Use Proj4js to convert proj4 or WKT projection definition strings into D3 projections.

// Create Proj4js projection function
var proj4Projection = proj4(wkt);  // WGS84 to projection defined in `wkt`

// Use this to create a D3 projection
var project = function(lambda, phi) {
	return proj4Projection
		.forward([lambda, phi].map(radiansToDegrees));
};

project.invert = function(x, y) {
	return proj4Projection
		.inverse([x, y]).map(degreesToRadians);
};

var projection = d3.geoProjection(project);

Geographic data from Eurostat's GISCO program. The example projections came from Spatial Reference.

forked from <a href='http://bl.ocks.org/armollica/'>armollica</a>'s block: <a href='http://bl.ocks.org/armollica/e6371dcceed6d89312cf6a78be1a0b49'>Proj4/WKT + D3</a>

There are three ways to transition the shapes from one projection to the other:

-- Mike Bostock's and Jason Davies' <a href='https://bl.ocks.org/mbostock/3711652'>projection transitions</a> is probably the correct way to do it

-- Noah Veltman's <a href='http://bl.ocks.org/Fil/9e901b99a6835d489b70a36177e7714b'>flubber</a> interpolates shapes beautifully, but not lines (graticules) yet

-- Peter Beshai's <a href='http://bl.ocks.org/Fil/fbbccd40266014ebe0364da8975a7992'>d3-interpolate-path</a> works well with those graticules since version 2