1 files changed, 18 insertions, 2 deletions
diff --git a/ray.h b/ray.h
index 5a68557..db28d0f 100644
--- a/ray.h
+++ b/ray.h
@@ -10,11 +10,22 @@
 // A ray is a half-line, starts from a 3d point, along the direction of a unit vector, to the infinity
 template<typename T>
 class ray3 {
-    const vec3<T> source_;
-    const vec3<T> direction_; // unit vector
+    vec3<T> source_;
+    vec3<T> direction_; // unit vector
 
 public:
+    ~ray3() = default;
+
     ray3() = delete;
+
+    ray3(const ray3<T> &other) = default;
+
+    ray3<T> &operator=(const ray3<T> &other) {
+        source_ = other.source_;
+        direction_ = other.direction_;
+        return *this;
+    }
+
     ray3(const vec3<T> &source, const vec3<T> &direction) : source_(source), direction_(direction.unit_vec()) {}
 
     // Get the source point from where the ray emits.
@@ -32,6 +43,11 @@ public:
     vec3<T> at(U t) const {
         return source_ + direction_ * t;
     }
+
+    // Get a ray starts from zero and directs to undefined direction.
+    static ray3<T> null() {
+        return ray3<T>{vec3<T>::zero(), vec3<T>::zero()};
+    }
 };
 
 using ray3d = ray3<double>;