edge

简介

Polygon的edge是表示多边形边缘的类，可用于计算多边形的周长、交点等操作。

API

构造函数

new Polygon.Edge(v1, v2);

• v1：起始点
• v2：结束点

实例方法

length()

计算边缘长度。

let edge = new Polygon.Edge({ x: 0, y: 0 }, { x: 3, y: 4 });
let length = edge.length(); // 返回5

intersectsWithRay(ray)

计算边缘是否与射线相交。

let edge = new Polygon.Edge({ x: 0, y: 0 }, { x: 5, y: 0 });
let ray = new Polygon.Ray({ x: 2, y: 2 }, { x: 1, y: 0 });
let intersects = edge.intersectsWithRay(ray); // 返回true

• ray：射线对象，包含origin（起点）和direction（方向）属性

getIntersectionWithEdge(edge)

计算当前边缘与另一个边缘的交点。

let edge1 = new Polygon.Edge({ x: 0, y: 0 }, { x: 5, y: 0 });
let edge2 = new Polygon.Edge({ x: 2, y: 2 }, { x: 2, y: -2 });
let intersection = edge1.getIntersectionWithEdge(edge2); // 返回{ x: 2, y: 0 }

• edge：另一个边缘对象

示例

// 计算三角形周长
let p1 = { x: 0, y: 0 };
let p2 = { x: 3, y: 0 };
let p3 = { x: 0, y: 4 };
let edge1 = new Polygon.Edge(p1, p2);
let edge2 = new Polygon.Edge(p2, p3);
let edge3 = new Polygon.Edge(p3, p1);
let perimeter = edge1.length() + edge2.length() + edge3.length(); // 返回12

// 计算多边形交点
let polygon1 = new Polygon([{ x: 0, y: 0 }, { x: 5, y: 0 }, { x: 2, y: 3 }]);
let polygon2 = new Polygon([{ x: 1, y: 2 }, { x: 4, y: 2 }, { x: 2, y: -1 }]);
let intersections = [];
for (let edge1 of polygon1.edges) {
  for (let edge2 of polygon2.edges) {
    let intersection = edge1.getIntersectionWithEdge(edge2);
    if (intersection) {
      intersections.push(intersection);
    }
  }
}
console.log(intersections); // 打印出[{ x: 2, y: 1 }]  

参考链接

• Polygon.js官方文档 - Edge