1 files changed, 17 insertions, 4 deletions
diff --git a/src/renderer.rs b/src/renderer.rs
index 14dfb6f..c523268 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -38,6 +38,20 @@ fn render_circle<P: Pixel>(layer: &mut TileLayer<P>, center: (u64, u64), radius:
     }
 }
 
+fn direction_vector(a: (u64, u64), b: (u64, u64)) -> Vector2<f64> {
+    let dx = if b.0 > a.0 {
+        (b.0 - a.0) as f64
+    } else {
+        -((a.0 - b.0) as f64)
+    };
+    let dy = if b.1 > a.1 {
+        (b.1 - a.1) as f64
+    } else {
+        -((a.1 - b.1) as f64)
+    };
+    vector![dx, dy]
+}
+
 fn render_line<P: Pixel>(
     layer: &mut TileLayer<P>,
     start: (u64, u64),
@@ -58,16 +72,15 @@ fn render_line<P: Pixel>(
             a[0] + b[0] as u64
         };
         let y = if b[1] < 0 {
-            a[1] - b[0].abs() as u64
+            a[1] - b[1].abs() as u64
         } else {
             a[1] + b[1] as u64
         };
         vector![x, y]
     }
 
-    let r = vector![end.0 as f64, end.1 as f64] - vector![start.0 as f64, start.1 as f64];
-    let r = r.normalize();
-    let normal = vector![r[1], -r[0]];
+    let r = direction_vector(start, end);
+    let normal = vector![r[1], -r[0]].normalize();
 
     let start = vector![start.0, start.1];
     let end = vector![end.0, end.1];