Notch has made a couple of comments on reddit :
http://www.reddit.com/r/programming/comments/146v69/how_notc...
Please do NOT write code like this. It was originally written for the Java4k
competition, which focuses on executable code size, and is as a result almost
intentionally poorly written. It got even worse when I ported it to JS.
It was mainly meant as a test for me to see what HTML5/JS can do, and an
exercise in porting code over.
It would run a bit smoother if it was written in C++ (mainly due to not having
to rely on the GC, and having it precompiled gets rid of the warmup time), and
modern OpenGL would help quite a lot as well. A lot of the stuff done in CPU
now could be moved to a shader, which both makes code simpler, and gets rid of
the slow JNI calls required now.
The main reason why Minecraft is slow is mainly 1) There's a LOT of polygons,
combined with 2) The difficulty of making an efficient culling algorithm in a
dynamic world.
If someone solves #2, very interesting things could be made with a game similar
to Minecraft.
No, they don't get merged because the textures are all pulled from the same atlas
to avoid texture swapping. With GLSL, they could be merged, saving quite a lot of
polygons. For a while, I did attempt switching the atlas from a 16 x 16 grid to a
1 x 256 grid and merging horizontal runs of the same texture, but the resulting
texture size was to tall some graphics cards (on low end computers) would
automatically downsample it.
The problem with the occlusion culling is not about knowing what parts are static,
but rather figuring out what occluders there are. It would be very beneficial not
to have to render caves under ground below the player, for example, or not to
render the entire outside when a player is inside a small closed house. Figuring
this out in runtime on the fly as the player moves around is.. expensive.