Create a bi-arc curve with an interpolated transition point.

Input parameters:

1. Pa → Bi-arc start point.
2. Ta → Bi-arc start tangent.
3. Pb → Bi-arc end point.
4. Tb → Bi-arc end tangent.
5. In → Interpolation factor between -1 and +1.

Output parameters:

1. Ba → Bi-arc defined by end points and tangents.
2. S1 → First segment of bi-arc. Either null, a line, or an arc.
3. S2 → Second segment of bi-arc. Either null, a line, or an arc.