add default depth cue params

assignment-1b/src/scene/data.rs

@@ -6,8 +6,8 @@ use nalgebra::Vector3;
 use crate::image::Color;
 use crate::ray::Ray;
 
-use super::Scene;
 use super::illumination::IntersectionContext;
+use super::Scene;
 
 pub trait ObjectKind: Debug + Send + Sync {
   /// Determine where the ray intersects this object, returning the earliest
@@ -65,7 +65,7 @@ pub struct Light {
   pub color: Vector3<f64>,
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct DepthCueing {
   pub color: Color,
   pub a_max: f64,
@@ -74,6 +74,22 @@ pub struct DepthCueing {
   pub dist_min: f64,
 }
 
+/// A default implementation here needs to simulate what would happen if there
+/// was no depth cueing. In this case, if we have both a_max and a_min be 1.0,
+/// then the original color will always apply and there will be no need for
+/// depth color
+impl Default for DepthCueing {
+  fn default() -> Self {
+    Self {
+      color: Default::default(),
+      a_max: 1.0,
+      a_min: 1.0,
+      dist_max: 0.0,
+      dist_min: 0.0,
+    }
+  }
+}
+
 impl Scene {
   /// Determine the boundaries of the viewing window in world coordinates
   pub fn compute_viewing_window(&self, distance: f64) -> Rect {