/*
* SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
* Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice including the dates of first publication and
* either this permission notice or a reference to
* http://oss.sgi.com/projects/FreeB/
* shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* SILICON GRAPHICS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
* OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Except as contained in this notice, the name of Silicon Graphics, Inc.
* shall not be used in advertising or otherwise to promote the sale, use or
* other dealings in this Software without prior written authorization from
* Silicon Graphics, Inc.
*/
/*
** Author: Eric Veach, July 1994.
**
*/
#include "gluos.h"
#include
#include
#include /* longjmp */
#include /* LONG_MAX */
#include "mesh.h"
#include "geom.h"
#include "tess.h"
#include "dict.h"
#include "priorityq.h"
#include "memalloc.h"
#include "sweep.h"
#define TRUE 1
#define FALSE 0
#ifdef FOR_TRITE_TEST_PROGRAM
extern void DebugEvent( GLUtesselator *tess );
#else
#define DebugEvent( tess )
#endif
/*
* Invariants for the Edge Dictionary.
* - each pair of adjacent edges e2=Succ(e1) satisfies EdgeLeq(e1,e2)
* at any valid location of the sweep event
* - if EdgeLeq(e2,e1) as well (at any valid sweep event), then e1 and e2
* share a common endpoint
* - for each e, e->Dst has been processed, but not e->Org
* - each edge e satisfies VertLeq(e->Dst,event) && VertLeq(event,e->Org)
* where "event" is the current sweep line event.
* - no edge e has zero length
*
* Invariants for the Mesh (the processed portion).
* - the portion of the mesh left of the sweep line is a planar graph,
* ie. there is *some* way to embed it in the plane
* - no processed edge has zero length
* - no two processed vertices have identical coordinates
* - each "inside" region is monotone, ie. can be broken into two chains
* of monotonically increasing vertices according to VertLeq(v1,v2)
* - a non-invariant: these chains may intersect (very slightly)
*
* Invariants for the Sweep.
* - if none of the edges incident to the event vertex have an activeRegion
* (ie. none of these edges are in the edge dictionary), then the vertex
* has only right-going edges.
* - if an edge is marked "fixUpperEdge" (it is a temporary edge introduced
* by ConnectRightVertex), then it is the only right-going edge from
* its associated vertex. (This says that these edges exist only
* when it is necessary.)
*/
#undef MAX
#undef MIN
#define MAX(x,y) ((x) >= (y) ? (x) : (y))
#define MIN(x,y) ((x) <= (y) ? (x) : (y))
/* When we merge two edges into one, we need to compute the combined
* winding of the new edge.
*/
#define AddWinding(eDst,eSrc) (eDst->winding += eSrc->winding, \
eDst->Sym->winding += eSrc->Sym->winding)
static void SweepEvent( GLUtesselator *tess, GLUvertex *vEvent );
static void WalkDirtyRegions( GLUtesselator *tess, ActiveRegion *regUp );
static int CheckForRightSplice( GLUtesselator *tess, ActiveRegion *regUp );
static int EdgeLeq( GLUtesselator *tess, ActiveRegion *reg1,
ActiveRegion *reg2 )
/*
* Both edges must be directed from right to left (this is the canonical
* direction for the upper edge of each region).
*
* The strategy is to evaluate a "t" value for each edge at the
* current sweep line position, given by tess->event. The calculations
* are designed to be very stable, but of course they are not perfect.
*
* Special case: if both edge destinations are at the sweep event,
* we sort the edges by slope (they would otherwise compare equally).
*/
{
GLUvertex *event = tess->event;
GLUhalfEdge *e1, *e2;
GLdouble t1, t2;
e1 = reg1->eUp;
e2 = reg2->eUp;
if( e1->Dst == event ) {
if( e2->Dst == event ) {
/* Two edges right of the sweep line which meet at the sweep event.
* Sort them by slope.
*/
if( VertLeq( e1->Org, e2->Org )) {
return EdgeSign( e2->Dst, e1->Org, e2->Org ) <= 0;
}
return EdgeSign( e1->Dst, e2->Org, e1->Org ) >= 0;
}
return EdgeSign( e2->Dst, event, e2->Org ) <= 0;
}
if( e2->Dst == event ) {
return EdgeSign( e1->Dst, event, e1->Org ) >= 0;
}
/* General case - compute signed distance *from* e1, e2 to event */
t1 = EdgeEval( e1->Dst, event, e1->Org );
t2 = EdgeEval( e2->Dst, event, e2->Org );
return (t1 >= t2);
}
static void DeleteRegion( GLUtesselator *tess, ActiveRegion *reg )
{
if( reg->fixUpperEdge ) {
/* It was created with zero winding number, so it better be
* deleted with zero winding number (ie. it better not get merged
* with a real edge).
*/
assert( reg->eUp->winding == 0 );
}
reg->eUp->activeRegion = NULL;
dictDelete( tess->dict, reg->nodeUp ); /* __gl_dictListDelete */
memFree( reg );
}
static int FixUpperEdge( ActiveRegion *reg, GLUhalfEdge *newEdge )
/*
* Replace an upper edge which needs fixing (see ConnectRightVertex).
*/
{
assert( reg->fixUpperEdge );
if ( !__gl_meshDelete( reg->eUp ) ) return 0;
reg->fixUpperEdge = FALSE;
reg->eUp = newEdge;
newEdge->activeRegion = reg;
return 1;
}
static ActiveRegion *TopLeftRegion( ActiveRegion *reg )
{
GLUvertex *org = reg->eUp->Org;
GLUhalfEdge *e;
/* Find the region above the uppermost edge with the same origin */
do {
reg = RegionAbove( reg );
} while( reg->eUp->Org == org );
/* If the edge above was a temporary edge introduced by ConnectRightVertex,
* now is the time to fix it.
*/
if( reg->fixUpperEdge ) {
e = __gl_meshConnect( RegionBelow(reg)->eUp->Sym, reg->eUp->Lnext );
if (e == NULL) return NULL;
if ( !FixUpperEdge( reg, e ) ) return NULL;
reg = RegionAbove( reg );
}
return reg;
}
static ActiveRegion *TopRightRegion( ActiveRegion *reg )
{
GLUvertex *dst = reg->eUp->Dst;
/* Find the region above the uppermost edge with the same destination */
do {
reg = RegionAbove( reg );
} while( reg->eUp->Dst == dst );
return reg;
}
static ActiveRegion *AddRegionBelow( GLUtesselator *tess,
ActiveRegion *regAbove,
GLUhalfEdge *eNewUp )
/*
* Add a new active region to the sweep line, *somewhere* below "regAbove"
* (according to where the new edge belongs in the sweep-line dictionary).
* The upper edge of the new region will be "eNewUp".
* Winding number and "inside" flag are not updated.
*/
{
ActiveRegion *regNew = (ActiveRegion *)memAlloc( sizeof( ActiveRegion ));
if (regNew == NULL) longjmp(tess->env,1);
regNew->eUp = eNewUp;
/* __gl_dictListInsertBefore */
regNew->nodeUp = dictInsertBefore( tess->dict, regAbove->nodeUp, regNew );
if (regNew->nodeUp == NULL) longjmp(tess->env,1);
regNew->fixUpperEdge = FALSE;
regNew->sentinel = FALSE;
regNew->dirty = FALSE;
eNewUp->activeRegion = regNew;
return regNew;
}
static GLboolean IsWindingInside( GLUtesselator *tess, int n )
{
switch( tess->windingRule ) {
case GLU_TESS_WINDING_ODD:
return (n & 1);
case GLU_TESS_WINDING_NONZERO:
return (n != 0);
case GLU_TESS_WINDING_POSITIVE:
return (n > 0);
case GLU_TESS_WINDING_NEGATIVE:
return (n < 0);
case GLU_TESS_WINDING_ABS_GEQ_TWO:
return (n >= 2) || (n <= -2);
}
/*LINTED*/
assert( FALSE );
/*NOTREACHED*/
return GL_FALSE; /* avoid compiler complaints */
}
static void ComputeWinding( GLUtesselator *tess, ActiveRegion *reg )
{
reg->windingNumber = RegionAbove(reg)->windingNumber + reg->eUp->winding;
reg->inside = IsWindingInside( tess, reg->windingNumber );
}
static void FinishRegion( GLUtesselator *tess, ActiveRegion *reg )
/*
* Delete a region from the sweep line. This happens when the upper
* and lower chains of a region meet (at a vertex on the sweep line).
* The "inside" flag is copied to the appropriate mesh face (we could
* not do this before -- since the structure of the mesh is always
* changing, this face may not have even existed until now).
*/
{
GLUhalfEdge *e = reg->eUp;
GLUface *f = e->Lface;
f->inside = reg->inside;
f->anEdge = e; /* optimization for __gl_meshTessellateMonoRegion() */
DeleteRegion( tess, reg );
}
static GLUhalfEdge *FinishLeftRegions( GLUtesselator *tess,
ActiveRegion *regFirst, ActiveRegion *regLast )
/*
* We are given a vertex with one or more left-going edges. All affected
* edges should be in the edge dictionary. Starting at regFirst->eUp,
* we walk down deleting all regions where both edges have the same
* origin vOrg. At the same time we copy the "inside" flag from the
* active region to the face, since at this point each face will belong
* to at most one region (this was not necessarily true until this point
* in the sweep). The walk stops at the region above regLast; if regLast
* is NULL we walk as far as possible. At the same time we relink the
* mesh if necessary, so that the ordering of edges around vOrg is the
* same as in the dictionary.
*/
{
ActiveRegion *reg, *regPrev;
GLUhalfEdge *e, *ePrev;
regPrev = regFirst;
ePrev = regFirst->eUp;
while( regPrev != regLast ) {
regPrev->fixUpperEdge = FALSE; /* placement was OK */
reg = RegionBelow( regPrev );
e = reg->eUp;
if( e->Org != ePrev->Org ) {
if( ! reg->fixUpperEdge ) {
/* Remove the last left-going edge. Even though there are no further
* edges in the dictionary with this origin, there may be further
* such edges in the mesh (if we are adding left edges to a vertex
* that has already been processed). Thus it is important to call
* FinishRegion rather than just DeleteRegion.
*/
FinishRegion( tess, regPrev );
break;
}
/* If the edge below was a temporary edge introduced by
* ConnectRightVertex, now is the time to fix it.
*/
e = __gl_meshConnect( ePrev->Lprev, e->Sym );
if (e == NULL) longjmp(tess->env,1);
if ( !FixUpperEdge( reg, e ) ) longjmp(tess->env,1);
}
/* Relink edges so that ePrev->Onext == e */
if( ePrev->Onext != e ) {
if ( !__gl_meshSplice( e->Oprev, e ) ) longjmp(tess->env,1);
if ( !__gl_meshSplice( ePrev, e ) ) longjmp(tess->env,1);
}
FinishRegion( tess, regPrev ); /* may change reg->eUp */
ePrev = reg->eUp;
regPrev = reg;
}
return ePrev;
}
static void AddRightEdges( GLUtesselator *tess, ActiveRegion *regUp,
GLUhalfEdge *eFirst, GLUhalfEdge *eLast, GLUhalfEdge *eTopLeft,
GLboolean cleanUp )
/*
* Purpose: insert right-going edges into the edge dictionary, and update
* winding numbers and mesh connectivity appropriately. All right-going
* edges share a common origin vOrg. Edges are inserted CCW starting at
* eFirst; the last edge inserted is eLast->Oprev. If vOrg has any
* left-going edges already processed, then eTopLeft must be the edge
* such that an imaginary upward vertical segment from vOrg would be
* contained between eTopLeft->Oprev and eTopLeft; otherwise eTopLeft
* should be NULL.
*/
{
ActiveRegion *reg, *regPrev;
GLUhalfEdge *e, *ePrev;
int firstTime = TRUE;
/* Insert the new right-going edges in the dictionary */
e = eFirst;
do {
assert( VertLeq( e->Org, e->Dst ));
AddRegionBelow( tess, regUp, e->Sym );
e = e->Onext;
} while ( e != eLast );
/* Walk *all* right-going edges from e->Org, in the dictionary order,
* updating the winding numbers of each region, and re-linking the mesh
* edges to match the dictionary ordering (if necessary).
*/
if( eTopLeft == NULL ) {
eTopLeft = RegionBelow( regUp )->eUp->Rprev;
}
regPrev = regUp;
ePrev = eTopLeft;
for( ;; ) {
reg = RegionBelow( regPrev );
e = reg->eUp->Sym;
if( e->Org != ePrev->Org ) break;
if( e->Onext != ePrev ) {
/* Unlink e from its current position, and relink below ePrev */
if ( !__gl_meshSplice( e->Oprev, e ) ) longjmp(tess->env,1);
if ( !__gl_meshSplice( ePrev->Oprev, e ) ) longjmp(tess->env,1);
}
/* Compute the winding number and "inside" flag for the new regions */
reg->windingNumber = regPrev->windingNumber - e->winding;
reg->inside = IsWindingInside( tess, reg->windingNumber );
/* Check for two outgoing edges with same slope -- process these
* before any intersection tests (see example in __gl_computeInterior).
*/
regPrev->dirty = TRUE;
if( ! firstTime && CheckForRightSplice( tess, regPrev )) {
AddWinding( e, ePrev );
DeleteRegion( tess, regPrev );
if ( !__gl_meshDelete( ePrev ) ) longjmp(tess->env,1);
}
firstTime = FALSE;
regPrev = reg;
ePrev = e;
}
regPrev->dirty = TRUE;
assert( regPrev->windingNumber - e->winding == reg->windingNumber );
if( cleanUp ) {
/* Check for intersections between newly adjacent edges. */
WalkDirtyRegions( tess, regPrev );
}
}
static void CallCombine( GLUtesselator *tess, GLUvertex *isect,
void *data[4], GLfloat weights[4], int needed )
{
GLdouble coords[3];
/* Copy coord data in case the callback changes it. */
coords[0] = isect->coords[0];
coords[1] = isect->coords[1];
coords[2] = isect->coords[2];
isect->data = NULL;
CALL_COMBINE_OR_COMBINE_DATA( coords, data, weights, &isect->data );
if( isect->data == NULL ) {
if( ! needed ) {
isect->data = data[0];
} else if( ! tess->fatalError ) {
/* The only way fatal error is when two edges are found to intersect,
* but the user has not provided the callback necessary to handle
* generated intersection points.
*/
CALL_ERROR_OR_ERROR_DATA( GLU_TESS_NEED_COMBINE_CALLBACK );
tess->fatalError = TRUE;
}
}
}
static void SpliceMergeVertices( GLUtesselator *tess, GLUhalfEdge *e1,
GLUhalfEdge *e2 )
/*
* Two vertices with idential coordinates are combined into one.
* e1->Org is kept, while e2->Org is discarded.
*/
{
void *data[4] = { NULL, NULL, NULL, NULL };
GLfloat weights[4] = { 0.5, 0.5, 0.0, 0.0 };
data[0] = e1->Org->data;
data[1] = e2->Org->data;
CallCombine( tess, e1->Org, data, weights, FALSE );
if ( !__gl_meshSplice( e1, e2 ) ) longjmp(tess->env,1);
}
static void VertexWeights( GLUvertex *isect, GLUvertex *org, GLUvertex *dst,
GLfloat *weights )
/*
* Find some weights which describe how the intersection vertex is
* a linear combination of "org" and "dest". Each of the two edges
* which generated "isect" is allocated 50% of the weight; each edge
* splits the weight between its org and dst according to the
* relative distance to "isect".
*/
{
GLdouble t1 = VertL1dist( org, isect );
GLdouble t2 = VertL1dist( dst, isect );
weights[0] = 0.5 * t2 / (t1 + t2);
weights[1] = 0.5 * t1 / (t1 + t2);
isect->coords[0] += weights[0]*org->coords[0] + weights[1]*dst->coords[0];
isect->coords[1] += weights[0]*org->coords[1] + weights[1]*dst->coords[1];
isect->coords[2] += weights[0]*org->coords[2] + weights[1]*dst->coords[2];
}
static void GetIntersectData( GLUtesselator *tess, GLUvertex *isect,
GLUvertex *orgUp, GLUvertex *dstUp,
GLUvertex *orgLo, GLUvertex *dstLo )
/*
* We've computed a new intersection point, now we need a "data" pointer
* from the user so that we can refer to this new vertex in the
* rendering callbacks.
*/
{
void *data[4];
GLfloat weights[4];
data[0] = orgUp->data;
data[1] = dstUp->data;
data[2] = orgLo->data;
data[3] = dstLo->data;
isect->coords[0] = isect->coords[1] = isect->coords[2] = 0;
VertexWeights( isect, orgUp, dstUp, &weights[0] );
VertexWeights( isect, orgLo, dstLo, &weights[2] );
CallCombine( tess, isect, data, weights, TRUE );
}
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 */
RegionAbove(regUp)->dirty = 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 int CheckForLeftSplice( GLUtesselator *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);
GLUhalfEdge *eUp = regUp->eUp;
GLUhalfEdge *eLo = regLo->eUp;
GLUhalfEdge *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 = __gl_meshSplitEdge( eUp );
if (e == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( 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 = __gl_meshSplitEdge( eLo );
if (e == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( eUp->Lnext, eLo->Sym ) ) longjmp(tess->env,1);
e->Rface->inside = regUp->inside;
}
return TRUE;
}
static int CheckForIntersect( GLUtesselator *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);
GLUhalfEdge *eUp = regUp->eUp;
GLUhalfEdge *eLo = regLo->eUp;
GLUvertex *orgUp = eUp->Org;
GLUvertex *orgLo = eLo->Org;
GLUvertex *dstUp = eUp->Dst;
GLUvertex *dstLo = eLo->Dst;
GLdouble tMinUp, tMaxLo;
GLUvertex isect, *orgMin;
GLUhalfEdge *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 );
__gl_edgeIntersect( 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 (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( eLo->Sym, eUp ) ) longjmp(tess->env,1);
regUp = TopLeftRegion( 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 (__gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( 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 (__gl_meshSplitEdge( 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 (__gl_meshSplitEdge( 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 (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
if (__gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
if ( !__gl_meshSplice( eLo->Oprev, eUp ) ) longjmp(tess->env,1);
eUp->Org->s = isect.s;
eUp->Org->t = isect.t;
eUp->Org->pqHandle = pqInsert( tess->pq, eUp->Org ); /* __gl_pqSortInsert */
if (eUp->Org->pqHandle == LONG_MAX) {
pqDeletePriorityQ(tess->pq); /* __gl_pqSortDeletePriorityQ */
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;
}
static void WalkDirtyRegions( GLUtesselator *tess, ActiveRegion *regUp )
/*
* When the upper or lower edge of any region changes, the region is
* marked "dirty". This routine walks through all the dirty regions
* and makes sure that the dictionary invariants are satisfied
* (see the comments at the beginning of this file). Of course
* new dirty regions can be created as we make changes to restore
* the invariants.
*/
{
ActiveRegion *regLo = RegionBelow(regUp);
GLUhalfEdge *eUp, *eLo;
for( ;; ) {
/* Find the lowest dirty region (we walk from the bottom up). */
while( regLo->dirty ) {
regUp = regLo;
regLo = RegionBelow(regLo);
}
if( ! regUp->dirty ) {
regLo = regUp;
regUp = RegionAbove( regUp );
if( regUp == NULL || ! regUp->dirty ) {
/* We've walked all the dirty regions */
return;
}
}
regUp->dirty = FALSE;
eUp = regUp->eUp;
eLo = regLo->eUp;
if( eUp->Dst != eLo->Dst ) {
/* Check that the edge ordering is obeyed at the Dst vertices. */
if( CheckForLeftSplice( tess, regUp )) {
/* If the upper or lower edge was marked fixUpperEdge, then
* we no longer need it (since these edges are needed only for
* vertices which otherwise have no right-going edges).
*/
if( regLo->fixUpperEdge ) {
DeleteRegion( tess, regLo );
if ( !__gl_meshDelete( eLo ) ) longjmp(tess->env,1);
regLo = RegionBelow( regUp );
eLo = regLo->eUp;
} else if( regUp->fixUpperEdge ) {
DeleteRegion( tess, regUp );
if ( !__gl_meshDelete( eUp ) ) longjmp(tess->env,1);
regUp = RegionAbove( regLo );
eUp = regUp->eUp;
}
}
}
if( eUp->Org != eLo->Org ) {
if( eUp->Dst != eLo->Dst
&& ! regUp->fixUpperEdge && ! regLo->fixUpperEdge
&& (eUp->Dst == tess->event || eLo->Dst == tess->event) )
{
/* When all else fails in CheckForIntersect(), it uses tess->event
* as the intersection location. To make this possible, it requires
* that tess->event lie between the upper and lower edges, and also
* that neither of these is marked fixUpperEdge (since in the worst
* case it might splice one of these edges into tess->event, and
* violate the invariant that fixable edges are the only right-going
* edge from their associated vertex).
*/
if( CheckForIntersect( tess, regUp )) {
/* WalkDirtyRegions() was called recursively; we're done */
return;
}
} else {
/* Even though we can't use CheckForIntersect(), the Org vertices
* may violate the dictionary edge ordering. Check and correct this.
*/
(void) CheckForRightSplice( tess, regUp );
}
}
if( eUp->Org == eLo->Org && eUp->Dst == eLo->Dst ) {
/* A degenerate loop consisting of only two edges -- delete it. */
AddWinding( eLo, eUp );
DeleteRegion( tess, regUp );
if ( !__gl_meshDelete( eUp ) ) longjmp(tess->env,1);
regUp = RegionAbove( regLo );
}
}
}
static void ConnectRightVertex( GLUtesselator *tess, ActiveRegion *regUp,
GLUhalfEdge *eBottomLeft )
/*
* Purpose: connect a "right" vertex vEvent (one where all edges go left)
* to the unprocessed portion of the mesh. Since there are no right-going
* edges, two regions (one above vEvent and one below) are being merged
* into one. "regUp" is the upper of these two regions.
*
* There are two reasons for doing this (adding a right-going edge):
* - if the two regions being merged are "inside", we must add an edge
* to keep them separated (the combined region would not be monotone).
* - in any case, we must leave some record of vEvent in the dictionary,
* so that we can merge vEvent with features that we have not seen yet.
* For example, maybe there is a vertical edge which passes just to
* the right of vEvent; we would like to splice vEvent into this edge.
*
* However, we don't want to connect vEvent to just any vertex. We don''t
* want the new edge to cross any other edges; otherwise we will create
* intersection vertices even when the input data had no self-intersections.
* (This is a bad thing; if the user's input data has no intersections,
* we don't want to generate any false intersections ourselves.)
*
* Our eventual goal is to connect vEvent to the leftmost unprocessed
* vertex of the combined region (the union of regUp and regLo).
* But because of unseen vertices with all right-going edges, and also
* new vertices which may be created by edge intersections, we don''t
* know where that leftmost unprocessed vertex is. In the meantime, we
* connect vEvent to the closest vertex of either chain, and mark the region
* as "fixUpperEdge". This flag says to delete and reconnect this edge
* to the next processed vertex on the boundary of the combined region.
* Quite possibly the vertex we connected to will turn out to be the
* closest one, in which case we won''t need to make any changes.
*/
{
GLUhalfEdge *eNew;
GLUhalfEdge *eTopLeft = eBottomLeft->Onext;
ActiveRegion *regLo = RegionBelow(regUp);
GLUhalfEdge *eUp = regUp->eUp;
GLUhalfEdge *eLo = regLo->eUp;
int degenerate = FALSE;
if( eUp->Dst != eLo->Dst ) {
(void) CheckForIntersect( tess, regUp );
}
/* Possible new degeneracies: upper or lower edge of regUp may pass
* through vEvent, or may coincide with new intersection vertex
*/
if( VertEq( eUp->Org, tess->event )) {
if ( !__gl_meshSplice( eTopLeft->Oprev, eUp ) ) longjmp(tess->env,1);
regUp = TopLeftRegion( regUp );
if (regUp == NULL) longjmp(tess->env,1);
eTopLeft = RegionBelow( regUp )->eUp;
FinishLeftRegions( tess, RegionBelow(regUp), regLo );
degenerate = TRUE;
}
if( VertEq( eLo->Org, tess->event )) {
if ( !__gl_meshSplice( eBottomLeft, eLo->Oprev ) ) longjmp(tess->env,1);
eBottomLeft = FinishLeftRegions( tess, regLo, NULL );
degenerate = TRUE;
}
if( degenerate ) {
AddRightEdges( tess, regUp, eBottomLeft->Onext, eTopLeft, eTopLeft, TRUE );
return;
}
/* Non-degenerate situation -- need to add a temporary, fixable edge.
* Connect to the closer of eLo->Org, eUp->Org.
*/
if( VertLeq( eLo->Org, eUp->Org )) {
eNew = eLo->Oprev;
} else {
eNew = eUp;
}
eNew = __gl_meshConnect( eBottomLeft->Lprev, eNew );
if (eNew == NULL) longjmp(tess->env,1);
/* Prevent cleanup, otherwise eNew might disappear before we've even
* had a chance to mark it as a temporary edge.
*/
AddRightEdges( tess, regUp, eNew, eNew->Onext, eNew->Onext, FALSE );
eNew->Sym->activeRegion->fixUpperEdge = TRUE;
WalkDirtyRegions( tess, regUp );
}
/* Because vertices at exactly the same location are merged together
* before we process the sweep event, some degenerate cases can't occur.
* However if someone eventually makes the modifications required to
* merge features which are close together, the cases below marked
* TOLERANCE_NONZERO will be useful. They were debugged before the
* code to merge identical vertices in the main loop was added.
*/
#define TOLERANCE_NONZERO FALSE
static void ConnectLeftDegenerate( GLUtesselator *tess,
ActiveRegion *regUp, GLUvertex *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.
*/
{
GLUhalfEdge *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 (__gl_meshSplitEdge( e->Sym ) == NULL) longjmp(tess->env,1);
if( regUp->fixUpperEdge ) {
/* This edge was fixable -- delete unused portion of original edge */
if ( !__gl_meshDelete( e->Onext ) ) longjmp(tess->env,1);
regUp->fixUpperEdge = FALSE;
}
if ( !__gl_meshSplice( 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 ( !__gl_meshDelete( eTopRight ) ) longjmp(tess->env,1);
eTopRight = eTopLeft->Oprev;
}
if ( !__gl_meshSplice( 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 );
}
static void ConnectLeftVertex( GLUtesselator *tess, GLUvertex *vEvent )
/*
* Purpose: connect a "left" vertex (one where both edges go right)
* to the processed portion of the mesh. Let R be the active region
* containing vEvent, and let U and L be the upper and lower edge
* chains of R. There are two possibilities:
*
* - the normal case: split R into two regions, by connecting vEvent to
* the rightmost vertex of U or L lying to the left of the sweep line
*
* - the degenerate case: if vEvent is close enough to U or L, we
* merge vEvent into that edge chain. The subcases are:
* - merging with the rightmost vertex of U or L
* - merging with the active edge of U or L
* - merging with an already-processed portion of U or L
*/
{
ActiveRegion *regUp, *regLo, *reg;
GLUhalfEdge *eUp, *eLo, *eNew;
ActiveRegion tmp;
/* assert( vEvent->anEdge->Onext->Onext == vEvent->anEdge ); */
/* Get a pointer to the active region containing vEvent */
tmp.eUp = vEvent->anEdge->Sym;
/* __GL_DICTLISTKEY */ /* __gl_dictListSearch */
regUp = (ActiveRegion *)dictKey( dictSearch( tess->dict, &tmp ));
regLo = RegionBelow( regUp );
eUp = regUp->eUp;
eLo = regLo->eUp;
/* Try merging with U or L first */
if( EdgeSign( eUp->Dst, vEvent, eUp->Org ) == 0 ) {
ConnectLeftDegenerate( tess, regUp, vEvent );
return;
}
/* Connect vEvent to rightmost processed vertex of either chain.
* e->Dst is the vertex that we will connect to vEvent.
*/
reg = VertLeq( eLo->Dst, eUp->Dst ) ? regUp : regLo;
if( regUp->inside || reg->fixUpperEdge) {
if( reg == regUp ) {
eNew = __gl_meshConnect( vEvent->anEdge->Sym, eUp->Lnext );
if (eNew == NULL) longjmp(tess->env,1);
} else {
GLUhalfEdge *tempHalfEdge= __gl_meshConnect( eLo->Dnext, vEvent->anEdge);
if (tempHalfEdge == NULL) longjmp(tess->env,1);
eNew = tempHalfEdge->Sym;
}
if( reg->fixUpperEdge ) {
if ( !FixUpperEdge( reg, eNew ) ) longjmp(tess->env,1);
} else {
ComputeWinding( tess, AddRegionBelow( tess, regUp, eNew ));
}
SweepEvent( tess, vEvent );
} else {
/* The new vertex is in a region which does not belong to the polygon.
* We don''t need to connect this vertex to the rest of the mesh.
*/
AddRightEdges( tess, regUp, vEvent->anEdge, vEvent->anEdge, NULL, TRUE );
}
}
static void SweepEvent( GLUtesselator *tess, GLUvertex *vEvent )
/*
* Does everything necessary when the sweep line crosses a vertex.
* Updates the mesh and the edge dictionary.
*/
{
ActiveRegion *regUp, *reg;
GLUhalfEdge *e, *eTopLeft, *eBottomLeft;
tess->event = vEvent; /* for access in EdgeLeq() */
DebugEvent( tess );
/* Check if this vertex is the right endpoint of an edge that is
* already in the dictionary. In this case we don't need to waste
* time searching for the location to insert new edges.
*/
e = vEvent->anEdge;
while( e->activeRegion == NULL ) {
e = e->Onext;
if( e == vEvent->anEdge ) {
/* All edges go right -- not incident to any processed edges */
ConnectLeftVertex( tess, vEvent );
return;
}
}
/* Processing consists of two phases: first we "finish" all the
* active regions where both the upper and lower edges terminate
* at vEvent (ie. vEvent is closing off these regions).
* We mark these faces "inside" or "outside" the polygon according
* to their winding number, and delete the edges from the dictionary.
* This takes care of all the left-going edges from vEvent.
*/
regUp = TopLeftRegion( e->activeRegion );
if (regUp == NULL) longjmp(tess->env,1);
reg = RegionBelow( regUp );
eTopLeft = reg->eUp;
eBottomLeft = FinishLeftRegions( tess, reg, NULL );
/* Next we process all the right-going edges from vEvent. This
* involves adding the edges to the dictionary, and creating the
* associated "active regions" which record information about the
* regions between adjacent dictionary edges.
*/
if( eBottomLeft->Onext == eTopLeft ) {
/* No right-going edges -- add a temporary "fixable" edge */
ConnectRightVertex( tess, regUp, eBottomLeft );
} else {
AddRightEdges( tess, regUp, eBottomLeft->Onext, eTopLeft, eTopLeft, TRUE );
}
}
/* Make the sentinel coordinates big enough that they will never be
* merged with real input features. (Even with the largest possible
* input contour and the maximum tolerance of 1.0, no merging will be
* done with coordinates larger than 3 * GLU_TESS_MAX_COORD).
*/
#define SENTINEL_COORD (4 * GLU_TESS_MAX_COORD)
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 void InitEdgeDict( GLUtesselator *tess )
/*
* We maintain an ordering of edge intersections with the sweep line.
* This order is maintained in a dynamic dictionary.
*/
{
/* __gl_dictListNewDict */
tess->dict = dictNewDict( tess, (int (*)(void *, DictKey, DictKey)) EdgeLeq );
if (tess->dict == NULL) longjmp(tess->env,1);
AddSentinel( tess, -SENTINEL_COORD );
AddSentinel( tess, SENTINEL_COORD );
}
static void DoneEdgeDict( GLUtesselator *tess )
{
ActiveRegion *reg;
#ifndef NDEBUG
int fixedEdges = 0;
#endif
/* __GL_DICTLISTKEY */ /* __GL_DICTLISTMIN */
while( (reg = (ActiveRegion *)dictKey( dictMin( tess->dict ))) != NULL ) {
/*
* At the end of all processing, the dictionary should contain
* only the two sentinel edges, plus at most one "fixable" edge
* created by ConnectRightVertex().
*/
if( ! reg->sentinel ) {
assert( reg->fixUpperEdge );
assert( ++fixedEdges == 1 );
}
assert( reg->windingNumber == 0 );
DeleteRegion( tess, reg );
/* __gl_meshDelete( reg->eUp );*/
}
dictDeleteDict( tess->dict ); /* __gl_dictListDeleteDict */
}
static void RemoveDegenerateEdges( GLUtesselator *tess )
/*
* Remove zero-length edges, and contours with fewer than 3 vertices.
*/
{
GLUhalfEdge *e, *eNext, *eLnext;
GLUhalfEdge *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 ( !__gl_meshDelete( 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 ( !__gl_meshDelete( eLnext ) ) longjmp(tess->env,1);
}
if( e == eNext || e == eNext->Sym ) { eNext = eNext->next; }
if ( !__gl_meshDelete( e ) ) longjmp(tess->env,1);
}
}
}
static int InitPriorityQ( GLUtesselator *tess )
/*
* Insert all vertices into the priority queue which determines the
* order in which vertices cross the sweep line.
*/
{
PriorityQ *pq;
GLUvertex *v, *vHead;
/* __gl_pqSortNewPriorityQ */
pq = tess->pq = pqNewPriorityQ( (int (*)(PQkey, PQkey)) __gl_vertLeq );
if (pq == NULL) return 0;
vHead = &tess->mesh->vHead;
for( v = vHead->next; v != vHead; v = v->next ) {
v->pqHandle = pqInsert( pq, v ); /* __gl_pqSortInsert */
if (v->pqHandle == LONG_MAX) break;
}
if (v != vHead || !pqInit( pq ) ) { /* __gl_pqSortInit */
pqDeletePriorityQ(tess->pq); /* __gl_pqSortDeletePriorityQ */
tess->pq = NULL;
return 0;
}
return 1;
}
static void DonePriorityQ( GLUtesselator *tess )
{
pqDeletePriorityQ( tess->pq ); /* __gl_pqSortDeletePriorityQ */
}
static int RemoveDegenerateFaces( GLUmesh *mesh )
/*
* Delete any degenerate faces with only two edges. WalkDirtyRegions()
* will catch almost all of these, but it won't catch degenerate faces
* produced by splice operations on already-processed edges.
* The two places this can happen are in FinishLeftRegions(), when
* we splice in a "temporary" edge produced by ConnectRightVertex(),
* and in CheckForLeftSplice(), where we splice already-processed
* edges to ensure that our dictionary invariants are not violated
* by numerical errors.
*
* In both these cases it is *very* dangerous to delete the offending
* edge at the time, since one of the routines further up the stack
* will sometimes be keeping a pointer to that edge.
*/
{
GLUface *f, *fNext;
GLUhalfEdge *e;
/*LINTED*/
for( f = mesh->fHead.next; f != &mesh->fHead; f = fNext ) {
fNext = f->next;
e = f->anEdge;
assert( e->Lnext != e );
if( e->Lnext->Lnext == e ) {
/* A face with only two edges */
AddWinding( e->Onext, e );
if ( !__gl_meshDelete( e ) ) return 0;
}
}
return 1;
}
int __gl_computeInterior( GLUtesselator *tess )
/*
* __gl_computeInterior( 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.
*/
{
GLUvertex *v, *vNext;
tess->fatalError = FALSE;
/* 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 );
/* __gl_pqSortExtractMin */
while( (v = (GLUvertex *)pqExtractMin( tess->pq )) != NULL ) {
for( ;; ) {
vNext = (GLUvertex *)pqMinimum( tess->pq ); /* __gl_pqSortMinimum */
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 (GLU_TESS_BOUNDARY_ONLY).
*/
vNext = (GLUvertex *)pqExtractMin( tess->pq ); /* __gl_pqSortExtractMin*/
SpliceMergeVertices( tess, v->anEdge, vNext->anEdge );
}
SweepEvent( tess, v );
}
/* Set tess->event for debugging purposes */
/* __GL_DICTLISTKEY */ /* __GL_DICTLISTMIN */
tess->event = ((ActiveRegion *) dictKey( dictMin( tess->dict )))->eUp->Org;
DebugEvent( tess );
DoneEdgeDict( tess );
DonePriorityQ( tess );
if ( !RemoveDegenerateFaces( tess->mesh ) ) return 0;
__gl_meshCheckMesh( tess->mesh );
return 1;
}