Lighting
This section will go into how lighting data is rendered and calculated.
Light-spread
Lighting in Minecraft is calculated via a Four-way flood fill algorithm. The idea is simple, propogate a value out from a central point until you're done. In Minecrafts case, the limit of the flood fill is when the light-level reaches 0.
The fact its a Four-way flood fill is apparent due to the characteristic diamond shape this results in.
Sky light
Sky light is always at a level of 15 when the sky is unobstructed. If any semi-transparent blocks are passed through as the lighting propagates, it'll lose some light*.
Then lighting is spread horizontally, seeping into caves and similar.
If a greater light-value is encountered, it'll win out. Darkness can become brighter, but lightness can never become darker.
MISSING
* How much?
Block light
Block lights work similarly, though they spread out from the lightsource instead of the sky. Additionally their light has a falloff applied in all 6 directions*, reducing the light level by 1 with every block away from the lightsource.
* North, East, South, West, Up, Down
Face lighting
Every block has constant directional lighting which is statically assigned based on the angles of the faces. This is the base of all lighting thereafter, no matter whether it's smooth or not.
NOTE
I haven't found a generalized formula to this yet but I'm sure there is one
if (normal.y > 0.0f) {
lighting = 1.0f;
} else if (normal.y < 0.0f) {
lighting = 0.5f;
} else {
lighting = (abs(normal.x) * 0.6) + (abs(normal.z) * 0.8);
}Source: Betrock
The resulting value is then multiplied with the underlying color.
Light levels
Lighting in Minecraft is based on a 4-bit gradient from 0 - 15. As of Indev, this relationship is no longer linear.
Each brightness value below 15 is 80% as bright as the one above it. For example, 14 is 80% as bright as 15, and 13 is 64% as bright as 15. (Taken from the Minecraft Wiki)
If mapped from a range of 0.0 - 1.0, where 1.0 represents a light level of 15, we get the following mapping.
| Value | Color |
|---|---|
| 0 | 0.035 |
| 1 | 0.044 |
| 2 | 0.055 |
| 3 | 0.069 |
| 4 | 0.086 |
| 5 | 0.107 |
| 6 | 0.134 |
| 7 | 0.168 |
| 8 | 0.21 |
| 9 | 0.262 |
| 10 | 0.328 |
| 11 | 0.41 |
| 12 | 0.512 |
| 13 | 0.64 |
| 14 | 0.8 |
| 15 | 1.0 |
Or in code form
const float lightArray[16] = { 0.035f, 0.044f, 0.055f, 0.069f, 0.086f, 0.107f, 0.134f, 0.168f, 0.21f, 0.262f, 0.328f, 0.41f, 0.512f, 0.64f, 0.8f, 1.0f };Non-smooth lighting
The illumination of a face is determined by the light level of the block its facing, i.e. the top of a grass block with a torch on it would get the full light level of 14.
Smooth Lighting
Every vertex samples and averages the light level of surrounding blocks along the direction of the face its part of. This provides ambient occlusion without any additional work, since solid blocks have a total light level of 0.
