by more than some specified parameter e g as further described in conjunction with fig8 a sequence of zero or more propagate steps 262 extend the field out from the seeded positions the result is that force vectors pointing to pattern boundaries as well as other information needed by the run time steps can be obtained at some distance from the boundaries the number of propagate steps 262 is controlled by a parameter and determines the distance from pattern boundaries that the field will contain valid force vectors as well as the computation time needed for pattern training in a preferred embodiment four propagation steps are used field elements beyond the range of propagation will contain the code set during the initialization step 250 fig3 shows a preferred embodiment of a feature detector to be used for practice of the invention the feature detector processes a source image 300 which can be either a training image or a run time image a low pass filter 310 and image sub sampler 320 are used to attenuate fine detail in the source image that for a variety of reasons we wish to ignore for example we may wish to attenuate noise or fine texture or we may wish to expand the capture range of the pattern by focusing on coarse pattern features also we may wish to decrease the number of image dipoles thereby reducing processing time the response of the filter 310 and sub sampler 320 are controlled by parameters 220 stored in the pattern not shown in this figure one setting of the parameters effectively disables the filter and sub sampler allowing the source image 300 to pass without modification for maximum resolution methods for low pass filtering and.