static int CheckForRightSplice( TESStesselator *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);
TESShalfEdge *eUp = regUp->eUp;
TESShalfEdge *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 ( tessMeshSplitEdge( tess->mesh, eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, 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 );
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 */
RegionAbove(regUp)->dirty = regUp->dirty = TRUE;
if (tessMeshSplitEdge( tess->mesh, eUp->Sym ) == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eLo->Oprev, eUp ) ) longjmp(tess->env,1);
}
return TRUE;
}
static int CheckForLeftSplice( TESStesselator *tess, ActiveRegion *regUp )
/*
* Check the upper and lower edge of "regUp", to make sure that the
* eUp->Dst is above eLo, or eLo->Dst is below eUp (depending on which
* destination is rightmost).
*
* Theoretically, this should always be true. However, splitting an edge
* into two pieces can change the results of previous tests. For example,
* suppose at one point we checked eUp and eLo, and decided that eUp->Dst
* 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
* the test so that now eUp->Dst is incident to eLo, or barely below it.
* We must correct this condition to maintain the dictionary invariants
* (otherwise new edges might get inserted in the wrong place in the
* dictionary, and bad stuff will happen).
*
* We fix the problem by just splicing the offending vertex into the
* other edge.
*/
{
ActiveRegion *regLo = RegionBelow(regUp);
TESShalfEdge *eUp = regUp->eUp;
TESShalfEdge *eLo = regLo->eUp;
TESShalfEdge *e;
assert( ! VertEq( eUp->Dst, eLo->Dst ));
if( VertLeq( eUp->Dst, eLo->Dst )) {
if( EdgeSign( eUp->Dst, eLo->Dst, eUp->Org ) < 0 ) return FALSE;
/* eLo->Dst is above eUp, so splice eLo->Dst into eUp */
RegionAbove(regUp)->dirty = regUp->dirty = TRUE;
e = tessMeshSplitEdge( tess->mesh, eUp );
if (e == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eLo->Sym, e ) ) longjmp(tess->env,1);
e->Lface->inside = regUp->inside;
} else {
if( EdgeSign( eLo->Dst, eUp->Dst, eLo->Org ) > 0 ) return FALSE;
/* eUp->Dst is below eLo, so splice eUp->Dst into eLo */
regUp->dirty = regLo->dirty = TRUE;
e = tessMeshSplitEdge( tess->mesh, eLo );
if (e == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eUp->Lnext, eLo->Sym ) ) longjmp(tess->env,1);
e->Rface->inside = regUp->inside;
}
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 );
}
void tessAddContour( TESStesselator *tess, int size, const void* vertices,
int stride, int numVertices )
{
const unsigned char *src = (const unsigned char*)vertices;
TESShalfEdge *e;
int i;
if ( tess->mesh == NULL )
tess->mesh = tessMeshNewMesh( &tess->alloc );
if ( tess->mesh == NULL ) {
tess->outOfMemory = 1;
return;
}
if ( size < 2 )
size = 2;
if ( size > 3 )
size = 3;
e = NULL;
for( i = 0; i < numVertices; ++i )
{
const TESSreal* coords = (const TESSreal*)src;
src += stride;
if( e == NULL ) {
/* Make a self-loop (one vertex, one edge). */
e = tessMeshMakeEdge( tess->mesh );
if ( e == NULL ) {
tess->outOfMemory = 1;
return;
}
if ( !tessMeshSplice( tess->mesh, e, e->Sym ) ) {
tess->outOfMemory = 1;
return;
}
} else {
/* Create a new vertex and edge which immediately follow e
* in the ordering around the left face.
*/
if ( tessMeshSplitEdge( tess->mesh, e ) == NULL ) {
tess->outOfMemory = 1;
return;
}
e = e->Lnext;
}
/* The new vertex is now e->Org. */
e->Org->coords[0] = coords[0];
e->Org->coords[1] = coords[1];
if ( size > 2 )
e->Org->coords[2] = coords[2];
else
e->Org->coords[2] = 0;
/* Store the insertion number so that the vertex can be later recognized. */
e->Org->idx = tess->vertexIndexCounter++;
/* 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;
}
}
static int CheckForIntersect( TESStesselator *tess, ActiveRegion *regUp )
/*
* Check the upper and lower edges of the given region to see if
* they intersect. If so, create the intersection and add it
* to the data structures.
*
* Returns TRUE if adding the new intersection resulted in a recursive
* call to AddRightEdges(); in this case all "dirty" regions have been
* checked for intersections, and possibly regUp has been deleted.
*/
{
ActiveRegion *regLo = RegionBelow(regUp);
TESShalfEdge *eUp = regUp->eUp;
TESShalfEdge *eLo = regLo->eUp;
TESSvertex *orgUp = eUp->Org;
TESSvertex *orgLo = eLo->Org;
TESSvertex *dstUp = eUp->Dst;
TESSvertex *dstLo = eLo->Dst;
TESSreal tMinUp, tMaxLo;
TESSvertex isect, *orgMin;
TESShalfEdge *e;
assert( ! VertEq( dstLo, dstUp ));
assert( EdgeSign( dstUp, tess->event, orgUp ) <= 0 );
assert( EdgeSign( dstLo, tess->event, orgLo ) >= 0 );
assert( orgUp != tess->event && orgLo != tess->event );
assert( ! regUp->fixUpperEdge && ! regLo->fixUpperEdge );
if( orgUp == orgLo ) return FALSE; /* right endpoints are the same */
tMinUp = MIN( orgUp->t, dstUp->t );
tMaxLo = MAX( orgLo->t, dstLo->t );
if( tMinUp > tMaxLo ) return FALSE; /* t ranges do not overlap */
if( VertLeq( orgUp, orgLo )) {
if( EdgeSign( dstLo, orgUp, orgLo ) > 0 ) return FALSE;
} else {
if( EdgeSign( dstUp, orgLo, orgUp ) < 0 ) return FALSE;
}
/* At this point the edges intersect, at least marginally */
DebugEvent( tess );
tesedgeIntersect( dstUp, orgUp, dstLo, orgLo, &isect );
/* The following properties are guaranteed: */
assert( MIN( orgUp->t, dstUp->t ) <= isect.t );
assert( isect.t <= MAX( orgLo->t, dstLo->t ));
assert( MIN( dstLo->s, dstUp->s ) <= isect.s );
assert( isect.s <= MAX( orgLo->s, orgUp->s ));
if( VertLeq( &isect, tess->event )) {
/* The intersection point lies slightly to the left of the sweep line,
* so move it until it''s slightly to the right of the sweep line.
* (If we had perfect numerical precision, this would never happen
* in the first place). The easiest and safest thing to do is
* replace the intersection by tess->event.
*/
isect.s = tess->event->s;
isect.t = tess->event->t;
}
/* Similarly, if the computed intersection lies to the right of the
* rightmost origin (which should rarely happen), it can cause
* unbelievable inefficiency on sufficiently degenerate inputs.
* (If you have the test program, try running test54.d with the
* "X zoom" option turned on).
*/
orgMin = VertLeq( orgUp, orgLo ) ? orgUp : orgLo;
if( VertLeq( orgMin, &isect )) {
isect.s = orgMin->s;
isect.t = orgMin->t;
}
if( VertEq( &isect, orgUp ) || VertEq( &isect, orgLo )) {
/* Easy case -- intersection at one of the right endpoints */
(void) CheckForRightSplice( tess, regUp );
return FALSE;
}
if( (! VertEq( dstUp, tess->event )
&& EdgeSign( dstUp, tess->event, &isect ) >= 0)
|| (! VertEq( dstLo, tess->event )
&& EdgeSign( dstLo, tess->event, &isect ) <= 0 ))
{
/* Very unusual -- the new upper or lower edge would pass on the
* wrong side of the sweep event, or through it. This can happen
* due to very small numerical errors in the intersection calculation.
*/
if( dstLo == tess->event ) {
/* Splice dstLo into eUp, and process the new region(s) */
if (tessMeshSplitEdge( tess->mesh, eUp->Sym ) == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eLo->Sym, eUp ) ) longjmp(tess->env,1);
regUp = TopLeftRegion( tess, regUp );
if (regUp == NULL) longjmp(tess->env,1);
eUp = RegionBelow(regUp)->eUp;
FinishLeftRegions( tess, RegionBelow(regUp), regLo );
AddRightEdges( tess, regUp, eUp->Oprev, eUp, eUp, TRUE );
return TRUE;
}
if( dstUp == tess->event ) {
/* Splice dstUp into eLo, and process the new region(s) */
if (tessMeshSplitEdge( tess->mesh, eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eUp->Lnext, eLo->Oprev ) ) longjmp(tess->env,1);
regLo = regUp;
regUp = TopRightRegion( regUp );
e = RegionBelow(regUp)->eUp->Rprev;
regLo->eUp = eLo->Oprev;
eLo = FinishLeftRegions( tess, regLo, NULL );
AddRightEdges( tess, regUp, eLo->Onext, eUp->Rprev, e, TRUE );
return TRUE;
}
/* Special case: called from ConnectRightVertex. If either
* edge passes on the wrong side of tess->event, split it
* (and wait for ConnectRightVertex to splice it appropriately).
*/
if( EdgeSign( dstUp, tess->event, &isect ) >= 0 ) {
RegionAbove(regUp)->dirty = regUp->dirty = TRUE;
if (tessMeshSplitEdge( tess->mesh, eUp->Sym ) == NULL) longjmp(tess->env,1);
eUp->Org->s = tess->event->s;
eUp->Org->t = tess->event->t;
}
if( EdgeSign( dstLo, tess->event, &isect ) <= 0 ) {
regUp->dirty = regLo->dirty = TRUE;
if (tessMeshSplitEdge( tess->mesh, eLo->Sym ) == NULL) longjmp(tess->env,1);
eLo->Org->s = tess->event->s;
eLo->Org->t = tess->event->t;
}
/* leave the rest for ConnectRightVertex */
return FALSE;
}
/* General case -- split both edges, splice into new vertex.
* When we do the splice operation, the order of the arguments is
* arbitrary as far as correctness goes. However, when the operation
* creates a new face, the work done is proportional to the size of
* the new face. We expect the faces in the processed part of
* the mesh (ie. eUp->Lface) to be smaller than the faces in the
* unprocessed original contours (which will be eLo->Oprev->Lface).
*/
if (tessMeshSplitEdge( tess->mesh, eUp->Sym ) == NULL) longjmp(tess->env,1);
if (tessMeshSplitEdge( tess->mesh, eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !tessMeshSplice( tess->mesh, eLo->Oprev, eUp ) ) longjmp(tess->env,1);
eUp->Org->s = isect.s;
eUp->Org->t = isect.t;
eUp->Org->pqHandle = pqInsert( &tess->alloc, tess->pq, eUp->Org );
if (eUp->Org->pqHandle == INV_HANDLE) {
pqDeletePriorityQ( &tess->alloc, tess->pq );
tess->pq = NULL;
longjmp(tess->env,1);
}
GetIntersectData( tess, eUp->Org, orgUp, dstUp, orgLo, dstLo );
RegionAbove(regUp)->dirty = regUp->dirty = regLo->dirty = TRUE;
return FALSE;
}
