bool Sweep::Legalize(SweepContext& tcx, Triangle& t) { // To legalize a triangle we start by finding if any of the three edges // violate the Delaunay condition for (int i = 0; i < 3; i++) { if (t.delaunay_edge[i]) continue; Triangle* ot = t.GetNeighbor(i); if (ot) { Point* p = t.GetPoint(i); Point* op = ot->OppositePoint(t, *p); int oi = ot->Index(op); // If this is a Constrained Edge or a Delaunay Edge(only during recursive legalization) // then we should not try to legalize if (ot->constrained_edge[oi] || ot->delaunay_edge[oi]) { t.constrained_edge[i] = ot->constrained_edge[oi]; continue; } bool inside = Incircle(*p, *t.PointCCW(*p), *t.PointCW(*p), *op); if (inside) { // Lets mark this shared edge as Delaunay t.delaunay_edge[i] = true; ot->delaunay_edge[oi] = true; // Lets rotate shared edge one vertex CW to legalize it RotateTrianglePair(t, *p, *ot, *op); // We now got one valid Delaunay Edge shared by two triangles // This gives us 4 new edges to check for Delaunay // Make sure that triangle to node mapping is done only one time for a specific triangle bool not_legalized = !Legalize(tcx, t); if (not_legalized) { tcx.MapTriangleToNodes(t); } not_legalized = !Legalize(tcx, *ot); if (not_legalized) tcx.MapTriangleToNodes(*ot); // Reset the Delaunay edges, since they only are valid Delaunay edges // until we add a new triangle or point. // XXX: need to think about this. Can these edges be tried after we // return to previous recursive level? t.delaunay_edge[i] = false; ot->delaunay_edge[oi] = false; // If triangle have been legalized no need to check the other edges since // the recursive legalization will handles those so we can end here. return true; } } } return false; }
void Sweep::FlipScanEdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle& flip_triangle, Triangle& t, Point& p) { Triangle& ot = t.NeighborAcross(p); Point& op = *ot.OppositePoint(t, p); if (&t.NeighborAcross(p) == NULL) { // If we want to integrate the fillEdgeEvent do it here // With current implementation we should never get here //throw new RuntimeException( "[BUG:FIXME] FLIP failed due to missing triangle"); assert(0); } if (InScanArea(eq, *flip_triangle.PointCCW(eq), *flip_triangle.PointCW(eq), op)) { // flip with new edge op->eq FlipEdgeEvent(tcx, eq, op, &ot, op); // TODO: Actually I just figured out that it should be possible to // improve this by getting the next ot and op before the the above // flip and continue the flipScanEdgeEvent here // set new ot and op here and loop back to inScanArea test // also need to set a new flip_triangle first // Turns out at first glance that this is somewhat complicated // so it will have to wait. } else{ Point& newP = NextFlipPoint(ep, eq, ot, op); FlipScanEdgeEvent(tcx, ep, eq, flip_triangle, ot, newP); } }
void SweepContext::MapTriangleToNodes(Triangle& t) { for (int i = 0; i < 3; i++) { if (!t.GetNeighbor(i)) { Node* n = front_->LocatePoint(t.PointCW(*t.GetPoint(i))); if (n) n->triangle = &t; } } }