In this paper, we describe a method of 3D modeling based on photographs for real-time graphics system of educational use. The method uses few basic models like squares, spheres and so on, and a 3D model is constructed by modifying basic models, guided by parameters. For example, we made an educational real-time graphics system of the deep space, having galaxies' 3D models. A typical galaxy called spiral galaxy consists of two parts; a spherical center part named bulge, and a whirlpool convex-lens shaped surrounding part named galactic disc. Galaxies' photographs are taken from a limited angle, because they are too far away, and viewed only from the earth. So a galaxies' photograph is whether in a whirlpool form, a convex-lens form, or in a slant form between the two forms. Therefore our method puts a sphere model at the bulge position, and a convex-lens model formed by a sphere metamorphism at the galactic disc position. Parameters are used to change galaxies' position, size, XYZ-axes metamorphism and rotation. Thus we get a 3D galaxy model corresponding to the photograph, and learners can look at a 3D galaxy from any viewpoint and view direction. In this way, we construct realistic 3D models. The amount of rendering computation is still low. Thus real-time rendering images are produced freely from a moving viewpoint and view direction.