Ejemplo n.º 1
0
        private void EdgeEvent(SweepContext tcx, TriPoint ep, TriPoint eq, Triangle triangle, TriPoint point)
        {
            if (IsEdgeSideOfTriangle(triangle, ep, eq))
            {
                return;
            }

            TriPoint p1 = triangle.PointCCW(point);
            Winding  o1 = TriUtil.Orient2d(eq, p1, ep);

            if (o1 == Winding.Collinear)
            {
                if (triangle.Contains(eq, p1))
                {
                    triangle.MarkConstrainedEdge(eq, p1);
                    // We are modifying the constraint maybe it would be better to
                    // not change the given constraint and just keep a variable for the new constraint
                    tcx.EdgeEvent.ConstrainedEdge.Q = p1;
                    triangle = triangle.NeighborAcross(point);
                    EdgeEvent(tcx, ep, p1, triangle, p1);
                }
                else
                {
                    throw new NotSupportedException("EdgeEvent - collinear points not supported");
                }

                return;
            }

            TriPoint p2 = triangle.PointCW(point);
            Winding  o2 = TriUtil.Orient2d(eq, p2, ep);

            if (o2 == Winding.Collinear)
            {
                if (triangle.Contains(eq, p2))
                {
                    triangle.MarkConstrainedEdge(eq, p2);
                    // We are modifying the constraint maybe it would be better to
                    // not change the given constraint and just keep a variable for the new constraint
                    tcx.EdgeEvent.ConstrainedEdge.Q = p2;
                    triangle = triangle.NeighborAcross(point);
                    EdgeEvent(tcx, ep, p2, triangle, p2);
                }
                else
                {
                    throw new NotSupportedException("EdgeEvent - collinear points not supported");
                }

                return;
            }

            if (o1 == o2)
            {
                // Need to decide if we are rotating CW or CCW to get to a triangle
                // that will cross edge
                if (o1 == Winding.CW)
                {
                    triangle = triangle.NeighborCCW(point);
                }
                else
                {
                    triangle = triangle.NeighborCW(point);
                }
                EdgeEvent(tcx, ep, eq, triangle, point);
            }
            else
            {
                // This triangle crosses constraint so lets flippin start!
                FlipEdgeEvent(tcx, ep, eq, triangle, point);
            }
        }
Ejemplo n.º 2
0
        /**
         * Rotates a triangle pair one vertex CW
         *<pre>
         *       n2                    n2
         *  P +-----+             P +-----+
         *    | t  /|               |\  t |
         *    |   / |               | \   |
         *  n1|  /  |n3           n1|  \  |n3
         *    | /   |    after CW   |   \ |
         *    |/ oT |               | oT \|
         *    +-----+ oP            +-----+
         *       n4                    n4
         * </pre>
         */
        private void RotateTrianglePair(Triangle t, TriPoint p, Triangle ot, TriPoint op)
        {
            Triangle n1, n2, n3, n4;

            n1 = t.NeighborCCW(p);
            n2 = t.NeighborCW(p);
            n3 = ot.NeighborCCW(op);
            n4 = ot.NeighborCW(op);

            bool ce1, ce2, ce3, ce4;

            ce1 = t.GetConstrainedEdgeCCW(p);
            ce2 = t.GetConstrainedEdgeCW(p);
            ce3 = ot.GetConstrainedEdgeCCW(op);
            ce4 = ot.GetConstrainedEdgeCW(op);

            bool de1, de2, de3, de4;

            de1 = t.GetDelaunayEdgeCCW(p);
            de2 = t.GetDelaunayEdgeCW(p);
            de3 = ot.GetDelaunayEdgeCCW(op);
            de4 = ot.GetDelaunayEdgeCW(op);

            t.Legalize(p, op);
            ot.Legalize(op, p);

            // Remap delaunay_edge
            ot.SetDelunayEdgeCCW(p, de1);
            t.SetDelunayEdgeCW(p, de2);
            t.SetDelunayEdgeCCW(op, de3);
            ot.SetDelunayEdgeCW(op, de4);

            // Remap constrained_edge
            ot.SetConstrainedEdgeCCW(p, ce1);
            t.SetConstrainedEdgeCW(p, ce2);
            t.SetConstrainedEdgeCCW(op, ce3);
            ot.SetConstrainedEdgeCW(op, ce4);

            // Remap neighbors
            // XXX: might optimize the markNeighbor by keeping track of
            //      what side should be assigned to what neighbor after the
            //      rotation. Now mark neighbor does lots of testing to find
            //      the right side.
            t.ClearNeighbors();
            ot.ClearNeighbors();
            if (n1 != null)
            {
                ot.MarkNeighbor(n1);
            }
            if (n2 != null)
            {
                t.MarkNeighbor(n2);
            }
            if (n3 != null)
            {
                t.MarkNeighbor(n3);
            }
            if (n4 != null)
            {
                ot.MarkNeighbor(n4);
            }
            t.MarkNeighbor(ot);
        }
Ejemplo n.º 3
0
        private void FlipScanEdgeEvent(SweepContext tcx, TriPoint ep, TriPoint eq, Triangle flip_triangle, Triangle t, TriPoint p)
        {
            Triangle ot = t.NeighborAcross(p);
            TriPoint op = ot.OppositePoint(t, p);

            if (TriUtil.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
            {
                TriPoint newP = NextFlipPoint(ep, eq, ot, op);
                FlipScanEdgeEvent(tcx, ep, eq, flip_triangle, ot, newP);
            }
        }
Ejemplo n.º 4
0
        private bool 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.DelaunayEdge[i])
                {
                    continue;
                }

                Triangle ot = t.GetNeighbor(i);

                if (ot != null)
                {
                    TriPoint p  = t.Points[i];
                    TriPoint 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.ConstrainedEdge[oi] || ot.DelaunayEdge[oi])
                    {
                        t.ConstrainedEdge[i] = ot.ConstrainedEdge[oi];
                        continue;
                    }

                    bool inside = Incircle(p, t.PointCCW(p), t.PointCW(p), op);

                    if (inside)
                    {
                        // Lets mark this shared edge as Delaunay
                        t.DelaunayEdge[i]   = true;
                        ot.DelaunayEdge[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.DelaunayEdge[i]   = false;
                        ot.DelaunayEdge[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);
        }