Computer graphics appeared only thirty years ago. Today, there-dimensional (3D) computer graphics are widely employed by movies, computer games and many other industries. Thanks to this new technology, the computer-generated images on the screen are realistic and believable. However, there are other ways to create 3D illusions. They are drawing and painting. The traditional 3D illusion masters like Leonardo DaVinci used brush and paint to simulate the concept of 3D space. So, computer 3D graphic and traditional fine art must have some mutual principles in order to reproduce the 3D illusions. In this thesis, the author discusses the connections and similarities between these two techniques, as well as differences. The discussion is divided into proportion, value, anatomy, and perspective for aspects. A digital reproduction of an angel's head of Leonardo's "Madonna of the rock" was presented as an example to demonstrate these relationships. The author argues that the basic art training such as drawing is equally important to both computer 3D artists and painters. The main purpose of the thesis is to clarify these connections and relationships, and to give 3D computer artists specific guidelines and clues to improve their ability to produce more realistic images, and even to meet the traditional realistic art standard.