latest changes

src/sphere.rs

@@ -0,0 +1,42 @@
+use crate::hittable::*;
+use crate::vec3::*;
+
+struct Sphere {
+    center: Point3,
+    radius: f64
+}
+
+impl Sphere {
+    pub fn new(center: Point3, radius: f64) -> Self {
+        Sphere {center, radius}
+    }
+}
+
+impl Hittable for Sphere {
+    fn hit(&self, r: &crate::ray::Ray, t_min: f64, t_max: f64, rec: &mut HitRecord) -> bool {
+        let oc = r.origin() - self.center;
+        let a = r.direction().length_squared();
+        let half_b = oc.dot(&r.direction());
+        let c = oc.length_squared() - self.radius*self.radius;
+
+        let discriminant = half_b*half_b - a*c;
+        if discriminant < 0.0 { return false; }
+        let sqrtd = discriminant.sqrt();
+
+        // Find the nearest root that lies in the acceptable range
+        let mut root = (-half_b - sqrtd) / a;
+        if root < t_min || t_max < root {
+            root = (-half_b + sqrtd) / a;
+            if root < t_min || t_max < root {
+                return false;
+            }
+        }
+
+        rec.t = root;
+        rec.p = r.at(rec.t);
+        let outward_normal = (rec.p - self.center) / self.radius;
+        rec.set_face_normal(r, &outward_normal);
+
+        return true;
+    }
+}