diff --git a/rtiow/src/renderer.rs b/rtiow/src/renderer.rs
index c697b33..72ac4e9 100644
--- a/rtiow/src/renderer.rs
+++ b/rtiow/src/renderer.rs
@@ -236,6 +236,16 @@ enum Response {
         pixels: Vec<Vec3>,
     },
 }
+fn render_pixel(scene: &Scene, x: usize, y: usize) -> Vec3 {
+    let mut pixel: Vec3 = Default::default();
+    for _ in 0..scene.subsamples {
+        pixel = pixel + trace_pixel(x, y, scene);
+    }
+    pixel = pixel / scene.subsamples as f32;
+    // Gamma correct, use gamma 2 correction, which is 1/gamma where gamma=2 which is 1/2 or
+    // sqrt.
+    Vec3::new(pixel[0].sqrt(), pixel[1].sqrt(), pixel[2].sqrt())
+}
 
 fn render_worker(
     tid: usize,
@@ -245,19 +255,14 @@ fn render_worker(
 ) {
     for req in input_chan {
         match req {
+            Request::Line { width, y } => {
+                let pixels = (0..width).map(|x| render_pixel(scene, x, y)).collect();
+                output_chan.send(Response::Line { width, y, pixels });
+            }
             Request::Pixel { x, y } => {
-                let mut pixel: Vec3 = Default::default();
-                for _ in 0..scene.subsamples {
-                    pixel = pixel + trace_pixel(x, y, scene);
-                }
-                pixel = pixel / scene.subsamples as f32;
-                // Gamma correct, use gamma 2 correction, which is 1/gamma where gamma=2 which is 1/2 or
-                // sqrt.
-                let pixel = Vec3::new(pixel[0].sqrt(), pixel[1].sqrt(), pixel[2].sqrt());
-
+                let pixel = render_pixel(scene, x, y);
                 output_chan.send(Response::Pixel { x, y, pixel });
             }
-            _ => unimplemented!("Only Pixel requests are implemented"),
         }
     }
     trace!(target: "renderer", "Shutting down worker {}", tid);
@@ -283,10 +288,16 @@ pub fn render(scene: Scene, output_dir: &Path) -> std::result::Result<(), std::i
 
     let (w, h) = (scene.width, scene.height);
     thread::spawn(move || {
-        // TODO(wathiede): handle sending Line requests for optimization.
-        for y in 0..w {
-            for x in 0..h {
-                pixel_req_tx.send(Request::Pixel { x, y });
+        let batch_by_line = true;
+        if batch_by_line {
+            for y in 0..h {
+                pixel_req_tx.send(Request::Line { width: w, y });
+            }
+        } else {
+            for y in 0..h {
+                for x in 0..w {
+                    pixel_req_tx.send(Request::Pixel { x, y });
+                }
             }
         }
         drop(pixel_req_tx);
@@ -295,8 +306,9 @@ pub fn render(scene: Scene, output_dir: &Path) -> std::result::Result<(), std::i
     println!("Rendering with {} subsamples", scene.subsamples);
     let mut img = RgbImage::new(scene.width as u32, scene.height as u32);
     let total = scene.width * scene.height;
+    let mut cur_pixel = 0;
     let mut last_progress = 1000;
-    for (i, resp) in pixel_resp_rx.iter().enumerate() {
+    for resp in pixel_resp_rx {
         match resp {
             Response::Pixel { x, y, pixel } => {
                 let y_inv = scene.height - y - 1;
@@ -309,7 +321,7 @@ pub fn render(scene: Scene, output_dir: &Path) -> std::result::Result<(), std::i
                         (pixel[2] * 255.).min(255.) as u8,
                     ]),
                 );
-                let progress = 100 * i / total;
+                let progress = 100 * cur_pixel / total;
                 if progress != last_progress {
                     last_progress = progress;
                     if progress % 10 == 0 {
@@ -319,8 +331,37 @@ pub fn render(scene: Scene, output_dir: &Path) -> std::result::Result<(), std::i
                     }
                     io::stdout().flush().unwrap();
                 }
+                cur_pixel += 1;
+            }
+            Response::Line {
+                width: _,
+                y,
+                pixels,
+            } => {
+                for (x, pixel) in pixels.iter().enumerate() {
+                    let y_inv = scene.height - y - 1;
+                    img.put_pixel(
+                        x as u32,
+                        y_inv as u32,
+                        image::Rgb([
+                            (pixel[0] * 255.).min(255.) as u8,
+                            (pixel[1] * 255.).min(255.) as u8,
+                            (pixel[2] * 255.).min(255.) as u8,
+                        ]),
+                    );
+                    let progress = 100 * cur_pixel / total;
+                    if progress != last_progress {
+                        last_progress = progress;
+                        if progress % 10 == 0 {
+                            print!("{}%", progress);
+                        } else {
+                            print!(".");
+                        }
+                        io::stdout().flush().unwrap();
+                    }
+                    cur_pixel += 1;
+                }
             }
-            _ => unimplemented!("Only Pixel responses are implemented"),
         }
     }
     println!();