/// <summary>
/// Apply a transform to us.
/// </summary>
private void TransformInternal <T>(T transform) where T : ITransform
{
// NOTES:
// Arcs can go to lines, and lines to arcs.
// Rotations may reverse arc directions as well.
// Arc centers can't be transformed directly.
// NOTE: We must calc this before altering the endpoints.
Vector3D mid = Midpoint;
if (Infinity.IsInfinite(mid))
{
mid = Infinity.IsInfinite(P1) ? P2 * Infinity.FiniteScale : P1 * Infinity.FiniteScale;
}
P1 = transform.Apply(P1);
P2 = transform.Apply(P2);
mid = transform.Apply(mid);
// Can we make a circle out of the transformed points?
Circle temp = new Circle();
if (!Infinity.IsInfinite(P1) && !Infinity.IsInfinite(P2) && !Infinity.IsInfinite(mid) &&
temp.From3Points(P1, mid, P2))
{
Type = SegmentType.Arc;
Center = temp.Center;
// Work out the orientation of the arc.
Vector3D t1 = P1 - Center;
Vector3D t2 = mid - Center;
Vector3D t3 = P2 - Center;
double a1 = Euclidean2D.AngleToCounterClock(t2, t1);
double a2 = Euclidean2D.AngleToCounterClock(t3, t1);
Clockwise = a2 > a1;
}
else
{
// The circle construction fails if the points
// are colinear (if the arc has been transformed into a line).
Type = SegmentType.Line;
// XXX - need to do something about this.
// Turn into 2 segments?
//if( isInfinite( mid ) )
// Actually the check should just be whether mid is between p1 and p2.
}
}
public static Segment Arc(Vector3D start, Vector3D mid, Vector3D end)
{
Segment newSeg = new Segment();
newSeg.Type = SegmentType.Arc;
newSeg.P1 = start;
newSeg.P2 = end;
Circle c = new Circle();
c.From3Points(start, mid, end);
newSeg.Center = c.Center;
// Obtain vectors from center point of circle (as if at the origin)
Vector3D startOrigin = start - c.Center;
Vector3D midOrigin = mid - c.Center;
Vector3D endOrigin = end - c.Center;
// Calculate the normal vector and angle to traverse.
// ZZZ - worry about failure of cross product here.
Vector3D normalVector = startOrigin.Cross(endOrigin);
newSeg.Clockwise = normalVector.Z < 0;
double angleToTraverse = startOrigin.AngleTo(endOrigin);
// The normal vector might need to be reversed and the angleToTraverse adjusted.
// This happens depending on the location of the midpoint relative to the start and end points.
double compareAngle = startOrigin.AngleTo(midOrigin) + midOrigin.AngleTo(endOrigin);
bool reverse = !Tolerance.Equal(angleToTraverse, compareAngle);
if (reverse)
{
newSeg.Clockwise = !newSeg.Clockwise;
}
return(newSeg);
}
