I've been working on a voxel engine in my spare time for 10 years, this year. I wrote everything from scratch, from the memory allocators, font rasterizer and a programing language all the way to collision detection, renderer and gameplay code. It's been a journey!
After seeing your renders on github, a question I always have is why voxels are stereotypically 1m square... wouldn't the ideal voxel engine immediately set the scale to something more high-res? I'm just drooling at the thought of a voxel engine where a block size is equivalent to the size of a physical pixel.
https://github.com/scallyw4g/bonsai
https://github.com/scallyw4g/poof