From 61b54375610fde6d75dec38a6739ab90463f4fcf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20R=C3=B6ger?= <jonas.roeger@tu-dortmund.de>
Date: Wed, 20 Nov 2024 13:42:25 +0100
Subject: [PATCH] feat(plane): add a special checkerboard plane

---
 src/bin/rt_demo.rs     | 29 +++++++++++-------
 src/raytracer/plane.rs | 67 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 85 insertions(+), 11 deletions(-)

diff --git a/src/bin/rt_demo.rs b/src/bin/rt_demo.rs
index 026ed88..7ef5fe6 100644
--- a/src/bin/rt_demo.rs
+++ b/src/bin/rt_demo.rs
@@ -1,6 +1,6 @@
 use lispers::raytracer::{
     camera::Camera,
-    plane::Plane,
+    plane::Checkerboard,
     scene::Scene,
     sphere::Sphere,
     types::{Color, Light, Material, Point3, Vector3},
@@ -12,10 +12,10 @@ use std::time::Instant;
 fn main() {
     let mut scene = Scene::new();
 
-    scene.set_ambient(Color::new(0.2, 0.2, 0.2));
+    scene.set_ambient(Color::new(0.1, 0.1, 0.1));
 
     scene.add_light(Light {
-        position: Point3::new(4.0, 7.0, 10.0),
+        position: Point3::new(5.0, 7.0, 10.0),
         color: Color::new(1.0, 1.0, 1.0),
     });
     scene.add_light(Light {
@@ -23,16 +23,25 @@ fn main() {
         color: Color::new(1.0, 1.0, 1.0),
     });
 
-    scene.add_object(Arc::new(Plane::new(
+    scene.add_object(Arc::new(Checkerboard::new(
         Point3::new(0.0, -1.0, 0.0),
         Vector3::new(0.0, 1.0, 0.0),
         Material::new(
-            Color::new(0.5, 0.5, 0.5),
-            Color::new(0.5, 0.5, 0.5),
+            Color::new(1.0, 1.0, 1.0),
+            Color::new(1.0, 1.0, 1.0),
             Color::new(0.0, 0.0, 0.0),
             0.0,
-            0.6,
+            0.5,
         ),
+        Material::new(
+            Color::new(0.0, 0.0, 0.0),
+            Color::new(0.0, 0.0, 0.0),
+            Color::new(0.0, 0.0, 0.0),
+            0.0,
+            0.5,
+        ),
+        0.3,
+        Vector3::new(0.0, 0.0, 1.0),
     )));
 
     scene.add_object(Arc::new(Sphere::new(
@@ -76,14 +85,14 @@ fn main() {
         Point3::new(-1.0, -0.5, 0.0),
         Vector3::new(0.0, 1.0, 0.0),
         60.0,
-        4 * 256,
-        3 * 256,
+        4 * 512,
+        3 * 512,
     );
 
     let fname = "demo-scene.png";
     print!("Rendering demo scene...");
     let start = Instant::now();
-    match camera.render(&scene, 5, 3).save(fname) {
+    match camera.render(&scene, 10, 4).save(fname) {
         Ok(_) => {
             println!(" finished ({}s) ", start.elapsed().as_secs_f32());
             println!("Image saved to {}", fname)
diff --git a/src/raytracer/plane.rs b/src/raytracer/plane.rs
index 5501663..90e05fa 100644
--- a/src/raytracer/plane.rs
+++ b/src/raytracer/plane.rs
@@ -1,4 +1,4 @@
-use super::types::{Intersect, Material, Point3, Vector3};
+use super::types::{Intersect, Material, Point3, Scalar, Vector3};
 
 extern crate nalgebra as na;
 
@@ -12,6 +12,18 @@ pub struct Plane {
     material: Material,
 }
 
+/// A infinite checkerboard plane in 3D space.
+pub struct Checkerboard {
+    /// The base plane containing the "white" material
+    base: Plane,
+    /// An alternative "black" material
+    material_alt: Material,
+    /// The scale of the checkerboard (side-length of each square)
+    scale: f64,
+    /// A projection matrix to map 3D points to the 2D plane space.
+    projection_matrix: na::Matrix2x3<Scalar>,
+}
+
 impl Plane {
     /// Create a new plane.
     /// - `position` is the position of the plane.
@@ -26,6 +38,32 @@ impl Plane {
     }
 }
 
+impl Checkerboard {
+    /// Create a new Checkerboard Plane.
+    /// - `position` is the position of the plane.
+    /// - `normal` is the normal of the plane.
+    /// - `material1` is the material of the "white" squares.
+    /// - `material2` is the material of the "black" squares.
+    /// - `scale` is the side-length of each square.
+    /// - `up` is "y" direction on the plane in 3D-Space.
+    pub fn new(
+        position: Point3,
+        normal: Vector3,
+        material1: Material,
+        material2: Material,
+        scale: f64,
+        up: Vector3,
+    ) -> Checkerboard {
+        let right = up.cross(&normal).normalize();
+        Checkerboard {
+            base: Plane::new(position, normal, material1),
+            material_alt: material2,
+            scale,
+            projection_matrix: na::Matrix3x2::from_columns(&[right, up]).transpose(),
+        }
+    }
+}
+
 impl Intersect for Plane {
     fn intersect<'a>(
         &'a self,
@@ -49,3 +87,30 @@ impl Intersect for Plane {
         None
     }
 }
+
+impl Intersect for Checkerboard {
+    fn intersect<'a>(
+        &'a self,
+        ray: &super::types::Ray,
+    ) -> Option<(
+        Point3,
+        Vector3,
+        super::types::Scalar,
+        &'a super::types::Material,
+    )> {
+        if let Some((point, normal, t, material)) = self.base.intersect(ray) {
+            let v3 = point - self.base.position;
+            let v2 = self.projection_matrix * v3;
+
+            if ((v2.x / self.scale).round() % 2.0 == 0.0)
+                == ((v2.y / self.scale).round() % 2.0 == 0.0)
+            {
+                Some((point, normal, t, material))
+            } else {
+                Some((point, normal, t, &self.material_alt))
+            }
+        } else {
+            None
+        }
+    }
+}