This plugin allows you to insert "Scrolling Overlays" into your posts and pages.
A Scrolling Overlay is a view that appears, covering the whole screen, presenting some sort of media. It displays at the conventional time- when it's scrollheight is in the viewport.
To create an overlay, go to the Scrolling Overlays menu page. Then you can generate shortcodes by selecting images, videos, or inserting a Youtube URL. These shortcodes are then placed directly into a post.