The zoom plugin allows for modifying the planet's projection's scale with the mouse wheel.
planetaryjs.plugins.zoom([config])
Valid keys for config are:
initialScale: the value to initialize the d3.behavior.zoom object's scale to; defaults to the scale of the planet's projection at the time the planet is initializedscaleExtent: the value to use for the d3.behavior.zoom object's scaleExtent property, which defines how far in and out the planet can be zoomed; defaults to [50, 2000]onZoomStart, onZoomEnd, onZoom, afterZoom: hooks to the d3.behavior.zoom object's zoomstart, zoomend, and zoom events; each defaults to a no-op. onZoom fires at the start of the zoom event, afterZoom at the end. The planet instance is available as this inside the each of the functions.planetaryjs.plugins.zoom({
scaleExtent: [200, 1000],
onZoom: function() {
console.log("The planet was zoomed!", this, d3.event);
}
});