I'm sorry that i can't understand the concept of collision avoidence i don't know why? please send me an algorithm helping me in solving this problem. i read so much about this problem but there no preecding. thanks for help _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".