Molecular modeling often involves exploring how molecules transition from one conformation to another. These trajectories can contain vital insights about the stability and behavior of biological systems, materials, or reactions. But what happens when you want to focus not only on how a system evolves, but also how it effectively returns to a prior state?
This can be particularly useful when analyzing symmetric transitions or when preparing animations for presentations or publications that require directionality control. In many cases, researchers want to reverse a molecular path — either to analyze it or to create smooth looping animations. With SAMSON, this is possible through the Play reverse path animation.
Why Reverse Paths?
Imagine you are simulating a protein folding process. You’ve observed the path from unfolded to folded states using a simulation embedded in a Path node in SAMSON — the data structure used to store trajectories. Now, you want to create an animation for your talk that shows both folding and unfolding. Creating a seamless loop for this purpose is possible by simply playing the animation forward and then backward.
The Play reverse path animation helps solve this pain point: it lets you reverse one or more paths between two keyframes in your animation timeline, without needing to pre-process or duplicate trajectory data.
How It Works
To add this animation:
- Select the path (or multiple paths) you want to animate. You’ll find your paths usually created via simulation or manual manipulation, stored under Path nodes.
- Open the Animation panel in the Animator (accessible from the Animator section).
- Double-click on Play reverse path to apply the effect between two keyframes.
- Adjust keyframe positions on the timeline to control speed and duration.
If the number of frames in your animation doesn’t match the number of frames in your chosen path, SAMSON will automatically smooth the trajectory. This smoothing ensures interpolation between points stays fluid. However, if for scientific reasons you want frame-perfect correspondences (for example, analyzing a specific molecular mechanism), you can disable smoothing in the Inspector.
Fine-Tuning the Animation
In the Inspector, you’ll also find options to control the interpolation using Easing curves. These curves allow you to adjust how the values (like position and rotation) transition throughout the animation, providing more precise control. For instance, you might want a slow start and a fast finish.
There’s also a visual indicator for the animation effect within the timeline, so you can quickly reference and modify it.
Example: Seeing It in Action
Here’s what a reverse path animation looks like when applied to a molecular system:
This feature can be a practical tool not only for scientific storytelling but also for deeper trajectory diagnostics.
To explore this animation in more depth, visit the official SAMSON documentation page.
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON at https://www.samson-connect.net.