Principal axes and scales of an arbitrarily given axonometric drawing based on Pohlke's theorem are clearly shown with an ellipse projected by a sphere in the same condition. To obtain the ellipse, we develop a new method by applying the concept of an ellipse of inertia of a section.

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Approximating the surface spanning a given set of 3D points as a polyhedron of triangular faces (triangulation) is one of the significant problems, and has many applications in the fields of computer graphics and computer vision. In this paper, several solutions to this problem are reviewed. These solutions have the problem that contour lines of irregular surfaces, such as found in nature, do not lend themselves to curve fitting. We developed an efficient and precise heuristic method for triangulation of the 3D surface formed by spanning a set of planar contours. The most efficient triangulation is presented newly in the paper by judging from the similarity in the shapes of adjacent contours.And this method can generate without depending on the shapes of contour lines. The program was designed to interface contour definitions of the components of a human head.

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