Yes, that is my problem. I could never reproduce in computer the scheme I learned in Computer Engineering graduation I am coursing. The way the teachers show and in some books, I never get into that result but I don't know if it is exactly impossible. At this page in wikipedia: http://en.wikipedia.org/wiki/Three-dimensional_space shows at the first image the exact position of the axes that until today I coudn't reproduce. I must have spent more than 10 hours hardly trying to archieve this with no luck. I would really love and thank full response on this question. Thank in advance!