A molecular model can be carefully prepared and still be difficult to follow in a presentation if the background is distracting, poorly matched to the slide, or changes abruptly between sections. The Set background animation helps address that visual problem: it lets you assign a background at a chosen point in the timeline and, when you use multiple background animations, transition between them.
This is useful when a presentation needs more than one visual setting—for example, a plain backdrop for examining a structure followed by a background image used to introduce a new topic. Instead of manually changing the background while presenting, you can place the changes in the animation timeline and arrange them around the frames where they make sense.
Plan the change around the story
Start by deciding where the audience should notice a change in context. Add the Set background effect by double-clicking it in the Animation panel of the Animator. Its beginning keyframe is placed at the current frame. You can then move the keyframes to adjust when the background is set and how the animation fits into the presentation.
The effect has two keyframes. At the first keyframe, the specified background is set. The second keyframe marks the end of that animation segment. If another Set background animation follows, the presentation interpolates between the backgrounds. In practical terms, this gives you a way to make a background change part of the presentation’s pacing rather than treating it as an unrelated setup step.
For a clear sequence, consider placing a background change near a natural transition in your explanation: when moving from an overview to a close-up, for instance, or when beginning a new section. Keep the visual change purposeful. If the background changes at a moment that does not correspond to a change in the story, it may compete with the molecular model for attention.
Choose how an image fits
You can use an image as a background and choose whether it is fully contained within the presentation area or covers that area. Containing the image keeps the whole image visible, though it may leave unused space around it. Covering fills the area, but the image may be cropped along its largest side. This distinction matters when your background contains text, labels, or other details near its edges: a crop could remove information you intended viewers to see.
Before settling on an image, check how it appears in the presentation area. If the complete image is important, containment is the safer choice. If filling the screen is more important, covering may be appropriate, provided the crop does not hide essential content.
Control the feel of the transition
When multiple backgrounds are present, SAMSON automatically interpolates between them. You can adjust how the parameters are interpolated by changing the easing curve in the Inspector. The easing curve is a useful place to refine the character of the transition: a gradual change can feel less abrupt, while a quicker change can make a section break more apparent. The key is to make the transition support the explanation instead of drawing attention away from it.
As a final check, play through the relevant frames and confirm that the background changes occur when you expect, that any image is framed appropriately, and that the interpolation suits the pace of your presentation. You can move the animation keyframes if the timing needs adjustment.
For the full instructions, see the Set background documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.