Primer on torch placement in Minecraft

[ElectricSheepDreams]

Okay, this is for any forum member wishing to light an area to keep mobs from spawning...or wishing to build a Mob Spawner:

Sunlight, lava and fire give a block a light value of 15 and torches 14 -1 per space. 

Mobs SPAWN on certain blocks* when the light lvl is 7

Thus unless you wish to pave your entire area with Glass blocks ( other blocks are available ), one needs place torches so that the light lvls remain above 7.  Easy, peasy, yes? Not exactly as torches light in a diamond pattern. For maximum coverage, you should tessellate.  Offsetting the torches, allows for an extra space between them :

XX XX XX XX XX XX 08  XX XX XX XX XX XX

XX XX XX XX XX 08 09 08 XX XX XX XX XX

XX XX XX XX  08 09 10 09 08 XX XX XX XX

XX XX XX 08 90 10 11 10 09 08 XX XX XX

XX XX 08 09 10 11 12  11 10 09 08 XX XX

XX 08 09 10 11 12 13 12 11 10 09 08 XX

08 09 10 11 12 13 TT 13 12 11 10 09 08

XX 08 09 10 11 12 13 12  11 10 09 08 XX 

XX XX 08 09 10 11 12 11 10 09 08 XX XX 

XX XX XX 08 09 10 11 10 09 08 XX XX XX

XX XX XX XX 08 09 10 09 08 XX XX XX XX

XX XX XX XX XX 08 09 08 XX XX XX XX XX

XX XX XX XX XX XX 08 XX XX XX XX XX XX

NOTE:  This is for flat surface lighting bleed off values of -1 per block. Changes in elevation affect lighting values and should be taken into account.  When in doubt, check the light value for the block in question and adjust torch placement as needed ( 8 or Above ).  .

* Mobs can NOT spawn on a block with:

Light level 8

fences

repeaters

CLOSED gates**

CLOSED trap doors**

tilled earth**

slabs ( of any  kind)**

Stairs ( of any kind) **]

 Carpet **

** due to height variance 

beds

chests

pressure plates

levers

buttons

rails

Any block you considered a transparent block : Glass, iron bars, cobwebs, leaves and lava.

Edited June 3, 2019 by ElectricSheepDreams

[JeffreyEpstein]

TL; DR