Lut-based system for simulating sensor-assisted perception of terrain

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. A reflectance LUT is provided for simulating the act of reflecting filtered radiation (light) off the material surface of the given terrain texel to thereby obtain a reading of the amount of light that the surface of the texel will reflect. The reflectance and sky contribution factors are multiplied to obtain a per-texel signal representing the amount sensor-detectable light produced from each terrain texel. A generally similar approach is taken to determine what amount of sensor-detectable, black body radiation will be produced from each terrain texel. Each terrain texel is simulated as having a specifiable mixture of plural surface materials. Each terrain texel is allowed to be shadowed during different times and the per-texel shadowing is accounted for.