Added checkered texture

src/demo.rs

@@ -1,7 +1,7 @@
 use crate::{
     materials::{Dielectric, Lambertian, Metal},
     shapes::{MovingSphere, Sphere},
-    texture::Solid,
+    texture::{Checker, Solid},
     types::{Ray, Vec3},
     BvhNode, Camera, Hitable, HORIZONTAL_PARTITION, VERTICAL_PARTITION,
 };
@@ -55,7 +55,10 @@ impl Demo {
         world.push(Arc::new(Sphere::new(
             Vec3::new(0.0, -1000.0, 0.0),
             1000.0,
-            Lambertian::new(Solid::new(Vec3::new(0.5, 0.5, 0.5))),
+            Lambertian::new(Checker::new(
+                Solid::new(Vec3::new(0.2, 0.3, 0.1)),
+                Solid::new(Vec3::new(0.9, 0.9, 0.9)),
+            )),
         )));
 
         let radius = 0.2;

src/materials/lambertian.rs

@@ -21,6 +21,9 @@ impl<T: Texture + Send + Sync> Material for Lambertian<T> {
         let scatter_direction = hit_rec.normal + random_point_in_unit_sphere(rng);
         let scattered_ray = Ray::new(hit_rec.p, scatter_direction, ray.time());
 
-        (self.albedo.value(hit_rec.u, hit_rec.v), Some(scattered_ray))
+        let mut p = hit_rec.p;
+        self.albedo.value(hit_rec.u, hit_rec.v, &mut p);
+
+        (p, Some(scattered_ray))
     }
 }

src/texture/checker.rs

@@ -0,0 +1,24 @@
+use crate::{types::Vec3, Texture};
+
+pub struct Checker<T: Texture> {
+    odd: T,
+    even: T,
+}
+
+impl<T: Texture> Checker<T> {
+    pub fn new(even: T, odd: T) -> Self {
+        Self { odd, even }
+    }
+}
+
+impl<T: Texture> Texture for Checker<T> {
+    fn value(&self, u: f64, v: f64, p: &mut Vec3) {
+        let sine_wave = f64::sin(10.0 * p.x()) * f64::sin(10.0 * p.y()) * f64::sin(10.0 * p.z());
+
+        if sine_wave < 0.0 {
+            self.odd.value(u, v, p)
+        } else {
+            self.even.value(u, v, p)
+        }
+    }
+}

src/texture/mod.rs

@@ -1,9 +1,11 @@
+mod checker;
 mod solid;
 
+pub use checker::Checker;
 pub use solid::Solid;
 
 use crate::types::Vec3;
 
 pub trait Texture {
-    fn value(&self, u: f64, v: f64) -> Vec3;
+    fn value(&self, u: f64, v: f64, p: &mut Vec3);
 }

src/texture/solid.rs

@@ -11,7 +11,7 @@ impl Solid {
 }
 
 impl Texture for Solid {
-    fn value(&self, _u: f64, _v: f64) -> Vec3 {
+    fn value(&self, _u: f64, _v: f64, p: &mut Vec3) {
-        self.color
+        *p = self.color
     }
 }