The difference between digital and analog vanishes if the resolution is equivalent. In the real and practical world, any image source can be converted to digital information with less loss than would occur in the distortion components of analog processing.
You keep repeating the claim that VP-8 doesn’t alter the data, but you haven’t given this claim any actual thought.
Displayed images are inherently two dimensional. There is no z-axis. When you produce a 3D effect on a two dimensional display you are altering the data.
The only way the human eye can interpret a two dimensional display as three dimensional image is if there are light and dark areas consistent with light and shadow The apparent light source has to come from some direction or another. There are lots of optical illusions based on this phenomenon, including images of mood craters that appear to be hills if the image is turned upside down.
The z-axis in the VP-8 image is an interpretation.
I have given it a lot of thought. Informed thought.
I have claimed that the VP-8 presents the data in a form where the reflected light intensity for each area scanned is plotted, converted if you will, proportionately to the Z axis on a three-dimensional grid where X and Y axes plot the location of that particular scan point. The VP-8 then adds a virtual light source and allows the three-dimensional grid to be rotated and viewed from an position. The DATA are not altered, merely transformed into a more convenient form to visualize. It makes a representation of the data in a two-dimensional plane which can be manipulated to see it better. As I stated you could also plot the data onto a two-dimensional grid in the form of numbers to represent the varying intensities of the reflected light from the image.
One could, and some researchers have, taken the data and plotted it in a REAL three-dimensional grid, taking the data converted from intensity to relative distance from zero on the Z axis, and carving those distances into a block of styrofoam. All the data manipulation is conversion from grey scale intensity percentage to distance from an arbitrary, fxed starting plane on the X, Y axes plane. It is a purely linear function.
I refer you again to the statement of the inventor and designer of the VP-8 Image Analyser:
The VP-8 Image Analyzer can vary the elevation scale (Z axis) relative to the X and Y axis scale. The VP-8 cannot change the linearity of the Z axis response, unless the unit is un-calibrated or the camera is improperly operated. A change of 10 percent in the incoming light level will produce an elevation change of 10 percent on the Z axis. It is a direct, linear function.
I would interpret from that, that a 10 unit change in image intensity from the base background image intensity is plotted as a 10 unit increase in the distance from zero on the Z-axis. That is the algorithm you are seeking.