okey. you see...
i ll try in poly... i was so angry after 2-3hours...... try & try & try...

i ve tried it on a simply object too. i thought i understand how it works
Actually on the first picture the black part >>> its trimmed out part. you can see on the right edge where the circle part re.
The program trimmed ouit very-very imprecisely

btw

thanks for your comment