// Starting with a valid triangulation, uses the Edge Flip algorithm to
// refine the triangulation into a Constrained Delaunay Triangulation.
void tessMeshRefineDelaunay( TESSmesh *mesh, TESSalloc *alloc )
{
// At this point, we have a valid, but not optimal, triangulation.
// We refine the triangulation using the Edge Flip algorithm
//
// 1) Find all internal edges
// 2) Mark all dual edges
// 3) insert all dual edges into a queue
TESSface *f;
EdgeStack stack;
TESShalfEdge *e;
int maxFaces = 0, maxIter = 0, iter = 0;
stackInit(&stack, alloc);
for( f = mesh->fHead.next; f != &mesh->fHead; f = f->next ) {
if ( f->inside) {
e = f->anEdge;
do {
e->mark = EdgeIsInternal(e); // Mark internal edges
if (e->mark && !e->Sym->mark) stackPush(&stack, e); // Insert into queue
e = e->Lnext;
} while (e != f->anEdge);
maxFaces++;
}
}
// The algorithm should converge on O(n^2), since the predicate is not robust,
// we'll save guard against infinite loop.
maxIter = maxFaces * maxFaces;
// Pop stack until we find a reversed edge
// Flip the reversed edge, and insert any of the four opposite edges
// which are internal and not already in the stack (!marked)
while (!stackEmpty(&stack) && iter < maxIter) {
e = stackPop(&stack);
e->mark = e->Sym->mark = 0;
if (!tesedgeIsLocallyDelaunay(e)) {
TESShalfEdge *edges[4];
int i;
tessMeshFlipEdge(mesh, e);
// for each opposite edge
edges[0] = e->Lnext;
edges[1] = e->Lprev;
edges[2] = e->Sym->Lnext;
edges[3] = e->Sym->Lprev;
for (i = 0; i < 4; i++) {
if (!edges[i]->mark && EdgeIsInternal(edges[i])) {
edges[i]->mark = edges[i]->Sym->mark = 1;
stackPush(&stack, edges[i]);
}
}
}
iter++;
}
stackDelete(&stack);
}
/*
Starting with a valid triangulation, uses the Edge Flip algorithm to
refine the triangulation into a Constrained Delaunay Triangulation.
*/
int tessMeshRefineDelaunay( TESSmesh *mesh, TESSalloc *alloc )
{
/* At this point, we have a valid, but not optimal, triangulation.
We refine the triangulation using the Edge Flip algorithm */
/*
1) Find all internal edges
2) Mark all dual edges
3) insert all dual edges into a queue
*/
TESSface *f;
EdgeStack stack;
TESShalfEdge *e;
TESShalfEdge *edges[4];
stackInit(&stack, alloc);
for( f = mesh->fHead.next; f != &mesh->fHead; f = f->next ) {
if ( f->inside) {
e = f->anEdge;
do {
e->mark = EdgeIsInternal(e); /* Mark internal edges */
if (e->mark && !e->Sym->mark) stackPush(&stack, e); /* Insert into queue */
e = e->Lnext;
} while (e != f->anEdge);
}
}
// Pop stack until we find a reversed edge
// Flip the reversed edge, and insert any of the four opposite edges
// which are internal and not already in the stack (!marked)
while (!stackEmpty(&stack)) {
e = stackPop(&stack);
e->mark = e->Sym->mark = 0;
if (!tesedgeIsLocallyDelaunay(e)) {
int i;
tessMeshFlipEdge(mesh, e);
// for each opposite edge
edges[0] = e->Lnext;
edges[1] = e->Lprev;
edges[2] = e->Sym->Lnext;
edges[3] = e->Sym->Lprev;
for (i=0;i<3;i++) {
if (!edges[i]->mark && EdgeIsInternal(edges[i])) {
edges[i]->mark = edges[i]->Sym->mark = 1;
stackPush(&stack, edges[i]);
}
}
}
}
stackDelete(&stack);
return 1;
}