For a Civilization-like game I liked to play (freeware, playable, but not updated anymore https://visualbruno.itch.io/world-of-empires2 ) I wanted to create better maps. As Civilization used to be a simple squares-based map, I found Excel an easy and visual tool to get this done. This article is about the map creator I made. The link to the tool is at the bottom. This is an example of what the tool generates:
Using just excel functions the tool can create a 64x48 tiles map. The tool does not use macros. It has to have a random factor, but should be deterministic in its outcome. As in: you can pick a random seed, but given the same seed, it should give the same outcome.
As a base for the map, I started off with one cell where the user has to put in a "seed value", a number greater than 0 which is the base for the whole map. Based on this seed and the dimensions of the map, the grid is filled with pseudo-random numbers. In Excel function:
=MOD(48271*A1,2^31-1) - this is the Lehmer random number generator
Standardize these values to the range 0-1, so they can be used easier. I added some conditional formatting for easier visual checks.
The next step is to use these random numbers to create land and sea. For this we need one more extra input: the percentage of land that the user wants. The issue is that the map just based on the random numbers from Step 2 looks like this (top 40% of random values are land here):
value(i0,j0)*(1-vert_blend)*(1-horiz_blend)+value(i0,j1)*(vert_blend)*(1-horiz_blend)+value(i1,j0)*(1-vert_blend)*(horiz_blend)+value(i1,j1)*(vert_blend)*(horiz_blend)0,00*(1-0,75)*(1-0,5)+0,43*(0,75)*(1-0,5)+0,71*(1-0,75)*(1-0,5)+0,70*(0,75)*(0,5)=0,51
The 4th step is merging these 5 random maps. Again: I am basically creating a height map, so only the e.g. top 40% of random values becomes land, the rest sea. The main challenge here is the weighing factor per map. If I want a pangea map (one big landmass), I want to give the 4th octave a big weight, the lower ones less. What I came up with are 2 factors: the maximum octave used (0 is the random numbers I started with) and the octave multiplier: starting with a weight of 1 for octave 0, the next octave weight gets multiplied by this number. The results of these steps becomes apparent in step 5.
Step 5 is setting the landmass percentage, as said above: only the e.g. top 40% of random values of step 4 become land, the rest sea. With 40%, this is the impact of the settings of step 4:
Step 6 is a small smoothening: removing the single tile water or land. Basically: if all tiles around it are water, then the tile itself should be water.
Mountains & lakes... Say the top 1% of the height map (step 5) should be mountain. For lakes: every water tile that has at least 2 land tiles next to it becomes a lake. After step 6&7, this is the land (light green), lake (blue), sea (white) & mountain (dark green) map.
Climate... Here I have 2 inputs: rainfall (0: little, 9: lots) and temperature (0: cold, 9: hot). But how does this translate into different tile types? For that I created a small table for the different types of terrain, their min&max temperature (scale: 0-100) and min&max rainfall (0-100).
This one is rather easy: it runs from 0 at the poles to 100 at the equator. One small adjustment: when the temperature is set to "cold" (=0), it runs from 0 to 90 and when it's set to hot (=9) it runs from 9 to 99.
In my tool I'm basically using a Perlin noise map with an octave of 1,5. I'm using the resulting (random) numbers for 80% and add the setting for rainfall for 20%, so a "very wet" map will be in the range of 20-100 and a very dry map will be 0-80. This leads clusters of wet and dry, e.g.:
The next step is to find out if a terrain type can exist on a certain cell in the grid. That's not too complicated with the temperature and the rainfall already calculated. But it can happen that based on these 2 criteria multiple terrain types can occur on one cell, so I needed some pseudo random variable to determine the final terrain type. Again: I want the system to be deterministic and always lead to the same answer. So what I did is to take the random values of step 2 and for every terrain type, I took the next chunck of that random value, like so:
Random value from step 2: 0,78252378
Tundra (from digit 2): 0,8252378
Grassland (from digit 3): 0,252378
Plains (from digit 4): 0,52378
Etcetera... In that way, I have the temperature & rainfall to filter out which terrain types are possible and a pseudo random factor to act as a tie-breaker if more terrain types are possible.
PUBLISHED before on: https://steemit.com/map/@beeheap/create-a-fantasy-grid-map-in-excel
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