
} else if( eUp->Org != eLo->Org ) {
/* merge the two vertices, discarding eUp->Org */
pqDelete( tess->pq, eUp->Org->pqHandle ); /* __gl_pqSortDelete */
SpliceMergeVertices( tess, eLo->Oprev, eUp );
}
} else {
if( EdgeSign( eUp->Dst, eLo->Org, eUp->Org ) < 0 ) return FALSE;
/* eLo->Org appears to be above eUp, so splice eLo->Org into eUp */
regUp->dirty = TRUE;
void* valid_ptr_check = RegionAbove(regUp);//->dirty
if ( valid_ptr_check ) {
RegionAbove(regUp)->dirty = TRUE;
}
if (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( eLo->Oprev, eUp ) ) longjmp(tess->env,1);
}
return TRUE;
}
static void ConnectLeftDegenerate( TESStesselator *tess,
ActiveRegion *regUp, TESSvertex *vEvent )
/*
* The event vertex lies exacty on an already-processed edge or vertex.
* Adding the new vertex involves splicing it into the already-processed
* part of the mesh.
*/
{
TESShalfEdge *e, *eTopLeft, *eTopRight, *eLast;
ActiveRegion *reg;
e = regUp->eUp;
if( VertEq( e->Org, vEvent )) {
/* e->Org is an unprocessed vertex - just combine them, and wait
* for e->Org to be pulled from the queue
*/
assert( TOLERANCE_NONZERO );
SpliceMergeVertices( tess, e, vEvent->anEdge );
return;
}
if( ! VertEq( e->Dst, vEvent )) {
/* General case -- splice vEvent into edge e which passes through it */
if (tessMeshSplitEdge( tess->mesh, e->Sym ) == NULL) longjmp(tess->env,1);
if( regUp->fixUpperEdge ) {
/* This edge was fixable -- delete unused portion of original edge */
if ( !tessMeshDelete( tess->mesh, e->Onext ) ) longjmp(tess->env,1);
regUp->fixUpperEdge = FALSE;
}
if ( !tessMeshSplice( tess->mesh, vEvent->anEdge, e ) ) longjmp(tess->env,1);
SweepEvent( tess, vEvent ); /* recurse */
return;
}
/* vEvent coincides with e->Dst, which has already been processed.
* Splice in the additional right-going edges.
*/
assert( TOLERANCE_NONZERO );
regUp = TopRightRegion( regUp );
reg = RegionBelow( regUp );
eTopRight = reg->eUp->Sym;
eTopLeft = eLast = eTopRight->Onext;
if( reg->fixUpperEdge ) {
/* Here e->Dst has only a single fixable edge going right.
* We can delete it since now we have some real right-going edges.
*/
assert( eTopLeft != eTopRight ); /* there are some left edges too */
DeleteRegion( tess, reg );
if ( !tessMeshDelete( tess->mesh, eTopRight ) ) longjmp(tess->env,1);
eTopRight = eTopLeft->Oprev;
}
if ( !tessMeshSplice( tess->mesh, vEvent->anEdge, eTopRight ) ) longjmp(tess->env,1);
if( ! EdgeGoesLeft( eTopLeft )) {
/* e->Dst had no left-going edges -- indicate this to AddRightEdges() */
eTopLeft = NULL;
}
AddRightEdges( tess, regUp, eTopRight->Onext, eLast, eTopLeft, TRUE );
}
int tessComputeInterior( TESStesselator *tess )
/*
* tessComputeInterior( tess ) computes the planar arrangement specified
* by the given contours, and further subdivides this arrangement
* into regions. Each region is marked "inside" if it belongs
* to the polygon, according to the rule given by tess->windingRule.
* Each interior region is guaranteed be monotone.
*/
{
TESSvertex *v, *vNext;
/* Each vertex defines an event for our sweep line. Start by inserting
* all the vertices in a priority queue. Events are processed in
* lexicographic order, ie.
*
* e1 < e2 iff e1.x < e2.x || (e1.x == e2.x && e1.y < e2.y)
*/
RemoveDegenerateEdges( tess );
if ( !InitPriorityQ( tess ) ) return 0; /* if error */
InitEdgeDict( tess );
while( (v = (TESSvertex *)pqExtractMin( tess->pq )) != NULL ) {
for( ;; ) {
vNext = (TESSvertex *)pqMinimum( tess->pq );
if( vNext == NULL || ! VertEq( vNext, v )) break;
/* Merge together all vertices at exactly the same location.
* This is more efficient than processing them one at a time,
* simplifies the code (see ConnectLeftDegenerate), and is also
* important for correct handling of certain degenerate cases.
* For example, suppose there are two identical edges A and B
* that belong to different contours (so without this code they would
* be processed by separate sweep events). Suppose another edge C
* crosses A and B from above. When A is processed, we split it
* at its intersection point with C. However this also splits C,
* so when we insert B we may compute a slightly different
* intersection point. This might leave two edges with a small
* gap between them. This kind of error is especially obvious
* when using boundary extraction (TESS_BOUNDARY_ONLY).
*/
vNext = (TESSvertex *)pqExtractMin( tess->pq );
SpliceMergeVertices( tess, v->anEdge, vNext->anEdge );
}
SweepEvent( tess, v );
}
/* Set tess->event for debugging purposes */
tess->event = ((ActiveRegion *) dictKey( dictMin( tess->dict )))->eUp->Org;
DebugEvent( tess );
DoneEdgeDict( tess );
DonePriorityQ( tess );
if ( !RemoveDegenerateFaces( tess, tess->mesh ) ) return 0;
tessMeshCheckMesh( tess->mesh );
return 1;
}
