Renders GeoJSON geometries as SVG path strings.

Takes GeoJSON data and a projection to produce SVG paths suitable for rendering maps.

Examples

projection = Visualize.Geo.Projection.new(:mercator)
  |> Visualize.Geo.Projection.scale(100)
  |> Visualize.Geo.Projection.translate(200, 150)

geo_path = Visualize.Geo.Path.new(projection)

# Render a GeoJSON feature
feature = %{
  "type" => "Feature",
  "geometry" => %{
    "type" => "Polygon",
    "coordinates" => [[[-122, 37], [-122, 38], [-121, 38], [-121, 37], [-122, 37]]]
  }
}

path_data = Visualize.Geo.Path.render(geo_path, feature)

Clipping on the sphere

With a projection, lines and polygons are clipped on the sphere before they are projected, as d3-geo clips them (spec/07 §2.2.1, D-127): under a projection with a clip_angle they are cut where they cross the small circle of that radius about the centre — the orthographic's horizon — a line into several subpaths and a polygon closed along the circle, so a globe never closes its land by a chord across the disc; under a projection without one they are cut where they cross ±180° of the rotated frame and a polygon is closed along the seam and the poles, so a rotated map never joins a ring the long way round. Winding is d3's: a polygon's exterior ring runs clockwise on a north-up map, and a ring wound the other way is the rest of the sphere.