Light

Light (or lighting) in Minecraft affects visibility, mob spawning, and plant growth. There are three aspects: light level, internal light-level, and rendered brightness.

Light level
Light levels can be found on the debug screen $$. There are two types of light: sky light and block light. There are 16 light levels, which are specified by an integer from 0 (the minimum) to 15 (the maximum).

Block light
Block light is from light-emitting blocks, which can spread using a kind of flood fill algorithm.

Spreading of block-light level decreases by one light-level for each meter (block) of distance from the light source. This applies to each of the 3 coordinate axis. In other words, light-level decreases diagonally by "taxicab distance", or the sum of the distance along each axis. For example:
 * If a torch (level 14) is placed on the floor, the light level on the adjacent floor blocks in all four directions is 13 while the diagonal blocks in all four directions has light level 12 (e.g. 14 minus 1 south, minus 1 east).
 * 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 away (i.e.- not touching the wall) has a light level of 11 (e.g. 14 minus 1 south, minus 1 east, minus 1 down).

Along a floor, this effect produces a diamond-shaped pattern of illumination around the light source. $$, light-filtering blocks can reduce more level of block light (See bellow).

$$, when calculating lighting, the shapes of some blocks are detected, including and only including piston, daylight detector, enchanting table, farmland, lectern, stonecutter, grass path, snow, end portal frame, slab and stair, so that the light passing through them can only spread in specific directions. For example, the grass path prevents the light from propagating downward, but the light can propagate in other directions.

Sky light
Sky-light brightness is 15 at an open-air place, then sky light can spread using a kind of flood fill algorithm. Note sky light is not reduced at night.

Opaque block can prevent the spread of sky-light. By contrast, some transparent blocks such as glass and iron bars have no effect on sky-light level. All other transparent blocks reduce the spread of sky light.

When the sky light of level 15 spreads down through a transparent block, the level remains unchanged. When it spreads downward through a light-filtering block (see bellow), it will attenuate some light level. When it spreads horizontally or upward, it will reduce 1 light level. The sky light with the level less than 15 is spreads as the block light - when it propagates to adjacent (including top and bottom, six blocks in total) blocks, it will be attenuated until it is 0.

$$, when calculating lighting, the shapes of some blocks are detected, including and only including piston, daylight detector, enchanting table, farmland, lectern, stonecutter, grass path, snow, end portal frame, slab, and stair. They have directional opacity, so that the light passing through them can only spread in specific directions. For example, the grass path prevents the light from propagating downward, but the light can propagate in other directions.

Light-filtering blocks
$$, all of light-filtering blocks decreases 1 level, which only includes end gateway portal, chorus flower, chorus plant, cobweb, frosted ice, ice, spawner, honey block, slime block, lava, water, bubble column, leaves, shulker box, beacon, and waterlogged transparent blocks.

The following values are the amount by which each block decreases the light level $$.

Light-emitting block


The following values are the brightness of the block itself:

Internal light-level
Internal light-level is used for the internal calculation of the game. The game uses the internal light-level of one block to compute some aspects, which affects mob spawning, plant growth, output of daylight detector and so on.

The game uses sky light, time, and weather to calculate a internal sky-light (also known as darkening sky-light), then take the maximum level of the block light and the internal sky-light as the internal light (formula: ). It's also an integer, which maximum level is 15. But it can be negative.

Here are lists of the levels of internal sky-light at sky light of level 15:

Effects of internal light
Note: Keep in mind that internal light-level is only one of the considerations that apply to mob spawning and plant growth.

Other
$$, the light in predicate is internal light-level.

Rendered brightness


The game uses the light level, time, and weather to compute the rendered brightness of a given block or a entity. Light is completely monochromatic and cannot be truly colored.

The rendered brightness of a block depends on both the level of block light and sky light. Sky light is not reduced at night, instead, the brightness curve itself changes based on the time. Entities cast circular/tridecagonal shadows; however, these are unrelated to the block rendering.

In general, lighting due to blocks results in a higher brightness, which is balanced by the fact that light due to blocks effectively starts at 14 (solid light-source blocks emit a level of 15, but that's for the light source block itself) while sky-light brightness is 15 outdoors. Light due to blocks also tends toward orange in the middle ranges, while sky light in the Overworld daytime is white.

In the Overworld with the "Moody" brightness setting, full daylight reaches 98% brightness, while at night brightness is reduced to about 17% and is shaded blue. Full darkness is about 5% brightness.

In the Nether, sky lighting doesn't play a role since there is no source of sky light (although if there were, it would reach about 99% brightness. ) Full darkness with the "Moody" brightness setting is at about 25% brightness, slightly darker than a block light level of 7 and no sky light in the Overworld, and is shaded orange like block light.

In the End, sky lighting wouldn't play a role even if there were a source of sky light; this can also be seen if lightning is summoned in the End, there is no flash of brightness like there is in other dimensions. Full darkness in the End with the "Moody" brightness setting is about 28% brightness, and is shaded toward a bluish-green rather than the orange of the Nether and of block lighting.

Smooth lighting


Smooth lighting (including ambient occlusion as well as interpolating lighting across block faces) is a lighting engine that blends light levels and darkens corners to add semi-realistic shadows and glowing from light sources. It affects only rendered brightness, not how blocks calculate their light level, so it has no effect on mob spawning or crop growth. It is set on by default. Paintings and water are unaffected.

$$, smooth lighting can be turned on or off in the Video settings, accessed from the Settings menu. $$, it has three settings: minimum, maximum, or off, and can be changed by accessing Video options from the Options menu.

Trivia

 * 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.