I set up a Minecraft server for some friends a few weeks ago, and I learned firsthand how huge of a performance improvement one can get by dropping the render distance.
My basic understanding of the problem is that it's less of a graphics problem and more of a CPU one. Loading another chunk requires the game to actively simulate everything happening in that chunk, and, since the game is single-threaded, increasing the number of chunks loaded quickly causes the amount of work needing to be done per tick to explode.
I know nothing about the codebase and haven’t done any projects related to game engines/physics rendering, but I’ve seen a lot of games that seem to have “high level” and “low level” simulations. I’ve walked too far too quickly on older systems in open world games and have often noticed lower resolution models that are designed to be seen from far away.
Am I right in thinking that Minecraft doesn’t do that? And that everything rendered uses the same resolution models for things far away as for things close up?
What you are thinking of is called Level of Detail (LOD). The principle being that 3D models further away can be rendered with fewer vertices/polygons, i.e., at a lower LOD. 3D models in Minecraft are almost all simple cubes or a collection of rectangles (e.g., torches, levers, slabs). There aren't really any extra polygons in these models that can be removed to create a less detailed representation, unlike, say in this [1] model of a rabbit.
Thus, you are right in thinking that Minecraft doesn't implement a LOD by changing the resolution of the models; however, it does use progressively lower resolution textures for texturing models that are farther away. This is a common technique called mipmapping [2].
My basic understanding of the problem is that it's less of a graphics problem and more of a CPU one. Loading another chunk requires the game to actively simulate everything happening in that chunk, and, since the game is single-threaded, increasing the number of chunks loaded quickly causes the amount of work needing to be done per tick to explode.