Kavita Bala asked, “What is the etymology of ‘tap’ in texture filtering?”<\/p>\n
This is a term we use in graphics for taking a sample from a texture map. I didn’t know where it came from, and recall being\u00a0a bit mystified as to what it even meant when I first encountered it, finally puzzling it out from the context. Searching\u00a0around now, the earliest reference I could find in 3D graphics literature was in this article<\/a>, so I asked Dave Luebke,\u00a0who coauthored that paper.<\/p>\n Dave replied:<\/p>\n I think it’s actually very old and references the idea of putting a probe, as in an oscilloscope, to tap a signal (like tapping a pipe, meaning to take water out of it at a particular location, or tapping a maple tree for sap to make syrup from).<\/p>\n Dave asked two other experts.<\/p>\n Lance Williams replied:<\/p>\n It’s traditional filter terminology. For example:<\/p>\n “Filter Coefficients – the set of constants, also called tap weights, used to multiply against delayed signal sample values within a digital filter structure.”<\/p>\n “A direct form discrete-time FIR filter of order N. The top part is an N-stage delay line with N + 1 taps.”<\/p>\n “For FIR filters, there is no denominator in the transfer function and the filter order is merely the number of taps used in the filter structure.”<\/p>\n John Montrym replied:<\/p>\n Follow this trail:<\/p>\n