This modifier produces trajectory lines from the time-dependent particle positions. It can be used to visualize the motion paths of particles.
The modifier can either produce trajectory lines for all or just the subset of currently selected particles. Keep in mind that generating and visualizing trajectory lines for simulations with a large number of particles and a large number of timesteps can be prohibitively expensive. Thus, it typically is a good idea to limit the generation of trajectory lines to just a small group of particles of interest.
In systems with periodic boundary conditions, the trajectories written by the MD simulation code for particles which crossed a cell boundary are non-continuous. The Unwrap Trajectories option employs the minimum image convention to make the generated trajectory lines continuous again.
Thebutton starts the line generation process. OVITO will read in all simulation frames one after another and sample the particle positions to produce the trajectory lines. The generated lines will be saved by the modifier, and they will not be updated unless you press the button again.
The following animation shows a system of Lennard-Jones particles flowing around two obstacles. The paths of red marker particles have been visualized as trajectory lines, which were generated by this modifier. The Show up to current time only option has been used to restrict the display of trajectory lines such that they end in the current particle positions.