Template:Lit Radius

Calculates the max distance of tiles away from a light source that tiles can be before they fall below 30% light (lit). This value rounded down is the last tile in a straight line that will count as lit - this distance doesn't include the light source's tile itself.

Parameters

• 1: glowRadius of the light source (e.g. 12 for standing lamp)
• 2: sum of the glowColor (e.g. 217+217+208 for standing lamp)
• 3: target light level - defaults to 0.3, which is all you probably want

Examples

Example: {{Lit Radius|12|{{#expr:217+217+208}}}} -> 9.092558072384

Combine with #expr round to improve readability: {{#expr: {{Lit Radius|12|{{#expr:217+217+208}}}} round 2}} -> 9.09

Maths

The light value (glow) a certain distance away from a light source is determined as a combination of a linear decay based on distance relative to glowRadius (a), and the inverse of the distance squared (b). These two numbers are combined with 60% from (a) and 40% from (b) to give a multiplier (f) to the sum of the glowColors, which then directly determines the light value at the tile.

r = glowRadius 
d = distance + 1
c = sum(glowColors)

a = 1 - d/r
b = 1/(d*d)
f = a + (b-a)*0.4

glow = max(0, min(0.5, f*c/3/255*3.6))

The middle equations can be rearranged into a cubic equation in (d) in terms of (r) and (f), and the bottom equation can be rearranged for (f) in terms of (c) and (glow), provided 0 < (glow) < 0.5:

0 = -r*2/3 + r*(f*5/3 - 1)*d^2 + d^3

f = glow/c*3*255/3.6

This template substitutes (f) into the cubic equation and solves it using Cardano's algorithm.