Use CheckerTexture for ground in book scene.

rtiow/src/scenes/book.rs

@@ -11,7 +11,9 @@ use material::Metal;
 use renderer::Opt;
 use renderer::Scene;
 use sphere::Sphere;
+use texture::CheckerTexture;
 use texture::ConstantTexture;
+use texture::Texture;
 use vec3::Vec3;
 
 pub fn new(opt: &Opt) -> Scene {
@@ -51,14 +53,22 @@ pub fn new(opt: &Opt) -> Scene {
     }
 }
 
-fn random_scene(background_color: Vec3) -> Vec<Box<Hit>> {
+fn random_scene(ground_color: Vec3) -> Vec<Box<Hit>> {
     let mut rng = rand::thread_rng();
+    let checker = true;
+    let ground_texture: Box<Texture> = if checker {
+        Box::new(CheckerTexture::new(
+            Box::new(ConstantTexture::new(Vec3::new(0., 0., 0.))),
+            Box::new(ConstantTexture::new(ground_color)),
+        ))
+    } else {
+        Box::new(ConstantTexture::new(ground_color))
+    };
+
     let mut objects: Vec<Box<Hit>> = vec![Box::new(Sphere::new(
         Vec3::new(0., -1000., 0.),
         1000.,
-        Box::new(Lambertian::new(Box::new(ConstantTexture::new(
-            background_color,
-        )))),
+        Box::new(Lambertian::new(ground_texture)),
     ))];
     let mut random = || rng.gen_range::<f32>(0., 1.);