This is a great question!
mbtile is a type of file that can contain raster or vector fragments. Think of it as an Adobe Illustrator .ai file β it can contain vector or raster data. Raster tiles and vector tiles can be in mbtile format.
With TileMill, your vector data (shapefile, CSV, etc.) was combined with your CartoCSS style and passed to Mapnik to create a bunch of tile images. Then you can save your tiles and send them to the web map through the tile server. Using Mapbox Studio Classic, you convert your data into vector tiles and create a CartoCSS style to style the data, but image tiles are not created until the map is requested through a browser. In the end, the output on the map is the same - a grid of raster fragments.
The interactivity you created in TileMill with bitmap fragments happens through UTFGrid . This is an invisible raster layer that sits beneath the images and adds interactivity to specific places. Interactivity is not actually associated with any individual functions at all - it is in the same place as your functions. This is also possible in Mapbox Studio Classic, since the output on the map will also be a grid of raster fragments. You can learn more about how to do this in Mapbox Studio Classic in a quick-launch style .
So, to answer your question, the transition to Mapbox Studio Classic consisted of using vector plates. They are much smaller than raster images, and they can be styled on the fly, so, for example, you do not need to store two separate sets of images to accommodate retina screens. It also means that you can have multiple styles applied to the same vector data on the fly, which means you donβt need to restore a whole set of images for each style or every small change.
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