Revisiting SimCity 2000

Looking Under the Hood - Continued

In this post I will delve into the details of extracting useful information from our .SC2 file.

Directly referencing David Moew’s guide…

Each segment has an 8-byte header:

Bytes 1-4: Type of segment
Byres[sic] 5-8: Number of bytes in this segment, except for this 8-byte header

The remaining bytes in each segment are data.

The data in most SimCity segments is compressed using a form of run-length
encoding.  When this is done, the data in the segment consists of a series
of chunks of two kinds.  The first kind of chunk has first byte from 1 to
127;  in this case the first byte is a count telling how many data bytes
follow.  The second kind of chunk has first byte from 129 to 255.  In this
case, if you subtract 127 from the first byte, you get a count telling how
many times the following single data byte is repeated.  Chunks with first
byte 0 or 128 never seem to occur.

David also provides a primer for the segment types:

SimCity files consist of the following segment types, in order, with the
following lengths.  Except as noted, segments are compressed as above, and
the length given for them is the length after uncompression; the compressed
length may vary.

Segment type     Length

MISC              4800    
ALTM             32768  (uncompressed)
XTER             16384    
XBLD             16384    
XZON             16384    
XUND             16384    
XTXT             16384    
XLAB              6400    
XMIC              1200    
XTHG               480    
XBIT             16384    
XTRF              4096    
XPLT              4096    
XVAL              4096    
XCRM              4096    
XPLC              1024    
XFIR              1024    
XPOP              1024    
XROG              1024    
XGRP              3328    
CNAM                32  (uncompressed; optional?)

Below is an explanation of each segment’s purpose. I have separated the segments into three categories: Known & Useful, Known & Not Useful, and Unknown.

Known & Useful

Segment     Description
 CNAM:      City name (technically useful, although trivial)
 MISC:      Miscellaneous city data.
 XBIT:      Flags for each terrain square identifying access to utilties, water, etc
 XBLD:      Square content identifier (buildings, trees, rubble, etc)
 XUND:      Identifies what's underneath each square (subway, pipes, etc)
XZONE:      Square zoning & density identifier
 XTXT:      Square Microsimulator flag. (Park System Microsim, Police Microsim, etc)
 XLAB:      Labels. Label 00 is the Mayor name. (possibly useful)
 XMIC:      Microsimulator records.
 XPLC:      Police power
 XPOP:      Population map
 XROG:      Rate of growth of population
 XPLT:      Pollution
 XVAL:      Property values
 XCRM:      Crime rate
 XTRF:      Traffic

Known & Not Useful

Segment     Description
 ALTM:      Altitude map
 XTER:      Terrain information for tiles including water coverage and slope.
 XFIR:      Firefighting power

Unknown

Segment     Description
 XGRP:      32*104 bytes long.
 XTHG:      480 bytes long.

I placed ALTM, XTER, and XFIR in the “Not Useful” category because for purposes of our analysis, we don’t really care about water coverage, slope, or how robust a city’s firefighting coverage is. Generally, we assume this to be binary - either a city can fight fires, or it can’t. Obviously this is a huge over-simplification, however for the sake of sanity and timeliness, I’d like to first focus on the obvious variables.

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Revisiting SimCity 2000 - Episode II

A Data Scientist's Approach (cont'd)

Looking Under the Hood - Continued

Note: If this post appears to abruptly end, it’s because it’s currently being developed. More content will appear later. If not, this message will change.