fx: sphere hit calculation sometimes picking wrong isct point

src/objects/materials/dielectric.rs

@@ -24,7 +24,7 @@ impl Material for Dielectric {
             self.refraction_index
         };
         let unit = ray.dir().get_unit();
-        let refr = unit.refract(hit.n(), ri);
+        let refr = unit.refract(&hit.n().get_unit(), ri);
         Some((Ray::new(*hit.p(), refr), Colour::new(1., 1., 1.)))
     }
 }

src/objects/sphere.rs

@@ -42,7 +42,9 @@ impl Hittable for Sphere {
         if d < 0. {
             None
         } else {
-            let t = (h - sqrt(d)) / a;
+            let tl = (h - sqrt(d)) / a;
+            let tr = (h + sqrt(d)) / a;
+            let t = if tl > 0.001 { tl } else { tr };
             let p = r.at(t);
             let out_n = (p - self.center) / self.radius;
             Some(Hit::new(