Custom maps the AI can function on

In working on MapCopy I became obsessed with figuring out how Civ 2 calculates fertility. My obsession didn't last long enough to figure it all out, but here's what I found.

As Wobbegong posted, the tile itself, the inner city radius ring and outer city radius ring are weighted differently. So the total food/shield/trade production is calculated like:

Code:
total production = (self production * 4) + 
                   (inner ring production * 2) + 
                   (outer ring production)

The production for each square is from RULES.TXT, except when calculating shields for grassland squares. A grassland square with a shield has production of 1 with regards to fertility. If there is no shield, then the grassland square has a shield production of 0 with regards to fertility. The value in RULES.TXT for grassland shield production does not seem to affect fertility.

If a square can be irrigated a bonus is added to its food production. The value seems to be the floating point representation of 2/3. Note that the full floating point representation is needed. 0.67 is not good enough. For mining, a bonus of 0.5 is added to shield production. I'm a little suspicious of these values because I discovered them empircally. There could very well be test cases that I didn't try which disprove these values. Note that the value of the irrigation/mining bonus in RULES.txt does not matter, it can be 0 and the bonuses above are still used for calculating fertility. Also, if a square supports both mining and irrigation, then only the irrigation bonus applies for calculating fertility.

The fertility value is then calculated using the following formula, rounded to the nearest integer:

Code:
(total food * 3) + (total shields * 2) + (total trade) 
------------------------------------------------------
                           16

Then there is another special case. If the square in question is a grassland without a shield, the fertility is decremented by 1. Finally the fertility value is forced to be between 8 and 15.

In all of my tests, this seems to work, but there's probably a test case out there that disproves me. Also, all of my tests have been done with special resources supressed. I didn't have time to figure out how resources affect fertility.
 
Dusty said:
My obsession didn't last long enough to figure it all out...
All too familiar. ;)

Dusty said:
In all of my tests, this seems to work, but there's probably a test case out there that disproves me. Also, all of my tests have been done with special resources supressed. I didn't have time to figure out how resources affect fertility.
I should compare these results with some of mine - it may help iron out a few things - but I've been a bit of a Civ2 bum in recent times. :D
 
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