1 files changed, 10 insertions(+), 4 deletions(-)

M src/main.rs

@@ 4,18 4,24 @@ use vec3::*;
 mod ray;
 use ray::*;
 
-fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> bool {
+fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> f64 {
     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
+    if discriminant < 0.0 {
+        -1.0
+    } else {
+        (-b - discriminant.sqrt() ) / (2.0*a)
+    }
 }
 
 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 t = hit_sphere(&Point3::new(0.0, 0.0, -1f64), 0.5, r);
+    if t > 0.0 {
+        let N = 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 = unit_vector(r.direction());
     let t = 0.5 * (unit_direction.y() + 1.0);