2 files changed, 44 insertions(+), 4 deletions(-)

M src/main.rs
A src/ray.rs

@@ 4,7 4,19 @@ use vec3::*;
 mod ray;
 use ray::*;
 
+fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> bool {
+    let oc = r.origin() - *center;
+    let a = dot(&r.direction(), &r.direction());
+    let b = 2.0 * dot(&oc, &r.direction());
+    let c = dot(&oc, &oc) - radius*radius;
+    let discriminant = b*b - 4f64*a*c;
+    discriminant > 0.0
+}
+
 fn ray_color(r: &Ray) -> Color {
+    if hit_sphere(&Point3::new(0.0, 0.0, -1f64), 0.5, r) {
+        return Color::new(1.0, 0.0, 0.0);
+    }
     let unit_direction = unit_vector(r.direction());
     let t = 0.5 * (unit_direction.y() + 1.0);
     (1.0 - t) * Color::new(1.0, 1.0, 1.0) + t * Color::new(0.5, 0.7, 1.0)


@@ 17,6 29,7 @@ fn main() {
     // Image
     let aspect_ratio = 16.0 / 9.0;
     let image_width = 400;
+    let image_width = 800;
     let image_height = (image_width as f64 / aspect_ratio) as i32;
 
     // Camera


@@ 25,11 38,11 @@ fn main() {
     let viewport_width = aspect_ratio * viewport_height;
     let focal_length = 1.0;
 
-    let origin = Point3::new(0f64, 0f64, 0f64);
-    let horizontal = Vec3::new(viewport_width, 0f64, 0f64);
-    let vertical = Vec3::new(0f64, viewport_height, 0f64);
+    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 / 2f64 - vertical / 2f64 - Vec3::new(0f64, 0f64, focal_length);
+        origin - horizontal / 2f64 - vertical / 2f64 - Vec3::new(0.0, 0.0, focal_length);
 
     // Render
 

@@ 0,0 1,27 @@
+use crate::vec3::*;
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct Ray {
+    orig: Point3,
+    dir: Vec3,
+}
+
+impl Ray {
+    pub fn new(orig: &Point3, dir: &Vec3) -> Self {
+        Ray {
+            orig: *orig,
+            dir: *dir,
+        }
+    }
+
+    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
+    }
+}