Implementing a Lighting Engine for Voxelworld

A single torch at night.

A cave with a blue and green torch.

Some lava.

An entrance to a creepy dark cave.

My main focus for v0.3.0 for Voxelworld has been to implement a very basic lighting engine. The lighting engine is not going to be that fancy - there’s not going to be things like ambient occlusion or smooth lighting so in that aspect it is inferior to Minecraft’s lighting engine. I might implement those features in the future when I have time and motivation. But for now, I just implemented something similar to what Minecraft lighting was like in the Alpha edition.

One bonus that this lighting engine has over Minecraft’s lighting engine is that it supports colored lighting (so you could have things like red, green, and blue torches). I made the lava emit orange light and I really like how it looks in the caves.

Light is not stored in the world save, it’s just generated on the fly when you load into a world or when you generate new chunks. The performance is passable on my laptop (at least most of the time, sometimes there are noticeable lag spikes) for a render distance of 7 chunks. It’s definitely worse than other voxel games like Minecraft and Minetest (I think it’s called Luanti now but I’m still calling it Minetest) but I think it’ll be fine for now. Adding colored lighting was actually not that difficult, all I had to do was store each channel seperately and propagate each channel’s light values individually. Light propagation is actually surprisingly similar to the water physics except for the fact that light is not affected by gravity. Essentially it’s just a BFS from a light source to the rest of the world.

Sky light was a little more difficult to implement, Voxelworld uses cubic chunks which means that some chunks above the player are not loaded and those unloaded chunks might contain blocks that would affect sky light levels in the loaded chunks. I considered many ways of dealing with this but ultimately I decided that almost all of the time anyone using this program would likely not end up running into this issue since most of the chunks above should be completely empty. I just chose the simple but technically not 100% correct option of just generating sky light on the fly when the world is loaded and when new chunks are generated/loaded. This could lead to some potentially strange results in some extreme edge cases but I feel that those are manageable and it works fine enough for now.

Another thing of note about sky light is that sky light does not attenuate downwards when it has a level of 15 but the moment it becomes <= 14, it starts to attenuate in all directions. I believe that this technically is not how Minecraft does it but I’ve decided to keep it in as it looks fine enough.

Also, another thing to note about the lighting engine is that there might be room for optimizations, particularly those relating to generating new light in newly loaded chunks (especially with sky light). However, I think for now it performs well enough and I’m debating releasing v0.3.0 sometime in the near future. The next goal would be to figure out some more optimizations in things like chunk rendering (so as to increase the render distance) and also begin implementing things like survival mode.

If you would like to try out the game or test out the lighting engine, go to Voxelworld’s itch.io page and consider giving it a shot!

Anyway, that’s it, have a nice day.

By the way, I implemented dynamic lighting - if you’re holding an item that emits light it will light up the surroundings. It does not affect the light levels of the blocks but it’s a nice visual effect. The screenshot shows this with the player holding a torch.