// Draw the quadtree areas.
public void DrawAreas(Graphics gr, Pen pen)
{
// Draw this quadtree node's area.
gr.DrawRectangle(pen, Area.Left, Area.Top, Area.Width, Area.Height);
// Draw the child nodes.
if (NWchild != null)
{
NWchild.DrawAreas(gr, pen);
NEchild.DrawAreas(gr, pen);
SEchild.DrawAreas(gr, pen);
SWchild.DrawAreas(gr, pen);
}
}
// Draw the points in this quadtree node.
public void DrawPoints(Graphics gr, Brush brush, Pen pen, float radius)
{
// See if this node has children.
if (Points == null)
{
// Make the children draw themselves.
NWchild.DrawPoints(gr, brush, pen, radius);
NEchild.DrawPoints(gr, brush, pen, radius);
SEchild.DrawPoints(gr, brush, pen, radius);
SWchild.DrawPoints(gr, brush, pen, radius);
}
else
{
// Draw the points in this node.
foreach (PointF point in Points)
{
gr.FillEllipse(brush, point.X - radius, point.Y - radius,
2 * radius, 2 * radius);
gr.DrawEllipse(pen, point.X - radius, point.Y - radius,
2 * radius, 2 * radius);
}
}
}
// Add a point to this subtree.
public void AddPoint(PointF newPoint)
{
// See if this quadtree node us full.
if ((Points != null) && (Points.Count + 1 > MaxPoints))
{
// Divide this quadtree node.
float wid = (Area.Right - Area.Left) / 2f;
float hgt = (Area.Bottom - Area.Top) / 2f;
NWchild = new QuadtreeNode(new RectangleF(Area.Left, Area.Top, wid, hgt));
NEchild = new QuadtreeNode(new RectangleF(Area.Left + wid, Area.Top, wid, hgt));
SEchild = new QuadtreeNode(new RectangleF(Area.Left + wid, Area.Top + hgt, wid, hgt));
SWchild = new QuadtreeNode(new RectangleF(Area.Left, Area.Top + hgt, wid, hgt));
// Move the points into the appropriate subtrees.
foreach (PointF pt in Points)
{
if (pt.Y < Ymid)
{
if (pt.X < Xmid)
{
NWchild.AddPoint(pt);
}
else
{
NEchild.AddPoint(pt);
}
}
else
{
if (pt.X < Xmid)
{
SWchild.AddPoint(pt);
}
else
{
SEchild.AddPoint(pt);
}
}
}
// Remove this node's Points list.
Points = null;
}
// Add the point to the appropriate subtree.
if (Points != null)
{
Points.Add(newPoint);
}
else if (newPoint.Y < Ymid)
{
if (newPoint.X < Xmid)
{
NWchild.AddPoint(newPoint);
}
else
{
NEchild.AddPoint(newPoint);
}
}
else
{
if (newPoint.X < Xmid)
{
SWchild.AddPoint(newPoint);
}
else
{
SEchild.AddPoint(newPoint);
}
}
}
// Search the children to find the point closest to the target.
private bool FindPointInChildren(PointF target, float radius, out PointF resultPoint)
{
// The best point we have found so far.
resultPoint = new PointF(float.MinValue, float.MinValue);
float bestDist = float.MaxValue;
// See if the northern subtrees intersect the area of interest.
if (target.Y - radius < Ymid)
{
// See if the northwest subtree intersects the area of interest.
if (target.X - radius < Xmid)
{
// The northwest subtree does intersect the area of interest.
PointF testPoint;
if (NWchild.FindPoint(target, radius, out testPoint))
{
float dx = testPoint.X - target.X;
float dy = testPoint.Y - target.Y;
float testDist = (float)Math.Sqrt(dx * dx + dy * dy);
if ((testDist < radius) && (testDist < bestDist))
{
bestDist = testDist;
resultPoint = testPoint;
}
}
}
// See if the northeast subtree intersects the area of interest.
if (target.X + radius > Xmid)
{
// The northeast subtree does intersect the area of interest.
PointF testPoint;
if (NEchild.FindPoint(target, radius, out testPoint))
{
float dx = testPoint.X - target.X;
float dy = testPoint.Y - target.Y;
float testDist = (float)Math.Sqrt(dx * dx + dy * dy);
if ((testDist < radius) && (testDist < bestDist))
{
bestDist = testDist;
resultPoint = testPoint;
}
}
}
} // End if the northern subtrees intersect the area of interest.
// See if the southern subtrees intersect the area of interest.
if (target.Y + radius > Ymid)
{
// See if the southwest subtree intersects the area of interest.
if (target.X - radius < Xmid)
{
// The southwest subtree does intersect the area of interest.
PointF testPoint;
if (SWchild.FindPoint(target, radius, out testPoint))
{
float dx = testPoint.X - target.X;
float dy = testPoint.Y - target.Y;
float testDist = (float)Math.Sqrt(dx * dx + dy * dy);
if ((testDist < radius) && (testDist < bestDist))
{
bestDist = testDist;
resultPoint = testPoint;
}
}
}
// See if the southeast subtree intersects the area of interest.
if (target.X + radius > Xmid)
{
// The southeast subtree does intersect the area of interest.
PointF testPoint;
if (SEchild.FindPoint(target, radius, out testPoint))
{
float dx = testPoint.X - target.X;
float dy = testPoint.Y - target.Y;
float testDist = (float)Math.Sqrt(dx * dx + dy * dy);
if ((testDist < radius) && (testDist < bestDist))
{
bestDist = testDist;
resultPoint = testPoint;
}
}
}
} // End if the southern subtrees intersect the area of interest.
// Return true if we found a point.
return(bestDist < float.MaxValue);
}