Abstract: A flight simulator combines flight data and polygon face terrain data to provide a CRT display for the windows of an aircraft trainer. The data base contains position data defining the relative position of each vertex of each polygon face, and visual data concerning the color, intensity, etc. of each face. In addition, the data base contains resolvability data for determining which faces, as displayed on the CRT, would have dimensions less than the resolvability of the display system. The resolvability standard is defined by a resolvability code (RC) and is based on the smallest resolvable angular subtense (.theta.rc). The angular subtenses (.theta. major and .theta. minor) of each face is determined by representing each face by a rectangle having a long side (S major) and a short side (S minor), and combining these side values with o (the S major unit vector) and n (the unit vector normal to the plane of S major and S minor) in a trigonometric relationship. .theta. major is compared with .theta.