geoVoronoi Delaunay links and Urquhart graph

by Philippe Rivière.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
    #sphere {
        fill: #fff;
        stroke: #444;
        stroke-width: 2;
    }
    .polygons {
        stroke: #444;
    }

.links {
        stroke: white;
        stroke-width: 2.5;
        fill: none;
    }

.links .secondary {
        stroke-width: .5;
        stroke-dasharray: 3 1;
    }
    
    .sites {
        stroke: black;
        fill: white;
    }
    
    #legend {
        position: absolute;
        top: 15;
        left: 15;
        font-family: sans-serif;
    }
</style>
<div id="legend">
Delaunay links<br>
Urquart graph in bold
</div>
<svg width="960" height="600"></svg>

var points = {
    type: "FeatureCollection",
    features: d3.range(100).map(function() {
        return {
            type: "Point",
            coordinates: [ 360 * Math.random(), 90 * (Math.random() - Math.random()) ]
        }
    })
}

var v = d3.geoVoronoi()(points);

var projection = d3.geoOrthographic(),
    path = d3.geoPath().projection(projection);

var svg = d3.select("svg");

svg.append('path')
    .attr('id', 'sphere')
    .datum({ type: "Sphere" })
    .attr('d', path);

svg.append('g')
    .attr('class', 'polygons')
    .selectAll('path')
    .data(v.polygons().features)
    .enter()
    .append('path')
    .attr('d', path)
  .attr('fill', function(_,i) { return d3.schemeCategory10[i%10]; });

svg.append('g')
    .attr('class', 'links')
    .selectAll('path')
    .data(v.links().features)
    .enter()
    .append('path')
    .classed('secondary', function(d) {
        return !d.properties.urquhart;
    })
    .attr('d', path);

svg.append('g')
    .attr('class', 'sites')
    .selectAll('path')
    .data(points.features)
    .enter()
    .append('path')
    .attr('d', path);

// gentle animation
if(false)d3.interval(function(elapsed) {
    projection.rotate([ elapsed / 150, 0 ]);
    svg.selectAll('path')
        .attr('d', path);
}, 50);

</script>

https://d3js.org/d3.v5.min.js

https://unpkg.com/d3-delaunay@5

https://unpkg.com/d3-geo-voronoi@1.5