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public void LoadFromXML(XmlTextReader reader)
        {
            cameras.Clear();
            lights.Clear();
            objects.Clear();

            reader.ReadStartElement("Scene");

            reader.ReadStartElement("Cameras");

            while(reader.IsStartElement("Camera"))
            {
                RTCamera camera = new RTCamera();
                camera.ReadFromXML(reader);
                cameras.Add(camera);
            }

            reader.ReadEndElement(); //Cameras

            reader.ReadStartElement("Lights");

            while (reader.IsStartElement("Light"))
            {
                reader.ReadStartElement("Light");
                RTLight light = null;

                if (reader.IsStartElement("PointLight"))
                    light = new RTPointLight();

                light.ReadFromXML(reader);
                lights.Add(light);
                reader.ReadEndElement(); //Light
            }

            reader.ReadEndElement(); //Lights

            reader.ReadStartElement("Objects");

            while(reader.IsStartElement("Object"))
            {
                reader.ReadStartElement("Object");
                //Parse each type of object here.
                reader.ReadEndElement(); //Object
            }

            reader.ReadEndElement(); //Objects

            reader.ReadEndElement(); //Scene
        }