simplify Sphere#hit

src/main/java/eu/jonahbauer/raytracing/shape/Sphere.java

@@ -24,16 +24,16 @@ public record Sphere(@NotNull Vec3 center, double radius) implements Shape {
         var oc = ray.origin().minus(center());
 
         var a = ray.direction().squared();
-        var b = 2 * ray.direction().times(oc);
+        var h = ray.direction().times(oc);
         var c = oc.squared() - radius * radius;
 
-        var discriminant = b * b - 4 * a * c;
+        var discriminant = h * h - a * c;
         if (discriminant < 0) return Optional.empty();
 
         var sd = Math.sqrt(discriminant);
 
-        double t = (- b - sd) / (2 * a);
-        if (t < 0) t = (-b + sd) / (2 * a);
+        double t = (- h - sd) / a;
+        if (t < 0) t = (- h + sd) / a;
         if (t < 0) return Optional.empty();
         return Optional.of(new HitResult(t, ray.at(t).minus(center)));
     }