1. Tiling halves triangle count. When texture atlas is one dimensional (1x256 instead of 16x16, http://i53.tinypic.com/34tbdeh.jpg
), textures can be tiled in one direction.
This was an early test. Three top faces can be tiled into one. (Front faces too)
Side effect: game sees multiple rail blocks and tries to tile, so this ramp is created. This bug is nice because such ramps were planned. (however bug only works in one direction).
2. In previous versions fog wasted a lot of view range. Blocks hidden in fog were rendered anyway.
Current view range 32 is the comparable to previous 64. Even fog range 16 works, with 3k-6k triangles used - a software renderer could handle that.
I don't remember why, but fog color had to be changed to blue (to sky color).
Compare triangles used: (in reality the improvement is just 3x-5x because OpenGL display lists perform their own view frustum culling anyway, at least on Geforce 7600GT)
3. CPU usage is 5x-10x lower. This was done by replacing OpenGL immediate mode calls with vertex arrays, caching, replacing Lists with arrays, and using some better algorithms.