crux of minecraft floodfill lighting engine.glsl

voxel temp;

vox.sunlight = id.y == resolution.y - 1 ? 15 : 0;
vox.torchlight = 0.;

//pull 6 neighbours and -1
if (id.y < resolution.y - 1.) 
{
    temp = getVoxel(id + int3(0,1,0));
    vox.sunlight = max(vox.sunlight, temp.sunlight);
    vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);
}
if (id.y > 1.) 
{
    temp = getVoxel(id + int3(0,-1,0));
    vox.sunlight = max(vox.sunlight, temp.sunlight - 1.);
    vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);
}

temp = getVoxel(id + int3(-1,0,0));
vox.sunlight = max(vox.sunlight, temp.sunlight - 1.);
vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);
    
temp = getVoxel(id + int3(1,0,0));
vox.sunlight = max(vox.sunlight, temp.sunlight - 1.);
vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);

temp = getVoxel(id + int3(0,0,-1));
vox.sunlight = max(vox.sunlight, temp.sunlight - 1.);
vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);

temp = getVoxel(id + int3(0,0,1));
vox.sunlight = max(vox.sunlight, temp.sunlight - 1.);
vox.torchlight = max(vox.torchlight, temp.torchlight - 1.);

if (vox.id > 0.) 
{
    vox.sunlight = 0.;
    vox.torchlight = 0.;
}

if (vox.id == 6.) 
{
    vox.torchlight = 15.;   
}
fragColor = encodeVoxel(vox);