Trace a trajectory through a vector field starting at a point.

Input parameters:

1. Fl → Field to measure.
2. Pt → Start of trajectory.
3. An → Maximum allowed angle between adjacent trajectory segments.
4. Ln → Maximum allowed length of trajectory.
5. Sl → Differential solver to use while sampling the trajectory.
   • 0 → Euler
   • 1 → Runge-Kutta 2
   • 2 → Runge-Kutta 3
   • 3 → Runge-Kutta 4

Output parameters:

1. Tj → Trajectory curve.