This is very similar to what GigaPan uses. GigaPan let’s you embed their player for free but this player give you more control and, of course, no external branding. And krpano offers a neat way to switch rendering options.
It allows you to publish extremely large panoramas where the user only downloads data as they need it.
krpano – is a small, versatile and high-performance viewer for interactive 3D panoramas on the web.