//¤@­Ócheck½d¨Ò
//==========================================================
//      ground plane
surface {                                
        texture {                        
                pattern checker          
                scale 5 5 0              
                surface { diff blue }    
                surface { diff red }     
        }                                
}                                        
ring {                                   
        center 0 0 -2                    
        normal 0 0 1                     
        radius 100                       
     }
//==========================================================