This is true for computational science applications. A voxel in an MRI-scan is indeed not a little cube, but a data-point. Same for sampling 2D images (e.g. pho

This is true for computational science applications. A voxel in an MRI-scan is indeed not a little cube, but a data-point. Same for sampling 2D images (e.g. photography). In modern pixel/voxel art, however, the whole point is that they are in fact little squares and cubes. Otherwise you don't get the aesthetic this style is aiming for. It should be noted for historical accuracy, that the origins of pixel art were displayed on relatively blurry CRT screens, and your pixels didn't actually look like little squares either, more like glowy blobs. That's a different point than the cited paper is making, however, which is about the sampling theorem where pixels and voxels are basically data points (that can be interpolated in various ways). On the other hand, when I played 16 colour 320x200 games like Commander Keen and Duke Nukem (2D) in the 90s on a VGA CRT monitor, the pixels definitely looked like little squares, not blobs. Edit: maybe I should mention the oldschool ANSI art as well (BBS/demoscene), which were made with various coloured ASCII-blocks, and there the "pixels" were in fact quite obviously little blocks (and sometimes other characters but that's more ASCII-art than ANSI).