DPI is Dots Per Inch and refers to the number of dots that a printer makes per inch. It has nothing to do with pixels.

PPI is Pixels Per Inch and has something to do with how big an image will be when you print it.

You can print a 300 PPI image on a 2400 DPI printer - all that means is that a pixel will be printed as 64 (8x8) dots.

Some scanners have a dialog box asking you for what DPI you want to scan at - this is incorrect terminology. The scanner should be asking you for PPI. DPI has nothing to do with PPI.

And rendering parameters have nothing to do with PPI either. You render to a certain number of pixels - period. How you print them (later) is not involved in the calculation.

And a shading rate of 1 does not mean that the texture map associated with the geometry will be rendered at 1 texture pixel = 1 screen pixel, nor does it mean that a micro-polygon is exactly covering one pixel in the render. With displacement, a micro-polygon can be sheared to cover many pixels. Furthermore, I can scale an entire 4K by 4K image map to fit in one pixel in the render. Simply make a one-sided square cover only one pixel, and attach an image. The entire square will be rendered into one pixel. Now, how many pixels of the attached image will be consulted? Do you think all 16 million are consulted to produce an average color for the whole image? Nope. Only 4 samples will be taken - one at each corner of the square, because the square is so small the area is already the size of a micropolygon and so will not be further sub-divided.

As for the 4000 number versus 4096, that's just what some sloppy people do. There are plenty of texture makers who produce 4K (4096) dimensions. And some who actually mean 4K say 4000 by mistake, but actually have produced a 4096 dimension image.

And ... as for whether using 4000 is stupid and bad practice, it just means you could have had 96 more pixels of detail, but you don't. The renderer still expands the image to a power of 2 before doing mip-mapping.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)