A molecular trajectory can be difficult to interpret when you only watch it move forward. You may want to revisit the starting conformation, compare the two ends of a path, or create a presentation that shows a structural change in the opposite direction. Rebuilding or duplicating a trajectory just to change its playback direction adds unnecessary work.
In SAMSON, the Play reverse path animation plays a selected path—or several selected paths—in reverse between two animation frames. It provides a direct way to inspect or present an existing trajectory from its endpoint back to its beginning.
Use the path you already have
A path node stores a trajectory in SAMSON. To use it, select the path you want to play, then double-click Play reverse path in the Animation panel of the Animator. The animation plays the whole path in reverse between its two keyframes.
This is useful when the direction of playback affects how a viewer understands a conformational change. Showing the same path backward can make it easier to focus on where a structure ends up, or to compare the final and initial states without changing which path is being shown. It can also help when preparing an animation whose sequence needs to run from a later frame toward an earlier one.
Set the timing with keyframes
The animation’s keyframes determine the interval over which the reverse playback occurs. After adding the animation, move the keyframes as needed to fit the sequence into your animation. You can move them later as well, so the timing does not need to be final when you first add the effect.
When planning a presentation, separate two questions: which part of the animation should show the reverse path? and how much time should that playback occupy? The selected path determines the motion; the keyframes give you control over where it plays in the animation.
What if the frame counts differ?
If the animation and the path contain different numbers of frames, the path is smoothed. This helps accommodate the difference between the two frame counts. If you do not want smoothing, you can switch it off in the Inspector. This setting is worth checking when the animation does not look the way you expect: the difference may be related to the frame-count mismatch and smoothing, rather than to the choice of playback direction.
Playing several paths together
You can select multiple paths before adding the animation. When several paths are selected, they are synchronized during playback. This can be useful when you want multiple paths to run together as part of the same animation. Before building a longer presentation around them, check that you selected the intended paths and that their timing fits the keyframe interval.
Adjust the transitions
The Easing curve controls how parameters are interpolated between frames. If the pacing of the animation feels too abrupt or too gradual, adjust the easing curve in the animation properties. Easing changes the interpolation between frames; it does not change the fact that the selected path is being played in reverse.
A quick setup checklist
- Select the path or paths you want to show.
- Add Play reverse path from the Animator’s Animation panel.
- Position the animation keyframes to set its interval.
- If frame counts differ, review the smoothing setting in the Inspector.
- Adjust the Easing curve if you want to change interpolation between frames.
Reverse playback gives you another way to examine and communicate a stored trajectory, without needing to treat the reverse view as a separate path. For the full procedure and animation details, see the Play reverse path documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON at samson-connect.net.