d3-geo-polygon

Clipping and geometric operations for spherical polygons.

Installing

If you use NPM, npm install d3-geo-polygon. Otherwise, download the latest release. You can also load directly from unpkg. AMD, CommonJS, and vanilla environments are supported. In vanilla, a d3 global is exported:

<script src="https://unpkg.com/d3-geo@1"></script>
<script src="https://unpkg.com/d3-geo-polygon@1"></script>
<script>

// new projection
var projection = d3.geoDodecahedral();

// polyhedral projections don’t need SVG or canvas clipping anymore
var projection = d3.geoPolyhedralCollignon();

// arbitrary polygon clipping on any projection
var projection = d3.geoEquirectangular()
    .preclip(d3.geoClipPolygon({
      type: "Polygon",
      coordinates: [[[-10, -10], [-10, 10], [10, 10], [10, -10], [-10, -10]]]
    }));

</script>

API Reference

d3.geoClipPolygon(polygon) Source

Given a GeoJSON polygon or multipolygon, returns a clip function suitable for projection.preclip.

clip.polygon()

Given a clipPolygon function, returns the GeoJSON polygon.

Projections

d3-geo-polygon adds polygon clipping to the polyhedral projections from d3-geo-projection. Thus, it supercedes the following symbols:

d3.geoPolyhedral(tree, face) Source

Defines a new polyhedral projection. The tree is a spanning tree of polygon face nodes; each node is assigned a node.transform matrix. The face function returns the appropriate node for a given lambda and phi in radians.

polyhedral.tree() returns the spanning tree of the polyhedron, from which one can infer the faces’ centers, polygons, shared edges etc.

d3.geoPolyhedralButterfly() Source

The gnomonic butterfly projection.

d3.geoPolyhedralCollignon() Source

The Collignon butterfly projection.

d3.geoPolyhedralWaterman() Source

A butterfly projection inspired by Steve Waterman’s design.

New projections are introduced:

d3.geoPolyhedralVoronoi([parents], [polygons], [faceProjection], [faceFind]) Source

Returns a polyhedral projection based on the polygons, arranged in a tree according to the parents list. polygons are a GeoJSON FeatureCollection of geoVoronoi cells, which should indicate the corresponding sites (see d3-geo-voronoi). An optional faceProjection is passed to d3.geoPolyhedral() -- note that the gnomonic projection on the polygons’ sites is the only faceProjection that works in the general case.

The .parents([parents]), .polygons([polygons]), .faceProjection([faceProjection]) set and read the corresponding options. Use .faceFind(voronoi.find) for faster results.

d3.geoCubic() Source

The cubic projection.

d3.geoDodecahedral() Source

The dodecahedral projection.

d3.geoIcosahedral() Source

The icosahedral projection.

d3.geoAirocean() Source

Buckminster Fuller’s Airocean projection (also known as “Dymaxion”), based on a very specific arrangement of the icosahedron which allows continuous continent shapes. Fuller’s triangle transformation, as formulated by Robert W. Gray (and implemented by Philippe Rivière), makes the projection almost equal-area.

d3.geoCahillKeyes() Source
d3.geoCahillKeyes

The Cahill-Keyes projection, designed by Gene Keyes (1975), is built on Bernard J. S. Cahill’s 1909 octant design. Implementation by Mary Jo Graça (2011), ported to D3 by Enrico Spinielli (2013).

d3.geoTetrahedralLee() Source
d3.geoLeeRaw

Lee’s tetrahedral conformal projection.

Default angle is +30°, apex up (-30° for base up, apex down).

Default aspect uses projection.rotate([30, 180]) and has the North Pole at the triangle’s center -- use projection.rotate([-30, 0]) for the South aspect.

d3.geoCox() Source
d3.geoCoxRaw

The Cox conformal projection.