• Jim Hohorst (13/13) Nov 04 2016 I'm interested in generating new maps for Empire (outside of the
• Jim Hyslop (33/46) Nov 20 2016 Hi,
• Jim Hyslop (18/25) Dec 25 2016 Hi, again!

Jim Hohorst <jim hohorst.net> writes:

I'm interested in generating new maps for Empire (outside of the 
map editor) and have been trying to figure out the file format.  
I've figured out the structure of the map itself, but after the 
map data there come a series of bytes separated by 0s.  As they 
match the number of cities on the map, I assume they have 
something to do with them, but haven't been able to understand 
the purpose. I would have thought they somehow indicated whether 
the city was on the water (and could build ships) and whether it 
could be a starting place for a game (not on single-city 
islands), but don't see any pattern (unless I'm reading them from 
the wrong direction).

Anyone know more about how the map files are structured?  I'm 
using Version 2.05c through DosBox on a Windows 10 machine.

Jim Hyslop <jhyslop dreampossible.ca> writes:

On Saturday, 5 November 2016 at 03:35:16 UTC, Jim Hohorst wrote:
 I'm interested in generating new maps for Empire (outside of 
 the map editor) and have been trying to figure out the file 
 format.  I've figured out the structure of the map itself, but 
 after the map data there come a series of bytes separated by 
 0s.  As they match the number of cities on the map, I assume 
 they have something to do with them, but haven't been able to 
 understand the purpose. I would have thought they somehow 
 indicated whether the city was on the water (and could build 
 ships) and whether it could be a starting place for a game (not 
 on single-city islands), but don't see any pattern (unless I'm 
 reading them from the wrong direction).

 Anyone know more about how the map files are structured?  I'm 
 using Version 2.05c through DosBox on a Windows 10 machine.

Hi,

I don't know about 2.05c, but I have downloaded and examined the 
source for 2.03. This may or may not help, I don't know.

The format for 2.03 is a form of Run Length Encoding. The two 
least significant bits encode the map element (1=City, 2=Sea, 
3=Land). The other six bits encode the number of sequential tiles 
of that element. Add 1 to the six-bit value to get the value. In 
C, you would write

int type;
int number;

number = (mapbyte >> 2 ) & 63;
type = mapbyte & 3;

The map data starts at the bottom right corner and works from 
right to left, bottom to top. A byte with the value 0 signifies 
the end of the data.

Here are the first couple of rows from Map A:
ubyte aDotMap[] =
[
	0x1a,0x13,0x06,0x13,0x36,0x07,0x76,0x07,
	0x06,0x1b,0x02,0x0f,0x66,0x2f,0xb2,0x2f,

0x1a: >> 2 gives 6; & 3 gives 2; so it is a sequence of 7 sea 
tiles
0x13: >> 2 gives 4; & 3 gives 3; so it is a sequence of 5 land 
tiles
and so on.

The map data is stored in a single-dimension array. The 
row/column numbering is inferred from the position within the 
array: Row is position/100, and column is position%100. 
Conversely, position = row*100 + column.

As I said, I don't know how much this will help, as it sounds 
like the map format has changed between 2.03 and 2.05c. This 
might give you some clues, though.

Jim Hyslop <jhyslop dreampossible.ca> writes:

On Saturday, 5 November 2016 at 03:35:16 UTC, Jim Hohorst wrote:
 I'm interested in generating new maps for Empire (outside of 
 the map editor) and have been trying to figure out the file 
 format.  I've figured out the structure of the map itself, but 
 after the map data there come a series of bytes separated by 
 0s.  As they match the number of cities on the map, I assume 
 they have something to do with them, but haven't been able to 
 understand the purpose.

Hi, again!

I found 2.05C on abandonia.com and downloaded it. Ahhh, that's 
the game I remember!

Anyway, I examined the map files and played with the built-in map 
generator. The extra bytes at the end of the file seem to 
indicate how many cities are on each continent. I'm guessing the 
first pair of bytes corresponds to the first city encountered 
(going from left-to-right, top-to-bottom), the second pair 
corresponds to the second city, and so on. Since you can have 
more than 256 cities on a map (and therefore on a continent), you 
need two bytes for the count. It appears to be stored big-endian, 
i.e. most-significant byte first.

For example, suppose you have two continents - one at the top of 
the map and one at the bottom. The top continent has 4 cities, 
and the bottom continent has 5. I would expect the last 18 bytes 
to be:

04 00 04 00 04 00 04 00 05 00 05 00 05 00 05 00 05 00