Abstract: A set of specially-configured LUT's are used in a rasterizing portion of a graphics system for simulating Sensor-assisted Perception of Terrain (SaPOT) so that simulation of the image produced by a given sensor can proceed rapidly and with good accuracy at a per-texel level of resolution. More specifically, terrain texels-defining memory is provided with a plurality of addressable texel records where each record contains: (a) one or more material identification fields (MID's); (b) one or more mixture fields (MIX's) for defining mixture proportions for the materials; and (c) slope-defining data for defining a surface slope or normal of the corresponding texel. A sky-map LUT is provided for simulating the act of looking up to the sky along the normal surface vector of a given texel to thereby obtain a reading of the sky's contribution of illumination to that terrain texel.