Fibonacci sphere quasi-random radome

Uses geoVoronoi to compute triangles from a set of points on the sphere.

Antenna radomes make use of quasi-random lattices to help limiting signal degradation.

The points on the are distributed by a Fibonacci sphere algorithm. Once could probably use Poisson-disc sampling instead.

Inspiration: Trevor Paglen’s pictures of radomes at the NSA’s Menwith Hill Station in the UK.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.polygons {
  fill: #f4f4f4;
  stroke: #000;
}

.polygons.found {
  fill: #f00; 
}

.sites {
  fill: #000;
  stroke: #fff;
}

</style>
<svg width="960" height="500"></svg>
<script src="https://d3js.org/d3.v5.min.js"></script>
<script src="https://unpkg.com/d3-delaunay@5"></script>
<script src="https://unpkg.com/d3-geo-voronoi@1.5"></script>
<script>

// number of sites
  const n = 150;
  
    var radians = Math.PI / 180;
    var spherical = function (cartesian) {
        var r = Math.sqrt(cartesian[0] * cartesian[0] + cartesian[1] * cartesian[1]),
            lat = Math.atan2(cartesian[2], r),
            lng = Math.atan2(cartesian[1], cartesian[0]);
        return [lng / radians, lat / radians];
    }
    var cartesian = function (spherical) {
        var lambda = spherical[0] * radians,
            phi = spherical[1] * radians,
            cosphi = Math.cos(phi);
        return [
    cosphi * Math.cos(lambda),
    cosphi * Math.sin(lambda),
    Math.sin(phi)
  ];
    }

function fibonacci_sphere(samples=1, randomize=true){
    rnd = 1.
    if (randomize) {
        rnd = Math.random() * samples
    }

var offset = 2./samples
    var increment = Math.PI * (3. - Math.sqrt(5.));

return d3.range(samples)
    .map(function(i) {
        var y = ((i * offset) - 1) + (offset / 2),
            r = Math.sqrt(1 - Math.pow(y,2)),
            phi = ((i + rnd) % samples) * increment,
            x = Math.cos(phi) * r,
            z = Math.sin(phi) * r
        return([x,y,z])
    });
}
 var sites = fibonacci_sphere(n, false).map(spherical);
 
  
var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var color = function(t) {
return d3.hsl(280+40*t, 0.18, 0.4)
} 
  
var voronoi = d3.geoVoronoi();
 
var init = 53;

var projection = d3.geoOrthographic().rotate([init,0]);
var path = d3.geoPath()
    .projection(projection);

var diagram = voronoi(sites);

var points = svg.append("g")
    .attr("class", "points")
  .selectAll("path")
  .data(sites)
  .enter().append("path")
  .attr("d", function(d){
    return path({
      type: 'Point',
      coordinates: d
    })
  });

redraw();

if(true)
d3.interval(function(el){
  projection.rotate([init+el/30, 0]);
  redraw()
},60);
 
 
function redraw() {
  polygon = polygon.call(redrawPolygon);
}

}

</script>

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

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

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