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This question stems from another question about how close torches need to be in order to prevent spawning (How far should I place torches in a planar huge room?).

The answers there seems to contain most of the rules you would need to know to arrive at a definitive answer:

  • Torches produce a light level of 14 in the block where they are located
  • Light falls off at a rate of one per block as you move away from the source
  • Mobs can spawn at a light level of 7 or less (8 would be required to prevent spawning)
  • Mobs can spawn in squares one or two above a solid block, so if torches are placed at ground level, their effective light level in a flat field scenario is 13 at the source, not 14

Answers to other questions provide further details:

This means that a square grid is not the most efficient layout; instead you'd want to use a staggered pattern (like the stars on the US flag).

As I put all this info together and go to write the question, my gut tells me the answer is "no", but I'll go ahead and ask anyway... Does light from multiple sources add together in any way?

In the real world, two light sources illuminating the same surface at the same time will produce an effective light level greater than either of them would individually... Rules in Minecraft are kept simple and only vaguely approximate the physics we are used to. In this case, does it simply compare all the levels contributed by various sources and assign the one that is greatest? That seems pretty consistent with the other rules, but can someone confirm this?

  • Just FYI : in real life light sources and sound sources are no additive either. Two lamps of level 14 in one place would make level 17 light. Those pesky decibels... – Barafu Albino May 14 '15 at 20:55
  • Snarky answer: they do add together in some way. If there are two sources that would produce light levels x and y in a cube, then the light level in that cube is the limit as n tends to infinity of (x^n+y^n)^(1/n). (This is, incidentally, why the max function is sometimes called the L-infinity norm, and when I first understood this it tickled me greatly.) – Daniel Wagner May 15 '15 at 1:28
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No, they don't.

Minecraft does indeed simply take the highest of the neighbouring voxels and subtract one to calculate the lighting level (unless it's a source of light, than that blocks light level is simply the light sources light level).

Both ice and water reduce the light level by 3 total each step (1 for the normal decrease and 2 extra). Some technically transparent blocks (transparent because they're not full blocks as far as rendering is concerned) completely block light, namely slabs, stairs and farmland.

Cobwebs and leaves stop the special "light source" that is the sun from going further down, meaning that from that point on normal rules apply to the sunlight.

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