title: How to use ScnNode as a ScnLight?
body: <pre><code> var sun = SCNNode(geometry: SCNSphere(radius:0.35))
  
   sun.geometry?.firstMaterial?.diffuse.contents=#imageLiteral(resourceName: "Sun")
  
   sun.position=SCNVector3(0,0,-1)
  </code></pre>
  
  <p>And i want to use the sun SCNSphere as a omni light source.</p>
  
  <pre><code> let OmniLight = SCNLight()      
    OmniLight.type = SCNLight.LightType.omni
         OmniLight.color = UIColor.white
  </code></pre>
  
  <p>But if i run this code, the sun is full black.</p>