The Delaunay.hullPolygon() Method returns the closed polygon [[x0, y0], [x1, y1], …, [x0, y0]] representing the convex hull.
Syntax:
Delaunay.hullPolygon()
Parameters:
This method takes no parameters.
Return Value:
This method returns an Array of polygons that represents a convex hull.
Example 1: The below code example shows the use of the d3.Delaunay.hullPolygon() method.
HTML
<!DOCTYPE html> < html >
< head >
< meta charset = "utf-8" >
</ head >
< body style = "text-align: center;" >
< h1 style = "text-align: center; color: green;" >
GeeksforGeeks
</ h1 >
< h3 style = "text-align: center;" >
D3.js | d3.hullPolygon() Method
</ h3 >
< div id = "app" style=
"text-align: center;
margin-top: 20px;
font-size: 18px;">
</ div >
< script type = "module" >
import * as d3 from "https://cdn.skypack.dev/d3@7";
const canvasWidth = 400;
const canvasHeight = 300;
const canvas =
document.createElement("canvas");
const context = canvas.getContext("2d");
canvas.width = canvasWidth;
canvas.height = canvasHeight;
const data = Array(50).fill()
.map((_, i) => ({
x: (i * canvasWidth) / 50,
y: Math.random() * canvasHeight
}));
const voronoi = d3.Delaunay.from(data,
(d) => d.x,
(d) => d.y
).voronoi([0, 0, canvasWidth, canvasHeight]);
context.clearRect(0, 0, canvasWidth, canvasHeight);
context.fillStyle = "black";
context.beginPath();
voronoi.delaunay.renderPoints(context, 1);
context.fill();
context.lineWidth = 1.5;
const segments =
voronoi.render().split(/M/).slice(1);
for (const e of segments) {
context.beginPath();
context.strokeStyle =
d3.hsl(360 * Math.random(), 0.7, 0.5);
context.stroke(new Path2D("M" + e));
}
const hull = voronoi.delaunay.hullPolygon();
document.querySelector("#app").innerHTML =
`Convex Hull: ${JSON.stringify(hull)}`;
document.querySelector("#app").
appendChild(canvas);
</ script >
</ body >
</ html >
|
Output:
Example 2: The below code demonstrates the use of D3.js HullPloygon() method to calculate the convex hull of a set of points.
HTML
<!DOCTYPE html> < html >
< head >
< meta charset = "utf-8" >
</ head >
< body style = "text-align: center;" >
< h1 style = "text-align: center; color: green;" >
GeeksforGeeks
</ h1 >
< h3 style = "text-align: center;" >
D3.js | hullPolygon() Method
</ h3 >
< div id = "app" style=
"text-align: center;
margin-top: 20px;">
</ div >
< script type = "module" >
import * as d3 from "https://cdn.skypack.dev/d3@7";
const width = 600;
const height = 400;
const points = Array.from({ length: 50 },
() => [Math.random() * width,
Math.random() * height]);
const delaunay = d3.Delaunay.from(points);
const hull = delaunay.hullPolygon();
const canvas = d3.select("#app")
.append("canvas")
.attr("width", width)
.attr("height", height);
const context =
canvas.node().getContext("2d");
context.beginPath();
delaunay.renderPoints(context);
context.fillStyle = "black";
context.fill();
context.beginPath();
context.strokeStyle = "blue";
context.lineWidth = 2;
context.moveTo(hull[0][0], hull[0][1]);
for (const point of hull) {
context.lineTo(point[0], point[1]);
}
context.closePath();
context.stroke();
</ script >
</ body >
</ html >
|
Output:
Recommended Articles