/// <summary>
/// Checks an array of positions that purportedly correspond to a circular arc, to see
/// whether the data is directed clockwise or not. No checks are made to confirm that
/// the data really does correspond to a circular arc.
/// </summary>
/// <param name="pts">The positions defining an arc</param>
/// <param name="center">The position of the centre of the circle that the arc lies on.</param>
/// <returns>True if the data is ordered clockwise.</returns>
public static bool IsClockwise(IPointGeometry[] pts, IPointGeometry center)
{
// To determine the direction, we must locate two successive
// vertices that lie in the same quadrant (with respect to the
// circle center).
QuadVertex start = new QuadVertex(center, pts[0]);
QuadVertex end = null;
for (int i = 1; i < pts.Length; i++, start = end)
{
// Pick up the position at the end of the line segment.
end = new QuadVertex(center, pts[i]);
// If both ends of the segment are in the same quadrant,
// see which one comes first. The result tells us whether
// the curve is clockwise or not.
if (start.Quadrant == end.Quadrant)
{
return(start.GetTanAngle() < end.GetTanAngle());
}
}
// Something has gone wrong if we got here!
Debug.Assert(1 == 2);
return(true);
}
/// <summary>
/// Checks an array of positions that purportedly correspond to a circular arc, to see
/// whether the data is directed clockwise or not. No checks are made to confirm that
/// the data really does correspond to a circular curve.
/// </summary>
/// <param name="pts">Positions on circular arc</param>
/// <param name="center">The position of the centre of the circle that the curve lies on</param>
/// <returns>True if the data is ordered clockwise.</returns>
public static bool IsClockwise(IPosition[] pts, IPosition center)
{
if (pts.Length<2)
return false;
// To determine the direction, we must locate two successive
// vertices that lie in the same quadrant (with respect to the
// circle centre).
QuadVertex start = new QuadVertex(center, pts[0]);
QuadVertex end;
for (int i=1; i<pts.Length; i++, start=end)
{
// Pick up the position at the end of the line segment
end = new QuadVertex(center, pts[i]);
// If both ends of the segment are in the same quadrant,
// see which one comes first. The result tells us whether
// the curve is clockwise or not.
if (start.Quadrant == end.Quadrant)
return (start.GetTanAngle() < end.GetTanAngle() ? true : false);
}
// Something has gone wrong if we got here!
Debug.Assert(1==2);
return true;
}
/// <summary>
/// Gets the most easterly position for this arc.
/// </summary>
/// <returns>The most easterly position</returns>
internal override IPosition GetEastPoint()
{
// If the arc is a complete circle, just work it out the easy way.
if (IsCircle)
{
return(m_Circle.GetEastPoint());
}
// Determine where the east point is. It could be either the
// BC, the EC, or the most easterly point of the circle.
IPosition start = First;
IPosition end = Second;
char choice = (start.X > end.X ? 'S' : choice = 'E');
// But hold on. If the arc passes from the northeast to southeast
// quadrant, we want the east point of the circle.
IPosition c = m_Circle.Center;
QuadVertex vs = new QuadVertex(c, start);
QuadVertex ve = new QuadVertex(c, end);
Quadrant qs = vs.Quadrant;
Quadrant qe = ve.Quadrant;
// If the BC & EC are in the same quadrant, the only way the
// circle point can apply is if it goes all the way round.
if (!(qs == qe && vs.GetTanAngle() < ve.GetTanAngle()))
{
// Determine whether the circle point applies.
switch (qs)
{
case Quadrant.NE:
{
choice = 'C';
break;
}
case Quadrant.SE:
break;
case Quadrant.SW:
{
if (qe == Quadrant.SE)
{
choice = 'C';
}
break;
}
case Quadrant.NW:
{
if (qe != Quadrant.NE)
{
choice = 'C';
}
break;
}
}
}
if (choice == 'S')
{
return(start);
}
else if (choice == 'E')
{
return(end);
}
Debug.Assert(choice == 'C');
return(m_Circle.GetEastPoint());
}
public static IWindow GetExtent(ICircularArcGeometry g)
{
// If the curve is a complete circle, just define it the easy way.
if (g.BC.IsCoincident(g.EC))
return CircleGeometry.GetExtent(g.Circle);
IPosition bcp = g.BC;
IPosition ecp = g.EC;
IPosition centre = g.Circle.Center;
// Initialize the window with the start location.
Window win = new Window(bcp);
// Expand using the end location
win.Union(ecp);
// If the curve is completely within one quadrant, we're done.
QuadVertex bc = new QuadVertex(centre, bcp);
QuadVertex ec = new QuadVertex(centre, ecp);
Quadrant qbc = bc.Quadrant;
Quadrant qec = ec.Quadrant;
if (qbc == qec)
{
if (g.IsClockwise)
{
if (bc.GetTanAngle() < ec.GetTanAngle())
return win;
}
else
{
if (ec.GetTanAngle() < bc.GetTanAngle())
return win;
}
}
// Get the window of the circle
IWindow circle = CircleGeometry.GetExtent(g.Circle);
// If the curve is anticlockwise, switch the quadrants for BC & EC
if (!g.IsClockwise)
{
Quadrant temp = qbc;
qbc = qec;
qec = temp;
}
// Expand the window, depending on which quadrants the start &
// end points fall in. The lack of breaks in the inner switches
// is intentional (e.g. if start & end both fall in Quadrant.NorthEast,
// the window we want is the complete circle, having checked above
// for the case where the arc is JUST in Quadrant.NorthEast).
// Define do-nothing values for the Union's below
double wx = win.Min.X;
double wy = win.Min.Y;
if (qbc==Quadrant.NE)
{
switch (qec)
{
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
break;
}
}
else if (qbc==Quadrant.SE)
{
switch (qec)
{
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
break;
}
}
else if (qbc==Quadrant.SW)
{
switch (qec)
{
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
break;
}
}
else if (qbc==Quadrant.NW)
{
switch (qec)
{
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
break;
}
}
return win;
}
public static IWindow GetExtent(ICircularArcGeometry g)
{
// If the curve is a complete circle, just define it the easy way.
if (g.BC.IsCoincident(g.EC))
{
return(CircleGeometry.GetExtent(g.Circle));
}
IPosition bcp = g.BC;
IPosition ecp = g.EC;
IPosition centre = g.Circle.Center;
// Initialize the window with the start location.
Window win = new Window(bcp);
// Expand using the end location
win.Union(ecp);
// If the curve is completely within one quadrant, we're done.
QuadVertex bc = new QuadVertex(centre, bcp);
QuadVertex ec = new QuadVertex(centre, ecp);
Quadrant qbc = bc.Quadrant;
Quadrant qec = ec.Quadrant;
if (qbc == qec)
{
if (g.IsClockwise)
{
if (bc.GetTanAngle() < ec.GetTanAngle())
{
return(win);
}
}
else
{
if (ec.GetTanAngle() < bc.GetTanAngle())
{
return(win);
}
}
}
// Get the window of the circle
IWindow circle = CircleGeometry.GetExtent(g.Circle);
// If the curve is anticlockwise, switch the quadrants for BC & EC
if (!g.IsClockwise)
{
Quadrant temp = qbc;
qbc = qec;
qec = temp;
}
// Expand the window, depending on which quadrants the start &
// end points fall in. The lack of breaks in the inner switches
// is intentional (e.g. if start & end both fall in Quadrant.NorthEast,
// the window we want is the complete circle, having checked above
// for the case where the arc is JUST in Quadrant.NorthEast).
// Define do-nothing values for the Union's below
double wx = win.Min.X;
double wy = win.Min.Y;
if (qbc == Quadrant.NE)
{
switch (qec)
{
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
break;
}
}
else if (qbc == Quadrant.SE)
{
switch (qec)
{
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
break;
}
}
else if (qbc == Quadrant.SW)
{
switch (qec)
{
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
goto case Quadrant.NW;
case Quadrant.NW:
win.Union(circle.Min.X, wy);
break;
}
}
else if (qbc == Quadrant.NW)
{
switch (qec)
{
case Quadrant.NW:
win.Union(circle.Min.X, wy);
goto case Quadrant.SW;
case Quadrant.SW:
win.Union(wx, circle.Min.Y);
goto case Quadrant.SE;
case Quadrant.SE:
win.Union(circle.Max.X, wy);
goto case Quadrant.NE;
case Quadrant.NE:
win.Union(wx, circle.Max.Y);
break;
}
}
return(win);
}
/// <summary>
/// Gets the most easterly position for this arc.
/// </summary>
/// <returns>The most easterly position</returns>
internal override IPosition GetEastPoint()
{
// If the arc is a complete circle, just work it out the easy way.
if (IsCircle)
return m_Circle.GetEastPoint();
// Determine where the east point is. It could be either the
// BC, the EC, or the most easterly point of the circle.
IPosition start = First;
IPosition end = Second;
char choice = (start.X > end.X ? 'S' : choice = 'E');
// But hold on. If the arc passes from the northeast to southeast
// quadrant, we want the east point of the circle.
IPosition c = m_Circle.Center;
QuadVertex vs = new QuadVertex(c, start);
QuadVertex ve = new QuadVertex(c, end);
Quadrant qs = vs.Quadrant;
Quadrant qe = ve.Quadrant;
// If the BC & EC are in the same quadrant, the only way the
// circle point can apply is if it goes all the way round.
if (!(qs==qe && vs.GetTanAngle()<ve.GetTanAngle()))
{
// Determine whether the circle point applies.
switch (qs)
{
case Quadrant.NE:
{
choice='C';
break;
}
case Quadrant.SE:
break;
case Quadrant.SW:
{
if (qe==Quadrant.SE)
choice = 'C';
break;
}
case Quadrant.NW:
{
if (qe!=Quadrant.NE)
choice = 'C';
break;
}
}
}
if (choice=='S')
return start;
else if (choice=='E')
return end;
Debug.Assert(choice=='C');
return m_Circle.GetEastPoint();
}
