add bounding box to sphere

src/main/java/eu/jonahbauer/raytracing/math/BoundingBox.java

@@ -0,0 +1,10 @@
+package eu.jonahbauer.raytracing.math;
+
+import org.jetbrains.annotations.NotNull;
+
+public record BoundingBox(@NotNull Vec3 min, @NotNull Vec3 max) {
+
+    public @NotNull Vec3 center() {
+        return Vec3.average(min, max, 2);
+    }
+}

src/main/java/eu/jonahbauer/raytracing/scene/Hittable.java

@@ -1,5 +1,6 @@
 package eu.jonahbauer.raytracing.scene;
 
+import eu.jonahbauer.raytracing.math.BoundingBox;
 import eu.jonahbauer.raytracing.math.Range;
 import eu.jonahbauer.raytracing.math.Ray;
 import org.jetbrains.annotations.NotNull;
@@ -14,4 +15,8 @@ public interface Hittable {
      * @param ray a ray
      */
     @NotNull Optional<HitResult> hit(@NotNull Ray ray, @NotNull Range range);
+
+    default @NotNull Optional<BoundingBox> getBoundingBox() {
+        return Optional.empty();
+    }
 }

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

@@ -1,6 +1,7 @@
 package eu.jonahbauer.raytracing.scene;
 
 import eu.jonahbauer.raytracing.material.Material;
+import eu.jonahbauer.raytracing.math.BoundingBox;
 import eu.jonahbauer.raytracing.math.Range;
 import eu.jonahbauer.raytracing.math.Ray;
 import eu.jonahbauer.raytracing.math.Vec3;
@@ -44,6 +45,14 @@ public record Sphere(@NotNull Vec3 center, double radius, @NotNull Material mate
         return Optional.of(new HitResult(t, position, frontFace ? normal : normal.times(-1), material, frontFace));
     }
 
+    @Override
+    public @NotNull Optional<BoundingBox> getBoundingBox() {
+        return Optional.of(new BoundingBox(
+                center.minus(radius, radius, radius),
+                center.plus(radius, radius, radius)
+        ));
+    }
+
     public @NotNull Sphere withCenter(@NotNull Vec3 center) {
         return new Sphere(center, radius, material);
     }