/* __gl_meshDelete( eDel ) removes the edge eDel. There are several cases:
* if (eDel->Lface != eDel->Rface), we join two loops into one; the loop
* eDel->Lface is deleted. Otherwise, we are splitting one loop into two;
* the newly created loop will contain eDel->Dst. If the deletion of eDel
* would create isolated vertices, those are deleted as well.
*
* This function could be implemented as two calls to __gl_meshSplice
* plus a few calls to memFree, but this would allocate and delete
* unnecessary vertices and faces.
*/
int __gl_meshDelete(GLUhalfEdge* eDel)
{
GLUhalfEdge* eDelSym=eDel->Sym;
int joiningLoops=FALSE;
/* First step: disconnect the origin vertex eDel->Org. We make all
* changes to get a consistent mesh in this "intermediate" state.
*/
if (eDel->Lface!=eDel->Rface)
{
/* We are joining two loops into one -- remove the left face */
joiningLoops=TRUE;
KillFace(eDel->Lface, eDel->Rface);
}
if (eDel->Onext==eDel)
{
KillVertex(eDel->Org, NULL);
}
else
{
/* Make sure that eDel->Org and eDel->Rface point to valid half-edges */
eDel->Rface->anEdge=eDel->Oprev;
eDel->Org->anEdge=eDel->Onext;
Splice(eDel, eDel->Oprev);
if (!joiningLoops)
{
GLUface* newFace=allocFace();
if (newFace==NULL)
{
return 0;
}
/* We are splitting one loop into two -- create a new loop for eDel. */
MakeFace(newFace, eDel, eDel->Lface);
}
}
/* Claim: the mesh is now in a consistent state, except that eDel->Org
* may have been deleted. Now we disconnect eDel->Dst.
*/
if (eDelSym->Onext==eDelSym)
{
KillVertex(eDelSym->Org, NULL);
KillFace(eDelSym->Lface, NULL);
}
else
{
/* Make sure that eDel->Dst and eDel->Lface point to valid half-edges */
eDel->Lface->anEdge=eDelSym->Oprev;
eDelSym->Org->anEdge=eDelSym->Onext;
Splice(eDelSym, eDelSym->Oprev);
}
/* Any isolated vertices or faces have already been freed. */
KillEdge(eDel);
return 1;
}
/* tessMeshDelete (eDel) removes the edge eDel. There are several cases:
* if (eDel->Lface != eDel->Rface), we join two loops into one; the loop
* eDel->Lface is deleted. Otherwise, we are splitting one loop into two;
* the newly created loop will contain eDel->Dst. If the deletion of eDel
* would create isolated vertices, those are deleted as well.
*
* This function could be implemented as two calls to tessMeshSplice
* plus a few calls to memFree, but this would allocate and delete
* unnecessary vertices and faces.
*/
int tessMeshDelete (TMesh *mesh, THalfEdge *eDel)
{
THalfEdge *eDelSym = eDel->Sym;
int joiningLoops = false;
/* First step: disconnect the origin vertex eDel->Org. We make all
* changes to get a consistent mesh in this "intermediate" state.
*/
if (eDel->Lface != eDel->Rface)
{
/* We are joining two loops into one -- remove the left face */
joiningLoops = true;
KillFace (mesh, eDel->Lface, eDel->Rface) ;
}
if (eDel->Onext == eDel)
{
KillVertex (mesh, eDel->pOrigin, NULL) ;
}
else
{
/* Make sure that eDel->Org and eDel->Rface point to valid half-edges */
eDel->Rface->pHalfEdge = eDel->Oprev;
eDel->pOrigin->pHalfEdge = eDel->Onext;
Splice (eDel, eDel->Oprev) ;
if (! joiningLoops)
{
TFace *newFace= (TFace*)BucketAlloc (mesh->pFaceBucket) ;
if (newFace == NULL) return 0;
/* We are splitting one loop into two -- create a new loop for eDel. */
MakeFace (newFace, eDel, eDel->Lface) ;
}
}
/* Claim: the mesh is now in a consistent state, except that eDel->Org
* may have been deleted. Now we disconnect eDel->Dst.
*/
if (eDelSym->Onext == eDelSym)
{
KillVertex (mesh, eDelSym->pOrigin, NULL) ;
KillFace (mesh, eDelSym->Lface, NULL) ;
}
else
{
/* Make sure that eDel->Dst and eDel->Lface point to valid half-edges */
eDel->Lface->pHalfEdge = eDelSym->Oprev;
eDelSym->pOrigin->pHalfEdge = eDelSym->Onext;
Splice (eDelSym, eDelSym->Oprev) ;
}
/* Any isolated vertices or faces have already been freed. */
KillEdge (mesh, eDel) ;
return 1;
}
/* __gl_meshZapFace(fZap) destroys a face and removes it from the
* global face list. All edges of fZap will have a NULL pointer as their
* left face. Any edges which also have a NULL pointer as their right face
* are deleted entirely (along with any isolated vertices this produces).
* An entire mesh can be deleted by zapping its faces, one at a time,
* in any order. Zapped faces cannot be used in further mesh operations!
*/
void __gl_meshZapFace(GLUface* fZap)
{
GLUhalfEdge* eStart=fZap->anEdge;
GLUhalfEdge* e, *eNext, *eSym;
GLUface* fPrev, *fNext;
/* walk around face, deleting edges whose right face is also NULL */
eNext=eStart->Lnext;
do {
e=eNext;
eNext=e->Lnext;
e->Lface=NULL;
if (e->Rface==NULL)
{
/* delete the edge -- see __gl_MeshDelete above */
if (e->Onext==e)
{
KillVertex(e->Org, NULL);
}
else
{
/* Make sure that e->Org points to a valid half-edge */
e->Org->anEdge=e->Onext;
Splice(e, e->Oprev);
}
eSym=e->Sym;
if (eSym->Onext==eSym)
{
KillVertex(eSym->Org, NULL);
}
else
{
/* Make sure that eSym->Org points to a valid half-edge */
eSym->Org->anEdge=eSym->Onext;
Splice(eSym, eSym->Oprev);
}
KillEdge(e);
}
} while(e!=eStart);
/* delete from circular doubly-linked list */
fPrev=fZap->prev;
fNext=fZap->next;
fNext->prev=fPrev;
fPrev->next=fNext;
memFree(fZap);
}
/* tessMeshZapFace (fZap) destroys a face and removes it from the
* global face list. All edges of fZap will have a NULL pointer as their
* left face. Any edges which also have a NULL pointer as their right face
* are deleted entirely (along with any isolated vertices this produces).
* An entire mesh can be deleted by zapping its faces, one at a time,
* in any order. Zapped faces cannot be used in further mesh operations!
*/
void tessMeshZapFace (TMesh *mesh, TFace *fZap)
{
THalfEdge *eStart = fZap->pHalfEdge;
THalfEdge *e, *eNext, *eSym;
TFace *fPrev, *fNext;
/* walk around face, deleting edges whose right face is also NULL */
eNext = eStart->Lnext;
do {
e = eNext;
eNext = e->Lnext;
e->Lface = NULL;
if (e->Rface == NULL) {
/* delete the edge -- see TESSmeshDelete above */
if (e->Onext == e) {
KillVertex (mesh, e->pOrigin, NULL) ;
} else {
/* Make sure that e->Org points to a valid half-edge */
e->pOrigin->pHalfEdge = e->Onext;
Splice (e, e->Oprev) ;
}
eSym = e->Sym;
if (eSym->Onext == eSym) {
KillVertex (mesh, eSym->pOrigin, NULL) ;
} else {
/* Make sure that eSym->Org points to a valid half-edge */
eSym->pOrigin->pHalfEdge = eSym->Onext;
Splice (eSym, eSym->Oprev) ;
}
KillEdge (mesh, e) ;
}
} while (e != eStart) ;
/* delete from circular doubly-linked list */
fPrev = fZap->pPrev;
fNext = fZap->pNext;
fNext->pPrev = fPrev;
fPrev->pNext = fNext;
BucketFree (mesh->pFaceBucket, fZap) ;
}
