Organise Lighting Rendering

[olls]

Related to #109.

Idea for simplifying the rendering of lights:

• Use a buffer to store the lightness value for every block, calculated from the max of:
  • Lights (passed in from python)
  • Day value, fading to 0 at the ground
  • Sun (not moon), when sun is above ground height and not behind a solid block
• Also store the calculated background colour of lights in the buffer (as max of the lightness for each pixel), looking up the pixel in map to mask solid areas off
• Add the blocks to the pixel buffer, using the lightness and colour buffer (for clear backgrounds)
• If the pixel is clear and there is no colour in the background buffer, use the default sky colour:
  • Above ground height is day/night colour
  • Below ground height is default cave colour

[olls]

Definition of light Z value:

• z = -2 are not added to the lighting buffer as they are just graphical lights, like the moon.
• z = -1 are added to the lighting buffer IF the source is above the ground, and not behind a solid block.
• z = 0 are always added to the lighting buffer.

[olls]

https://github.com/itsapi/pycraft/tree/lighting-framebuffer

[olls]

Woo! Speed increase is 5x with around 10 torches on the screen (Very rough: https://docs.google.com/spreadsheets/d/1k7WmXYKTU5azjU4hnFJVy2Sc1SgqH14uuJU_IvflRaU/edit?usp=sharing). Speed difference should go up with no. torches.

Time complexity is roughly something like: (I think...)

• old version: O(pixels*(torches^2)) at minimum
• new version: O(torches+pixels)