For something like Minecraft where the voxels are comparatively huge they’re probably using something like Marching Cubes to extract a poly mesh from the voxel

For something like Minecraft where the voxels are comparatively huge they’re probably using something like Marching Cubes to extract a poly mesh from the voxel chunks rather than ray tracing. You can actually get pretty far with surface extraction techniques see for example the VoxelFarm engine.