Smooth trajectory

This modifier smoothes the particle motion by taking into account successive snapshots of a simulation trajectory. Depending on the value of the Smoothing window size parameter, the modifier will either perform a time-based averaging of the particle coordinates over several input frames or a linear interpolation between consecutive frames, see below.

If the particles have orientational information associated with them, then the modifier will smoothen or interpolate the Orientation particle property in the same way as the particle positions.

Averaging mode

If the Smoothing window size parameter is set to a value larger than 1, then the modifier replaces the particle positions in the current frame with time-averaged coordinates computed over a time interval centered around the current frame of the given size, i.e. a sliding window. This mode can be used to reduce fluctuations (e.g. thermal vibrations) in the particle trajectories.

Interpolation mode

If the Smoothing window size parameter is set to 1, the modifier will generate additional intermediate frames in between consecutive snapshots of the input trajectory via linear interpolation. This mode can be used to create more smoothly looking animations from coarse simulation snapshot sequences.

In order to make use of this mode, you should reduce the playback rate of the loaded simulation sequence such that OVITO will render N output animation frames per input simulation snapshot. See this section on how to do this. The Smooth trajectory modifier can then be applied to dynamically compute the particle positions at intermediate sub-frames of the animation.

Periodic boundary conditions

The Use minimum image convention option of the modifier activates the automatic unwrapping of particle coordinates during the interpolation computation, which is needed to handle discontinuities in the trajectories correctly. Normally you should leave this option turned on if the input particle coordinates are given in wrapped form, i.e., if the simulation code has mapped the particles back into the primary simulation cell when using periodic boundary conditions.

If the input particle coordinates are in unwrapped form, i.e., if the input trajectories are already continuous, you can safely turn this option off. The modifier will then take the input particle coordinates as is when computing averages of consecutive snapshots.