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 line = d3.line();
var polygon = svg.append("g")
.attr("class", "polygons")
.selectAll("path")
.data(voronoi.triangles(sites).features)
.enter().append("path")
.attr("d", function(d) {
return line(d.geometry.coordinates[0].map(projection))
})
.each(function(d){
var p = d.geometry.coordinates[0][0].slice();
p[0] += projection.rotate()[0]
var c = cartesian(p);
d.depth = c[0];
})
.sort(function(a,b){ return d3.ascending(a.depth, b.depth);})
.each(function(d, i) {
var k = Math.PI * i/sites.length;
d.fill = color((1+Math.cos(k))/2);
})
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);
}
function redrawPolygon(polygon) {
polygon
.each(function(d) {
var p = d.geometry.coordinates[0][0].slice();
p[0] += projection.rotate()[0]
d.cartesian = cartesian(p);
})
.attr('fill', function(d) {
var color = d.fill,
c = d.cartesian,
t = (2.2 -2.*c[1] -1.4*c[2])/6;
return d3.interpolate('white', color)(t);
})
.attr('stroke', function(d) {
var c = d.cartesian,
t = 0.2+(2.2 -2.*c[1] -1.4*c[2])/7;
return d3.interpolate('white', 'black')(t);
});
points
.attr('fill', function(d) {
var p = d.slice();
p[0] += projection.rotate()[0];
var c = cartesian(p),
t = (2.2 -2.*c[1] -1.4*c[2])/6;
return d3.interpolate('#eee', '#334')(t);
})
}
</script>