fx: sphere hit calculation sometimes picking wrong isct point

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(