BRL is a lightweight rendering libary, used so modders can add things in, with ease and without lag. BRL can do things on its own too.

BRL on its own is nowhere near as utilized as with other mods, however there are still some cool things you can do.

Use .tbl files to render with, instead of the traditional .json files. (Put the .tbl file in the same directory as the block model you want to override, but keep the .tbl file extension).
Remove detail of block textures. What this does, is remove the block details, making each texture just the avarage color of all the block. This creates a nice, smooth effect (see below). This will also work for modded blocks, and non-default texture packs. It's like a texturepack for a texturepack! (Use command '/brl plastic' to toggle)

With mods, BRL can really be utilized.

Similar to ISimpleBlockRenderingHandler, BRL can render blocks, that are location based. This means that the block can change its apperence based on what is around it, or where it is. You can already do this with TESR, however they can be very laggy/buggy if lots are used at once. This can also be used to render more that one block model for a block, and also be used to render textures that aren't registered to the texturemap.
Replace a block state, only for rendering. This means that you can make a blockstate render as a certian block, and have that block have all the same functions as before.

BetterRenderLib