diff --git a/src/bin/viewer.rs b/src/bin/viewer.rs
index 92d6a9c..300a626 100644
--- a/src/bin/viewer.rs
+++ b/src/bin/viewer.rs
@@ -110,8 +110,6 @@ fn main() {
     let loader = Loader::new(opt.directory);
     let mut viewer = Viewer::default();
     viewer.loader = loader;
-    //let frame = loader.load_next(None);
-    //viewer.switch_frame(frame.unwrap());
 
     // disable line buffering
     crossterm::terminal::enable_raw_mode().unwrap();
@@ -128,6 +126,6 @@ fn main() {
             _ => {},
         }
     }
-    // otherwise terminal is left in a wacky state
+    // return the terminal to its original state
     crossterm::terminal::disable_raw_mode().unwrap();
 }
diff --git a/src/render.rs b/src/render.rs
index 164cc05..9f9f80e 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -76,8 +76,13 @@ struct RenderSteps<'a> {
 }
 
 impl<'a> RenderSteps<'a> {
+    /// Render using default configuration constants
     fn render(state: &'a dyn GenericSim, measurements: &'a [Box<dyn AbstractMeasurement>], z: u32) -> RgbImage {
-        let (width, height) = im_size(state, 640, 480);
+        Self::render_configured(state, measurements, z, (640, 480))
+    }
+    /// Render, controlling things like the size.
+    fn render_configured(state: &'a dyn GenericSim, measurements: &'a [Box<dyn AbstractMeasurement>], z: u32, max_size: (u32, u32)) -> RgbImage {
+        let (width, height) = im_size(state, max_size.0, max_size.1);
         trace!("rendering at {}x{} with z={}", width, height, z);
         let mut me = Self::new(state, measurements, width, height, z);
         me.render_scalar_field(10.0,  false, 2, |cell| {
@@ -274,8 +279,9 @@ pub trait Renderer: Send + Sync {
 pub struct ColorTermRenderer;
 
 impl Renderer for ColorTermRenderer {
-    fn render_with_image(&self, _state: &dyn GenericSim, im: &RgbImage) {
-        // TODO: should scale the image to the size of the terminal!
+    fn render_z_slice(&self, state: &dyn GenericSim, z: u32, measurements: &[Box<dyn AbstractMeasurement>]) {
+        let max_size = crossterm::terminal::size().unwrap();
+        let im = RenderSteps::render_configured(state, measurements, z, (max_size.0 as _, max_size.1 as _));
         let mut stdout = std::io::stdout();
         let (w, h) = crossterm::terminal::size().unwrap();
         stdout.queue(cursor::MoveTo(0, 0));