calculating the point of intersection of two lines

Question

I have dynamically generated lines that animate and I want to detect when a lines hits another. I\'m trying to implement some basic linear algebra to obtain the equation of

Answer 1

There is an npm module that does just that: line-intersect.

Install it using

npm install --save line-intersect

ES6 usage:

import { checkIntersection } from "line-intersect";

const result = lineIntersect.checkIntersection(
  line1.start.x, line1.start.y, line1.end.x, line1.end.y,
  line2.start.x, line2.start.y, line2.end.x, line2.end.y
);

result.type  // any of "none", "parallel", "colinear", "intersecting"
result.point // only exists when result.type == 'intersecting'

If you're using typescript, here are the typings:

declare module "line-intersect" {
  export function checkIntersection(
    x1: number, y1: number,
    x2: number, y2: number,
    x3: number, y3: number,
    x4: number, y4: number): {
        type: string,
        point: {x:number, y:number}
    }; 
}

Put it in a file and reference if in tsconfig.json's "files" section.