public function LineString::lineSegmentIntersect in geoPHP 8

Same name and namespace in other branches

1. 7 geoPHP/lib/geometry/LineString.class.php \LineString::lineSegmentIntersect()

File

geoPHP/lib/geometry/LineString.class.php, line 160

Class

LineString

LineString. A collection of Points representing a line. A line can have more than one segment.

Code

public function lineSegmentIntersect($segment) {
  $p0_x = $this
    ->startPoint()
    ->x();
  $p0_y = $this
    ->startPoint()
    ->y();
  $p1_x = $this
    ->endPoint()
    ->x();
  $p1_y = $this
    ->endPoint()
    ->y();
  $p2_x = $segment
    ->startPoint()
    ->x();
  $p2_y = $segment
    ->startPoint()
    ->y();
  $p3_x = $segment
    ->endPoint()
    ->x();
  $p3_y = $segment
    ->endPoint()
    ->y();
  $s1_x = $p1_x - $p0_x;
  $s1_y = $p1_y - $p0_y;
  $s2_x = $p3_x - $p2_x;
  $s2_y = $p3_y - $p2_y;
  $fps = -$s2_x * $s1_y + $s1_x * $s2_y;
  $fpt = -$s2_x * $s1_y + $s1_x * $s2_y;
  if ($fps == 0 || $fpt == 0) {
    return FALSE;
  }
  $s = (-$s1_y * ($p0_x - $p2_x) + $s1_x * ($p0_y - $p2_y)) / $fps;
  $t = ($s2_x * ($p0_y - $p2_y) - $s2_y * ($p0_x - $p2_x)) / $fpt;
  if ($s > 0 && $s < 1 && $t > 0 && $t < 1) {

    // Collision detected
    return TRUE;
  }
  return FALSE;
}