Light



Lighting (or Light) in Minecraft affects visibility, mob spawning, and plant growth. Lighting can be provided by sunlight, torches, glowstone, fire, lava, furnaces, Nether portals, End Rods and certain other objects.

Brightness
There are 16 light levels, which are specified by an integer from 0 (the minimum) to 15 (the maximum). The game uses the light level of a block to compute the brightness of a given block.

If the light level is 0, a block will be close to black. If the light level is 15, a white block will be close to white, while a red block will be red.

In the Overworld and the End, the brightness of a block decreases by 20% per light level. Note that this is an exponential decrease, so light level 13, for example, represents 64%, rather than 60%, of the maximum brightness. A light level of 0 corresponds to a brightness of 3.52%.

In the Nether, the brightness decreases by 10% per light level. For example, a light level of 13 equates to a brightness of 81%. A light level of 0 represents a brightness of 20.59%, approximately light level 8 in the Overworld.

Effects of light
When referring to this table, please note that "Level" indicates light level and "y: #" indicates y-axis (altitude) coordinates. Keep in mind that light level is only one of the considerations that apply to mob spawning and plant growth. Refer to each mob's wiki page for more details.

Light-emitting blocks


The following values are the brightness of the block itself:

Light Spread
The light from light-emitting blocks decreases by one light-level for each meter (block) of distance from the light source. Note that this applies to each of the 3 axes including N/S, E/W, and up/down. This fact is significant for preventing hostile mob spawning. If a torch (level 14) is placed on a wall two blocks up from the floor, the light level on the floor one block away from the wall will be 11 (e.g. 14 minus 2 down, minus 1 south). If the torch were placed on the floor at floor level, then the light level on the floor one block away from the wall will be 13 (e.g. 14 minus 0 down, minus 1 south).

Light decreases diagonally by "taxicab distance", or the sum of the distance along each axis. This means that if a torch (level 14) is placed on the floor, the light level on the adjacent floor blocks in all four direction will be 13 while the diagonal blocks in all four directions will have light level 12 (e.g. 14 minus 1 south, minus 1 east). Along a floor, this effect produces a diamond-shaped pattern of illumination around the light source. Remember, light decrease takes place in three dimensions. This means that if a torch (level 14) is placed on a wall one block up from the floor, then the block on the floor that is diagonally one block way will have a light level of 11 (e.g. 14 minus 1 south, minus 1 east, minus 1 down).

The minimum number of light sources needed to prevent hostile mob spawning in the Overworld is difficult to determine because light decreases in all three dimensions. Given a perfectly flat plane or floor, the cheapest and easiest solution is to place torches on the floor in a diamond pattern, with a torch every 6th block (5 blocks in-between each torch diagonally).

''Note: To get a nicer looking surface, these torches can be replaced with glowstone or pumpkin lanterns embedded into the floor. The same pattern may be used even though this reduces the light level on the floor by 1. This is because the glowstone and lanterns are 1 light level stronger than torches.''

Here, the yellow "T" represents a torch on the floor, and number is the light level of adjacent floor blocks. Note that no block is less than light level 8, which means that hostile mobs cannot spawn. The green is only to highlight the 5 blocks between each torch.

To safely light hallways (or straight tunnels in a mine) using the same technique depends on the width of the hall. For a single block wide hall, the torches may be placed up to 13 blocks apart. A 3-block hall requires torches every 11 blocks down the center while a 5-block hall needs them every 9 blocks. An even numbered width hallway must have them staggered since there is no center row. For a 2-block hall, space them 12 blocks (plus 1 block offset.) A 4-block hall needs them every 10 blocks plus offset. A 6-block hall requires them to be spaced every 8 blocks and this works whether they are offset by 1 or 3 blocks, or even if they are placed against the walls. For halls that are 7 blocks wide, simply use the pattern above. For wider 'halls' you can adapt the same pattern. Just realize that this pattern requires torches to be placed right against the walls for complete coverage. If you wish to use glowstone, lanterns or redstone torches in the ceiling, you must space them closer according to the height of the hall. Place them closer by twice the height. E.g., instead of 13 blocks in a 1-block hall, if it is 2 blocks high, place them 9 blocks apart (13 - 2 - 2.)

However, when outdoors, if the ground level changes by even one block, this decreases light further, requiring a different pattern. Additionally, when indoors it may be more aesthetically pleasing to light sources along walls or attached to the ceiling. But this means that the light level will decrease from ceiling to floor, and the light level of the floor is used to calculate mobs spawning.

Light-filtering blocks


Opaque blocks prevent the spread of light while glass and portal interiors have no effect on light level.

All other transparent blocks reduce the spread of light. The following values are the amount each block decreases the light value. The light emitted decreases by one for each block of distance from the light source, more depending on the block through which it passes.

Leaves and cobwebs do not have any extra effect on block light, but they do diffuse sky light. The light level from sunlight or moonlight is the same in each block of air in the column of air above the highest obstruction in the column. When placed, leaves and cobwebs obstruct that light column so that the lowest air block above the leaves acts as other light sources do. As you descend below the leaves, the light level diminishes with distance like it would from other light sources such as torches. To control this effect, create an opaque 1×1 chimney with leaves at its opening above you.

Smooth lighting
Smooth lighting (which includes ambient occlusion as well as interpolating lighting across block faces) is the lighting engine added in Beta 1.3, with the help of MrMessiah. This lighting engine is set on by default, and can be set to minimum, maximum, or off by accessing Video Options from the Options menu.

The engine blends lighting to add semi-realistic shadows and glowing from light sources. It darkens inside corners, resulting in small spaces appearing much darker. Before Beta 1.3, the feature could only be obtained by modifying the game with the help of MrMessiah's BetterLight mod.

The "Maximum" smooth lighting toggle fixes bugs with stairs. However, this is an optional toggle. The "Minimum" toggle increases performance, but does not fix the bug.

History
Minecraft has an extensive history when it comes to lighting. Classic's lighting model is simple and only checks whether a block is exposed to the sky. Indev's model is more complex and considers a block’s distance from the nearest sunlight and from the nearest light-emitting block. Alpha’s model is a refinement of Indev's, calculating sunlight and block-emitted light separately and using a different scale of light intensities. An earlier Beta update improved upon Alpha's model by adding the smooth lighting option, and in a later Beta update, the whole lighting engine was again rewritten to be much more efficient, have more detail, and be smooth in transition of lighting differentials.



Trivia

 * Hostile mobs can spawn in areas where there should be light, but there isn't. This is because the game thinks there is a light level of 0.
 * Smooth Lighting is not apparent on the top of water or on paintings.
 * A 21×21 square of opaque material is enough to spawn mobs in the shadow underneath.
 * If zombies or skeletons are in water or in the low light levels caused by trees, they can survive through the daytime.
 * In Minecraft's source code, the luminescences are defined using the floating point values in the third column. In a weird quirk, these floating point numbers are fractions of 16, but are multiplied by 15 to get the integer light value. This means that both 0/16 and 1/16 (0.0 and 0.0625) correspond to the integer light value 0.