@phaserjs/phaser/geom/intersects/GetLineToCircle.js

Phaser 4

/**
 * @author       Florian Vazelle
 * @author       Geoffrey Glaive
 * @copyright    2020 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */
import { LineToCircle } from "./LineToCircle";
import { Vec2 } from "../../math/vec2/Vec2";
export function GetLineToCircle(line, circle, out = []) {
  if (LineToCircle(line, circle)) {
    const { x1, y1, x2, y2 } = line;
    const cr = circle.radius;
    const lDirX = x2 - x1;
    const lDirY = y2 - y1;
    const oDirX = x1 - circle.x;
    const oDirY = y1 - circle.y;
    const coefficientA = lDirX * lDirX + lDirY * lDirY;
    const coefficientB = 2 * (lDirX * oDirX + lDirY * oDirY);
    const coefficientC = oDirX * oDirX + oDirY * oDirY - cr * cr;
    const lambda = coefficientB * coefficientB - 4 * coefficientA * coefficientC;
    let x;
    let y;
    if (lambda === 0) {
      const root = -coefficientB / (2 * coefficientA);
      x = x1 + root * lDirX;
      y = y1 + root * lDirY;
      if (root >= 0 && root <= 1) {
        out.push(new Vec2(x, y));
      }
    } else if (lambda > 0) {
      const root1 = (-coefficientB - Math.sqrt(lambda)) / (2 * coefficientA);
      x = x1 + root1 * lDirX;
      y = y1 + root1 * lDirY;
      if (root1 >= 0 && root1 <= 1) {
        out.push(new Vec2(x, y));
      }
      const root2 = (-coefficientB + Math.sqrt(lambda)) / (2 * coefficientA);
      x = x1 + root2 * lDirX;
      y = y1 + root2 * lDirY;
      if (root2 >= 0 && root2 <= 1) {
        out.push(new Vec2(x, y));
      }
    }
  }
  return out;
}