Line intersect - Node.js Geometry

Node.js examples for Geometry:Line

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Description

Line intersect

Demo Code



/*/*from   w  w  w  .jav  a2s .  c om*/
 * @param x1, y1, x2, y2    set of number coordinates for the second line
 * @param x3, y3, x4, y4    set of number coordinates for the second line
 * @return          boolean whether the two passed lines cross
 */
function line_intersect(x1, y1, x2, y2, x3, y3, x4, y4) {
  var x = ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) / ((x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4));
  var y = ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) / ((x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4));

  if (isNaN(x) || isNaN(y)) {
    return false;
  } else {
    if (x1 >= x2) {
      if (!(x2 <= x && x <= x1)) {
        return false;
      }
    } else {
      if (!(x1 <= x && x <= x2)) {
        return false;
      }
    }
    if (y1 >= y2) {
      if (!(y2 <= y && y <= y1)) {
        return false;
      }
    } else {
      if (!(y1 <= y && y <= y2)) {
        return false;
      }
    }
    if (x3 >= x4) {
      if (!(x4 <= x && x<= x3)) {
        return false;
      }
    } else {
      if (!(x3 <= x && x <= x4)) {
        return false;
      }
    }
    if (y3 >= y4) {
      if (!(y4 <= y && y <= y3)) {
        return false;
      }
    } else {
      if (!(y3 <= y && y <= y4)) {
        return false;
      }
    }
  }
  return true;
}

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