ft: 5,6.1: sphere class + normals

src/objects/sphere.rs

@@ -0,0 +1,44 @@
+use core::f32::math::sqrt;
+
+use crate::objects::hit::Hit;
+use crate::objects::traits::{Hittable, Normal};
+use crate::Vec3;
+
+pub struct Sphere {
+    center: Vec3,
+    radius: f32,
+}
+
+impl Sphere {
+    pub fn new(center: Vec3, radius: f32) -> Sphere {
+        Sphere {
+            center: center,
+            radius: radius,
+        }
+    }
+}
+
+impl Hittable for Sphere {
+    fn hit(&self, r: &crate::ray::Ray) -> Option<Hit> {
+        let oc = self.center - r.origin();
+        let a = r.dir().dot(r.dir());
+        let b = -2. * r.dir().dot(&oc);
+        let c = oc.dot(&oc) - self.radius * self.radius;
+
+        let d = b * b - 4. * a * c;
+
+        if d < 0. {
+            None
+        } else {
+            let t = (-b - sqrt(d)) / (2.0 * a);
+            let p = r.at(t);
+            Some(Hit::new(t, p, self.normal_at(&p)))
+        }
+    }
+}
+
+impl Normal for Sphere {
+    fn normal_at(&self, p: &Vec3) -> Vec3 {
+        (*p - self.center).get_unit()
+    }
+}