diff --git a/src/basics.cc b/src/basics.cc
index 63ffd5c..8dd91d4 100644
--- a/src/basics.cc
+++ b/src/basics.cc
@@ -205,6 +205,19 @@ Vector3::dot(const Vector3 &v)
 }
 
 
+/*
+ * Vector3::cross --
+ *
+ * Compute and return the cross product of this and the given vectors.
+ */
+Vector3
+Vector3::cross(const Vector3 &v)
+    const
+{
+    return Vector3(y*v.z - z*v.y, z*v.x - x*v.z, x*v.y - y*v.x);
+}
+
+
 /*
  * Vector3::normalize --
  *
diff --git a/src/basics.h b/src/basics.h
index 2ec9a27..ab6b16a 100644
--- a/src/basics.h
+++ b/src/basics.h
@@ -34,6 +34,7 @@ struct Vector3
     float length2() const;
     float length() const;
     float dot(const Vector3 &v) const;
+    Vector3 cross(const Vector3 &v) const;
 
     Vector3 &normalize();