From 6037fe2802621b0d449e440bcffe3da674d24ae1 Mon Sep 17 00:00:00 2001
From: Ishan Jain <contact@ishanjain.me>
Date: Tue, 2 Mar 2021 18:29:01 +0530
Subject: [PATCH] Added checkered texture

---
 src/demo.rs                 |  7 +++++--
 src/materials/lambertian.rs |  5 ++++-
 src/texture/checker.rs      | 24 ++++++++++++++++++++++++
 src/texture/mod.rs          |  4 +++-
 src/texture/solid.rs        |  4 ++--
 5 files changed, 38 insertions(+), 6 deletions(-)
 create mode 100644 src/texture/checker.rs

diff --git a/src/demo.rs b/src/demo.rs
index 36c8b46..4b29897 100644
--- a/src/demo.rs
+++ b/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;
diff --git a/src/materials/lambertian.rs b/src/materials/lambertian.rs
index a304011..9645e0d 100644
--- a/src/materials/lambertian.rs
+++ b/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))
     }
 }
diff --git a/src/texture/checker.rs b/src/texture/checker.rs
new file mode 100644
index 0000000..2741449
--- /dev/null
+++ b/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)
+        }
+    }
+}
diff --git a/src/texture/mod.rs b/src/texture/mod.rs
index d3ded52..f3dba8e 100644
--- a/src/texture/mod.rs
+++ b/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);
 }
diff --git a/src/texture/solid.rs b/src/texture/solid.rs
index 48d7438..7d8f04e 100644
--- a/src/texture/solid.rs
+++ b/src/texture/solid.rs
@@ -11,7 +11,7 @@ impl Solid {
 }
 
 impl Texture for Solid {
-    fn value(&self, _u: f64, _v: f64) -> Vec3 {
-        self.color
+    fn value(&self, _u: f64, _v: f64, p: &mut Vec3) {
+        *p = self.color
     }
 }