I implemented a variation on marching cubes for this demo [0] based partially on readings from this author. It mainly handles smoothing of corners so I can still apply textures adequately, not a perfect by-the-book implementation. Very performant in the browser across thousands of vertices. Was very grateful for this work!

(Note: I'm a SaaS company founder, not a game developer, so forgive the rough edges.)

Edit: If you notice lagging, it's actually synchronous Voxel / terrain generation, not the rendering! Never did offload it to a separate thread like I had planned. Built this during the start of the pandemic in a weekend or two.

[0] https://play.sunfall.co/