implement rays, lots of new stuff

src/color.rs

@@ -0,0 +1,6 @@
+use std::io::Write;
+use super::Color;
+
+pub fn write_color(out: &mut impl Write, pixel_color: Color) {
+    write!(out, "{} {} {}\n", (255.999*pixel_color.x()) as u32, (255.999*pixel_color.y()) as u32, (255.999*pixel_color.z()) as u32).unwrap();
+}

src/main.rs

@@ -1,28 +1,79 @@
 mod vec3;
+mod color;
+mod ray;
 use vec3::Vec3;
+use vec3::Color;
+use vec3::Point3;
+use ray::Ray;
+use std::env;
+use std::fs::File;
+use std::io::BufWriter;
+use std::io::Write;
+
+fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> f64 {
+    let oc = r.origin() - *center;
+    let a = Vec3::dot(r.direction(), r.direction());
+    let b = 2.0 * Vec3::dot(oc, r.direction());
+    let c = Vec3::dot(oc, oc) - radius*radius;
+    let discriminant = b*b - 4.0*a*c;
+
+    if discriminant < 0.0 {
+        return -1.0;
+    } else {
+        return (-b - discriminant.sqrt()) / (2.0*a);
+    }
+}
+
+fn ray_color(r: &Ray) -> Color{
+    let t = hit_sphere(&Point3::new(0.0, 0.0, -1.0), 0.5, r);
+    if t > 0.0 {
+        let n = Vec3::unit_vector(r.at(t) - Vec3::new(0.0, 0.0, -1.0));
+        return 0.5*Color::new(n.x()+1.0, n.y()+1.0, n.z()+1.0);
+    }
+    
+    let unit_direction = r.direction();
+    let t = 0.5*(unit_direction.y() + 1.0);
+    return (1.0-t)*Color::new(1.0,1.0,1.0) + t*Color::new(0.5,0.7,1.0);
+}
 
 fn main() {
-    let image_width = 256;
-    let image_height = 256;
 
-    println!("P3\n{image_width} {image_height}\n255\n");
+    // File
+    let mut default_file = "image.ppm";
 
-    for i in (0..image_height).rev() {
-        eprint!("\rScanlines remaining: {i:5}");
-        for j in 0..image_width {
-            let r = j as f32 / (image_width - 1) as f32;
-            let g = i as f32 / (image_height - 1) as f32;
-            let b = 0.25;
+    // Image
+    let aspect_ratio = 16.0 / 9.0;
+    let image_width = 800;
+    let image_height = (image_width as f64 / aspect_ratio) as u64;
 
-            let ir = (255.999 * r) as u32;
-            let ig = (255.999 * g) as u32;
-            let ib = (255.999 * b) as u32;
+    // Camera
+    let viewport_height = 2.0;
+    let viewport_width = aspect_ratio * viewport_height;
+    let focal_length = 1.0;
 
-            println!("{ir} {ig} {ib}");
+    let origin = Point3::new(0.0,0.0,0.0);
+    let horizontal = Vec3::new(viewport_width, 0.0, 0.0);
+    let vertical = Vec3::new(0.0, viewport_height, 0.0);
+    let lower_left_corner = origin - horizontal/2.0 - vertical/2.0 - Vec3::new(0.0, 0.0, focal_length);
+    
+    // Render
+    let args: Vec<String> = env::args().collect();
+    if args.len() > 1 && args[1] != "" {
+        default_file = &args[1];
+    }
+    let mut file = BufWriter::new(File::create(default_file).unwrap());
+    writeln!(&mut file,"P3\n{image_width} {image_height}\n255\n").unwrap();
+
+    for j in (0..image_height).rev() {
+        eprint!("\rScanlines remaining: {j:5}");
+        for i in 0..image_width {
+            let u = i as f64 / (image_width-1) as f64;
+            let v = j as f64 / (image_height-1) as f64;
+            let r = Ray::new(origin, lower_left_corner + u*horizontal + v*vertical - origin);
+            let pixel_color = ray_color(&r);
+
+            color::write_color(&mut file, pixel_color);
         }
     }
     eprintln!("\nDone!");
-
-    let v = Vec3::new(1.0,2.0,3.0);
-    println!("{:?}",v)
 }

src/ray.rs

@@ -0,0 +1,25 @@
+use super::Point3;
+use super::Vec3;
+
+pub struct Ray {
+    pub orig: Point3,
+    pub dir: Vec3
+}
+
+impl Ray {
+    pub fn new(o: Point3, d: Vec3) -> Ray {
+        Ray { orig: o, dir: d }
+    }
+
+    pub fn origin(&self) -> Point3 {
+        self.orig
+    }
+
+    pub fn direction(&self) -> Vec3 {
+        self.dir
+    }
+
+    pub fn at(&self, t: f64) -> Point3 {
+        self.orig + t*self.dir
+    }
+}

src/vec3.rs

@@ -1,16 +1,14 @@
 use std::ops::*;
-use std::io::Write;
 
 #[derive(Clone, Copy, Debug)]
 pub struct Vec3 {
     pub e: [f64; 3],
 }
 
-type Color = Vec3;
-type Point3 = Vec3;
+pub type Color = Vec3;
+pub type Point3 = Vec3;
 
 impl Vec3 {
-
     pub fn new(x: f64, y: f64, z: f64) -> Self {
         Vec3 { e: [x, y, z] }
     }
@@ -107,7 +105,3 @@ impl Div<f64> for Vec3 {
         Vec3::new(self.x()/rhs, self.y()/rhs, self.z()/rhs)
     }
 }
-
-fn write_color(out: &mut impl Write, pixel_color: Color) {
-    write!(out, "{} {} {}\n", 255.999*pixel_color.x(), 255.999*pixel_color.y(), 255.999*pixel_color.z());
-}