//
// We want our first vector to be downward (-90 degrees std unit circle)
//
private Point GetFirstNeighbor(Point currentPt)
{
Point imaginaryPrevPt = new Point("", currentPt.X, currentPt.Y + 1);
Point prevCurrVector = Point.MakeVector(imaginaryPrevPt, currentPt);
// We want the point that creates the smallest angle w.r.t. to the stdVector
// Information that will change along with the current candidate next point.
double currentAngle = 360; // This will be overwritten
Point currentNextPoint = null;
// Index of the current point so we can get its neighbors.
int currentPtIndex = graph.IndexOf(currentPt);
foreach (UndirectedPlanarGraph.PlanarGraphEdge edge in graph.nodes[currentPtIndex].edges)
{
int neighborIndex = graph.IndexOf(edge.target);
Point neighbor = graph.nodes[neighborIndex].thePoint;
// Create a vector of the current point with it's neighbor
Point currentNeighborVector = Point.MakeVector(currentPt, neighbor);
// Cross product of the two vectors to determine if we have an angle that is < 180 or > 180.
double crossProduct = Point.CrossProduct(prevCurrVector, currentNeighborVector);
double angleMeasure = Point.AngleBetween(prevCurrVector, currentNeighborVector);
// if (GeometryTutorLib.Utilities.GreaterThan(crossProduct, 0)) angleMeasure = angleMeasure;
if (GeometryTutorLib.Utilities.CompareValues(crossProduct, 0))
{
angleMeasure = 180;
}
else if (crossProduct < 0)
{
angleMeasure = 360 - angleMeasure;
}
// If there are have the same angle, choose the one farther away (it is due to two connections)
// So these points are collinear with a segment, but indistinguishable with two arcs.
if (Utilities.CompareValues(angleMeasure, currentAngle))
{
double currentDist = Point.calcDistance(currentPt, currentNextPoint);
double candDist = Point.calcDistance(currentPt, neighbor);
// Take the farthest point.
if (candDist > currentDist)
{
currentAngle = angleMeasure;
currentNextPoint = neighbor;
}
}
else if (angleMeasure < currentAngle)
{
currentAngle = angleMeasure;
currentNextPoint = neighbor;
}
}
return(currentNextPoint);
}
/// <summary>
/// Draws a line.
/// </summary>
/// <param name="pen">The pen.</param>
/// <param name="p1">The first point.</param>
/// <param name="p2">The second point.</param>
public void DrawLine(Pen pen, Point p1, Point p2)
{
double angle = p1.AngleBetween(p2);
float halfWidth = Math.Max(1, pen.Width / 2.0f);
var size = this.ViewportSize;
var quad = new Quad();
quad.SetVertexLocations(
p1.MoveAlongAngle(angle + 90, halfWidth).ToScreenCoordinates(size),
p1.MoveAlongAngle(angle - 90, halfWidth).ToScreenCoordinates(size),
p2.MoveAlongAngle(angle - 90, halfWidth).ToScreenCoordinates(size),
p2.MoveAlongAngle(angle + 90, halfWidth).ToScreenCoordinates(size));
quad.SetVertexUVs(new RectangleF(0, 0, 1, 1));
this.CreateSprite(pen, quad);
}
//
// With respect to the given vector (based on prevPt and currentPt), return the tightest counter-clockwise neighbor.
//
private Point GetTightestCounterClockwiseNeighbor(Point prevPt, Point currentPt)
{
Point prevCurrVector = Point.MakeVector(prevPt, currentPt);
// We want the point that creates the smallest angle w.r.t. to the stdVector
// Information that will change along with the current candidate next point.
double currentAngle = 360; // This will be overwritten
Point currentNextPoint = null;
// Index of the current point so we can get its neighbors.
int prevPtIndex = graph.IndexOf(prevPt);
int currentPtIndex = graph.IndexOf(currentPt);
foreach (UndirectedPlanarGraph.PlanarGraphEdge edge in graph.nodes[currentPtIndex].edges)
{
int neighborIndex = graph.IndexOf(edge.target);
if (prevPtIndex != neighborIndex)
{
Point neighbor = graph.nodes[neighborIndex].thePoint;
// Create a vector of the current point with it's neighbor
Point currentNeighborVector = Point.MakeVector(currentPt, neighbor);
// Cross product of the two vectors to determine if we have an angle that is < 180 or > 180.
double crossProduct = Point.CrossProduct(prevCurrVector, currentNeighborVector);
double angleMeasure = Point.AngleBetween(Point.GetOppositeVector(prevCurrVector), currentNeighborVector);
// if (GeometryTutorLib.Utilities.GreaterThan(crossProduct, 0)) angleMeasure = angleMeasure;
if (GeometryTutorLib.Utilities.CompareValues(crossProduct, 0))
{
// Circles create a legitimate situation where we want to walk back in the same 'collinear' path.
if (Point.OppositeVectors(prevCurrVector, currentNeighborVector))
{
throw new System.Exception("FacetCalculator has collinear points in graph, but a cycle in the edges.");
}
else
{
angleMeasure = 180;
}
}
else if (crossProduct < 0)
{
angleMeasure = 360 - angleMeasure;
}
// If there are have the same angle, choose the one farther away (it is due to two connections)
// So these points are collinear with a segment, but indistinguishable with two arcs.
if (Utilities.CompareValues(angleMeasure, currentAngle))
{
double currentDist = Point.calcDistance(currentPt, currentNextPoint);
double candDist = Point.calcDistance(currentPt, neighbor);
// Take the farthest point.
if (candDist > currentDist)
{
currentAngle = angleMeasure;
currentNextPoint = neighbor;
}
}
if (angleMeasure < currentAngle)
{
currentAngle = angleMeasure;
currentNextPoint = neighbor;
}
}
}
return(currentNextPoint);
}
