How far do I have to place torches so that mobs will not spawn near me?
Since torches prevent mobs from spawning, is it possible to place enough torches within a specific radius to ensure safety during the night? I'm thinking of a situation without any shelter built, more along the lines of a flat plain. If it is possible, how many torches/how far out do I need to go to make that area safe?
See also this related question (and answers): http://gaming.stackexchange.com/questions/15959/how-far-should-i-place-torches-in-a-planar-huge-room
Learn about light:
- Sunlight gives 15 luminance to the blocks it hits directly, or through half steps.
- Lava gives 15 luminance.
- Glowstone gives 15 luminance.
- A Jack-o-lantern gives 15 luminance.
- A Torch gives 14 luminance to the otherwise empty block it occupies.
- A Redstone torch gives 7 luminance to the otherwise empty block it occupies.
Every tile that isn't a light source has a luminance of one minus the luminance of its neighbors. For example, if you had a 6 and a 4 luminance sources close to each other, attached to a wall, you'd have this distribution:
1 121 1 12321 121 1234321 1232123454321 123432345654321 12┴─────┴4321 1 12321 121 1
...except this works in three dimensions instead of two!
Learn about spawning:
- The following applies to any difficulty, except for Easy.
- Every tile within 24 distance of the player is not eligible.
- Every tile outside a 144×144 square centered on you is not eligible.
- Every non-glass, non-half step surface in the outer world with 7 or less luminance is eligible for spawning.
- Every non-glass, non-half step surface in the Nether is eligible for spawning.
- Mob spawners cause mob to spawn at a high rate in any surface within 5 distance of it.
Here's what I try to do to ensure a luminance of 7 consistently along a line:
Place the first torch. Pardon my hexadecimal one-sided luminance graph:
Proceed until you find two tiles looking exactly like the next, then go back one.
Plant a torch there. Lo and behold, minimum luminance there will be 8!
You can adapt this algorithm to your necessities with ease. Just plant a torch in the darkest area when in doubt. (Duh.)
- Put torches directly onto surfaces for best results.
In your mining, be aware that any surface is good enough to spawn...
↓↓↓ ↓↓ All positions marked with an arrow are valid ███ ██↓ spawning points, to the best of my knowledge, █ █↓ and they all can lead to the just spawned mob █ █ to reach you. █ ↓█ █↓↓↓↓↓█ Be vigilant and don't mine caves from the ███████ bottom up :(
Learn how to keep mob that has spawned outside: make traps.
- Mobs can only jump up one tile. Make pits deeper than that and, once in, they will be trapped (skeletons are still dangerous and spiders can climb out).
- Mobs cannot deconstruct. Make walls. (Be aware creepers do explode, if they get close enough.) Use cobblestone: they have high explosion resistance and can't catch fire.
- Mobs cannot use items. Protect your entrance with a wooden door. Plant it from the outside, or skeletons will be able to hurt you with their arrows!
- Mobs' path finding is somewhat dumb. Protect your spawn point with water and liberal amounts of cactus (arrange them in a chequered pattern.)
The algorithm gives you the least amount of torches you can possibly use to get 8 minimum luminance in a row. That's the bare minimum, and it is useful to know: anything more than that will keep you safe.
I'm interested in what you said about glass and half-steps -- if I build a fortress out of these two materials, I'll be spawn-free even if I miss a torch or two? Also, does that only count half-steps that make a half-block-high surface, or can I stack two half-steps for a clean white floor (or as the step between a half step and a block+half-step step) and remain mob-free?
One question, just to confirm - so light from two sources is *not* additive? I would have thought that the light next to the "4" square would also be "4", from 3 + 1 from the "6".
@Cyclops Light is not addictive indeed -- and it isn't in "real life" either :) Lighting a torch under direct sunlight doesn't actually accomplish anything.
@badp, ah, yes, actually, light *is* additive in the real world :) Also, trains *can* reach velocities higher than 8 m/s, and leave piles, sadly, do not instantly decay. :)
@cyclops Light is additive in frequency certainly. If you wish to discuss this any further may I suggest physics.stackexchange.com? I unfortunately lack formal education in optics, or human perception thereof ;)