You could look at it this way:
xDNA is a method for summarizing multiangle spectral data into a two- or three-dimensional spectral representation. The xDNA is a weighted vector sum of the measurement directions, with the weights being the reflectance factors for each direction. The result of this sum is a spectrum of points in 2D or 3D space, one point for each measured wavelength.
The weighted vector sum is also scaled by the length of the vector sum of an ideal white Lambertian reflector in order to make the xDNA values reasonably comparable to typical reflectance values. The coordinate system for xDNA consists of the specular direction (z axis), the projection of the illumination direction orthogonal to specular (y axis), and the cross product of these two directions (x axis) . . .
That's from an "introduction" to xDNA technology from X-Rite (www.xrite.com; Grand Rapids, MI). There are twelve more pages. Which, if nothing else, seems to indicate the scientists, technicians, and engineers behind this development know what they're doing.
Or, here's another way of understanding the xDNA system and its associated handheld spectrophotometer:
If you want to apply metallic flake, pearlescent, and other effect paints in a consistent way based on measurement and analysis and that saves time, money and resources, this is the technology for you.
Apparently the problem is accurately measuring the color and appearance of paints that "sparkle." The sparkling throws off optical instruments. What this means is that the surfaces of parts including body panels and fascias that are painted with the "same" paint can look different under different illuminations and from different angles. Consequently, if the parts are assembled, then it might appear as though there are two different paints in play. Certainly not the sort of thing that a customer opting for a premium paint job would be pleased with. So the approach has been to do a whole lot of trial-and-error work. Time-consuming work. Apparently, one vehicle manufacturer's paint personnel had spent more than two months working on the fascia-body panel mismatch issue, trying to determine the root cause via measuring the results with consistency and accuracy. Using the xDNA system, the measurements and the match were made in three days.
"We coined the term 'xDNA' to emphasize the fact that each effect paint has a unique, three-dimensional mathematic model, similar to the way that each person has a unique DNA structure," said Brian Teunis, market manager, X-Rite's industrial color and appearance division. Which would bring us back to the opening paragraphs, mathematically speaking. But more to the point, what the system offers is a means by which users can determine whether the mismatch is due to the application equipment or the paint formulation; whether existing equipment can be adjusted sufficiently to handle a new process; determine whether a process is going out of control; and predict whether there is a perceptible change if the paint formula or process parameters are changed.
The MA98 is a hand-held (it weighs about two pounds and is designed to be held by both hands) battery-powered instrument that provides 10 measurement and two illumination angles to create a master profile of each color surface. The measurements, which are made in approximately two seconds, are then processed with the X-ColorQC software package which uses proprietary xDNA algorithms. The output are graphs that show the characteristics of the effect paint under assessment.