In Move3D, the trajectory is described by a sequence of elementary curves (typically straight line segments in the configuration space, arcs of circle for trajectories of car-like robots,...).
The description of a trajectory always starts by the command
p3d_beg_desc P3D_TRAJ traj, that checks checks again if the
description of an environment has been started, if we are not
describing another trajectory at the same time and calls the
function void *p3d_beg_traj(char *name)
with the name
traj. The function p3d_beg_traj allocates an object structure
p3d_trj (cf Annex 
) of name traj,
intializes it, stores it as the current trajectory of the environnemnt
and returns it as an output.
The function int p3d_add_desc_courbe(p3d_courbe *cadd,int
nmaill) adds to the current trajectory the sequence of nmaill
elementary curves of type p3d_courbe (cf Annex
) contained in the list cadd (typically a local
path) . and returns the current number of elementary curves of the
current trajectory.
The function int p3d_end_traj(void) stores the current trajectory in the array of trajectories of the current robot.