When a molecular trajectory plays, the region you want to inspect can drift away from the center of the view. You may find yourself adjusting the camera just to keep a binding site, ligand, or other selected atoms visible. But moving the camera can also change the perspective you were trying to preserve.
SAMSON’s Look at atoms animation addresses this specific problem: it continuously points the camera at selected atoms while leaving the camera’s position unchanged. In other words, the view can keep tracking a region as it moves, without the camera itself following along through space.
What moves—and what stays fixed?
The camera’s target point moves with the geometric center of the atoms selected when you create the animation. The camera position does not change. This makes the effect useful when you want to keep a moving part of a system in view while preserving the camera location.
That distinction matters. If your goal is to maintain a consistent viewpoint while the structure changes, moving the target can be enough. If you want the camera itself to travel with the atoms, this is not the behavior described for Look at atoms; see the related Follow atoms animation.
Set up the framing before you animate
- Select the atoms whose movement you want the camera to track. The animation uses the atoms selected when it is created.
- Orient the view and camera to establish the camera position and viewpoint you want to keep.
- In the Animator’s Track view, choose the animation’s start frame. In the Animator’s Animation panel, double-click Look at atoms.
- Set the end frame as needed. The camera target moves with the selected atoms’ geometric center between the keyframes; the current camera position is used for both the start and end frames.
Think of the selection as defining what the view should stay centered on, and your initial camera setup as defining where the view is coming from. This can help when preparing a trajectory view: choose the atoms that represent the feature you want to keep visible, then set the camera angle before adding the effect. You can move the animation’s start and end frames later if the timing needs adjustment.
Two settings worth checking
By default, camera animations apply to the active camera. If you need a different behavior, inspect the animation and change Apply to active camera.
Camera positioning can also behave differently depending on whether the grid is on or off. The animation’s Keep camera upwards option controls whether its behavior depends on the grid state. If the resulting view’s orientation is not what you expect, inspect this option rather than changing the atom selection at random.
You can adjust camera position using the animation controllers. The camera target, however, remains at the geometric center of the specified atoms. Keep that in mind when refining the view: adjust the camera position for the perspective, and use the selected atoms to determine what the camera looks toward.
For the full procedure and additional details, see the Look at atoms documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.