Software occlusion culling in Block Game

My GPU is the integrated Radeon Vega 8 that comes with my AMD Ryzen 7 5700G CPU. I tell you this so you know that my workstation is not a graphical computing powerhouse. It is, in fact, quite weak. To its credit my integrated GPU shows up as 48% faster on UserBenchmark than the GPU in my low end hardware target; a laptop I bought in 2012.That, and the fact I want my game to run well even on a potato, is why I recently decided to try my hand at writing a software rendered occlusion culling solution for the Block Game (working title) I’m developing as I’ve always been interested in the idea. Blocks and chunks are axis aligned cubes, which makes things easier, and block games tend to have a ton of hidden geometry in the form of underground caves. There are other ways to cull these, but the algorithms tend to be fairly complex and this seemed like a good way to avoid that complexity and stick with something very conceptually simple.In this post I’ll be explaining the development process and the solution that I eventually landed on. If you like you can also read the development thread I posted on Mastodon and Bluesky.Before I start though I’d like to say that this came out quite well, better than I expected. It runs in half a frame at 60 FPS or less (threaded, of course) and generally culls at least 50% of the chunks that survive frustum culling. Above ground, looking straight ahead at the horizon it’ll cull around between 50 and 60% of chunks, but indoors and below ground in caves it can cull upwards of 95% of chunks, resulting in framerates of 400+ even on my weak system. All around a resounding success, though it has some cases where it breaks down which I’ll touch on at the very end of this post.Comparison of depth occlusion culling on/off, off on left, on on right.