thanks for the help, Duncan. but when you said "study some geometry", do you mean the rgl package pdf reference mannual or other documents? please clarify. i am a total beginner on rgl. graham -- View this message in context: http://r.789695.n4.nabble.com/RGL-Drawing-Circle-tp4278717p4288776.html Sent from the R help mailing list archive at Nabble.com.