lr-core/utils/dda.js

Line Rider core library

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = dda;
// digital differential analyzer
function dda(x0, y0, x1, y1) {
  if (x0 > x1) {
    return dda(x1, y1, x0, y0);
  }
  const slope = (y1 - y0) / (x1 - x0);
  if (Math.abs(slope) > 1) {
    return dda(y0, x0, y1, x1).map(({ x, y }) => ({ x: y, y: x }));
  }
  const cx0 = Math.floor(x0);
  const cy0 = Math.floor(y0);
  const cx1 = Math.floor(x1);
  const cy1 = Math.floor(y1);

  let out = [{ x: cx0, y: cy0 }];
  let prevY = cy0;
  for (let x = cx0 + 1; x <= cx1; x++) {
    const y = Math.floor(y1 + slope * (x - x1));
    if (y !== prevY) {
      out.push({ x: x - 1, y });
      prevY = y;
    }
    out.push({ x, y });
  }
  if (cy1 !== prevY) {
    out.push({ x: cx1, y: cy1 });
  }

  return out;
}