Use clockwise algorithm for line segment intersection checks (resolves …

…#12)

rust/src/geometry.rs

@@ -162,6 +162,11 @@ impl LineSegment {
 		}
 	}
 
+	pub fn intersects(&self, other: &LineSegment) -> bool {
+		is_clockwise(self.p1, other.p1, other.p2) != is_clockwise(self.p2, other.p1, other.p2)
+			&& is_clockwise(self.p1, self.p2, other.p1) != is_clockwise(self.p1, self.p2, other.p2)
+	}
+
 	pub fn intersection(&self, other: &LineSegment) -> Option<Point> {
 		let intersection = self.line.intersection(&other.line);
 		intersection.filter(|intersection| {
@@ -192,6 +197,10 @@ impl LineSegment {
 	}
 }
 
+fn is_clockwise(a: Point, b: Point, c: Point) -> bool {
+	(c.y - a.y) * (b.x - a.x) <= (b.y - a.y) * (c.x - a.x)
+}
+
 pub fn between<T: Copy + PartialOrd>(num: T, a: T, b: T) -> bool {
 	let (min, max) = if a < b { (a, b) } else { (b, a) };
 	num >= min && num <= max

rust/src/pathfinder.rs

@@ -161,9 +161,6 @@ impl Pathfinder {
 	}
 
 	fn collides_with_wall(line: &LineSegment, wall: &LineSegment) -> bool {
-		if !line.bounding_rect().intersects(&wall.bounding_rect()) {
-			return false;
-		}
-		line.intersection(wall).is_some()
+		line.intersects(wall)
 	}
 }