Keep a moving molecular region in frame without chasing it by hand

When a molecular system moves through a trajectory, the camera can quickly lose the region you are trying to study. Repeatedly adjusting the view interrupts inspection and makes it harder to create a clear animation. In SAMSON, the Follow atoms animation can keep a chosen group in view while its position changes.

The key is to select the atoms that define the region you want to track. After you create the animation, SAMSON moves the camera target with the geometric center of those selected atoms. The camera position moves along with the target, preserving the distance between the camera and the atoms. This lets you watch motion without the tracked group simply drifting out of frame.

Choose what the camera should follow

Before adding the animation, select the atoms whose motion matters for your view. That might be a moving part of a larger structure or another region whose trajectory you want to inspect. The selection at the time the animation is created determines what the camera follows, so take a moment to check that it represents the object of interest—not the entire system if you want to focus on just one part.

Next, orient the camera as you want it to look at the start of the animation. The starting camera position is used for the first frame. This is a useful distinction: Follow atoms handles keeping the selected region centered as it moves, while your initial view determines the starting composition.

Set up the tracking interval

1. Select the atoms to follow.
2. Position and orient the view for the start of the shot.
3. In the Animator’s Track view, choose the start frame.
4. In the Animator’s Animation panel, double-click Follow atoms.
5. Set the end frame to cover the portion of the trajectory you want to show.

The animation can be placed and adjusted in time: you can move its start and end frames. This makes it possible to match the tracking interval to the part of the trajectory you want viewers to see, rather than following the atoms for longer than necessary.

Fine-tune the camera behavior

By default, camera animations apply to the active camera. If you need the animation to apply differently, inspect it and change Apply to active camera. The animation’s target point is based on the active camera’s current target position, which is essentially the center of the current view.

Camera positioning can also behave differently depending on whether the grid is on or off. If that affects the shot, inspect the animation’s Keep camera upwards option. The documentation notes that, when this option is checked, the behavior depends on whether the grid is enabled.

You can adjust the camera position with the animation controllers. Keep in mind that the target remains tied to the geometric center of the selected atoms. In practice, this means you can refine where the camera sits while the tracked group remains the point the camera follows.

A quick way to diagnose an awkward shot

• The wrong region is centered: check which atoms were selected when the animation was created.
• The starting view feels wrong: return to the start frame and orient the camera before creating the animation.
• The tracking runs for too long or too briefly: adjust the animation’s start or end frame.
• The camera’s upward orientation changes unexpectedly: inspect the Keep camera upwards setting and check whether the grid is on or off.

Use Follow atoms when the camera should travel with a moving selection. If instead you want the camera to look at selected atoms without following their movement, see the related Look at atoms animation.

For the complete instructions, see the Follow atoms documentation.

Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.