/* ********************************************************************************* */
public static void Create_Control_Point(
PointX Prev, PointX CornerPnt, PointX Next, PointX CtrlPnt) {
PointX before = new PointX(Prev), after = new PointX(Next);
before.Subtract(CornerPnt);
before.Normalize();
after.Subtract(CornerPnt);
after.Normalize();
before.Add(after); // this now divides the angle between the two lines
before.Normalize(); // this gives us normalized output
// CtrlPnt.CopyFrom(before);
double x0, y0, sin, cos;
double d =
(after.x * before.y)
- (after.y * before.x); // winding order: d=(x-x1)*(y2-y1)-(y-y1)*(x2-x1)
if (d > 0) {
sin = Sin90; // 90 degrees
cos = Cos90;
} else {
sin = Sin270; // 270 degrees
cos = Cos270;
}
x0 = (before.x * cos) - (before.y * sin); // precalculated all to constants
y0 = (before.y * cos) + (before.x * sin);
CtrlPnt.Assign(x0, y0); // result is one point, 1 unit long, 'tangent' to the corner.
/*
position = sign((Bx - Ax) * (Y - Ay) - (By - Ay) * (X - Ax))// alternative: cross product
*/
}
