Function recorded_camera 

pub fn recorded_camera(vantage: Vantage, viewport: Vec2) -> Camera

How a manifest row records vantage (§10.1 of docs/log-vs-snapshot.md): the world point at the centre of viewport, and the zoom.

Centre-and-zoom rather than the translation, which is measured against a window size the reader may no longer have. The pair lives here rather than beside Vantage because the backend does not know the store: it knows where a camera stands, not that anything writes one down.