Model-based pose estimation techniques which match image and model triangles require large numbers of matching operations in real world applications. We show that by using approximations to perspective, 2D lookup tables can be built for each of the triangles of the models. An approximation called \weak perspective" has been applied previously to this problem; we consider two other perspective approximations, paraperspective and orthoperspective. These approximations produce lower errors for oo-center image features than weak perspective. The errors of these approximations are evaluated by comparison with exact solutions. The error estimates show the relative combinations of image and triangle characteristics which are likely to generate the largest errors. The corresponding cells of the lookup tables can be agged, so that object pose calculations would disregard image and model triangle pair combinations when their characteristics correspond to the agged cells.