Molecular modelers often need to closely inspect the transitions and conformational changes in molecular systems. While forward animations help reveal how a molecule evolves over time, there is often as much insight to be gained by watching it happen in reverse. Whether you’re analyzing how a ligand leaves a binding site or exploring unfolding events frame-by-frame, the ability to play animations backward offers unique benefits.
In SAMSON, a path node stores a trajectory between molecular conformations—whether generated from a simulation, interpolation, or manual deformation. The Play reverse path animation enables you to animate these trajectories from the last frame back to the first. This reverse playback can highlight details that might be missed during forward playback.
When Should You Use Reverse Path Animation?
This animation is especially useful in the following scenarios:
- Backtracking binding events: To study how molecules exit a binding pocket or conformational state.
- Quality-control of trajectory smoothing: Playing a trajectory backward may help identify artifacts or unexpected issues in trajectory transitions.
- Symmetry checking: When a molecule undergoes a cycle of conformational changes, reverse playback can help assess whether the sequence returns to its original shape smoothly.
How to Add Reverse Playback to Your Scene
To use the Play reverse path animation in SAMSON:
- Select the path node that contains the trajectory you want to reverse.
- Open the Animation panel in the Animator.
- Double-click on the Play reverse path animation effect.
- The path will then be automatically played backward between two keyframes. You can move these keyframes to control timing and length.
Customize with Inspector
By default, SAMSON smooths the path if the number of animation frames differs from the number of frames in the original path, but you can turn this off in the Inspector. Additionally, use the Easing curve to control how parameters are interpolated between frames, helping fine-tune the timing of important transitions.
Tip: Synchronize Multiple Paths
If you select multiple paths before adding the animation, they will be played in reverse synchronously. This is especially useful if you’re comparing multiple molecular scenarios side-by-side (e.g., mutant vs. wild-type, or different force field outcomes).
Reverse playback is a simple but insightful tool that can add a new perspective to your visual analysis.
To learn more about this feature and explore additional options, visit the full documentation page:
https://documentation.samson-connect.net/users/latest/animations/play-reverse-path/
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON at https://www.samson-connect.net.