Dethrace

Dethrace is an attempt to learn how the 1997 driving/mayhem game Carmageddon works behind the scenes and rebuild it to run natively on modern systems.

Progress

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Last updated June 17 2024

• 92% of functions implemented
• Latest screenshot:

Background

Watcom debug symbols for an earlier internal build were discovered named DETHRSC.SYM on the Carmageddon Splat Pack expansion CD release. The symbols unfortunately did not match any known released executable, meaning they were interesting but not immediately usable to reverse engineer the game.

This is what it looked like from the Watcom debugger - the names of all the methods were present but the code location they were pointing to was junk:

CrayzKirk from the Carmageddon community picked it up and did a lot of painstaking work manually matching up many functions and data structures in the DOS executable to the debugging symbols.

We are slowly replacing the original assembly code with equivalent C code, function by function.

Is "dethrace" a typo?

No, well, I don't think so at least. The original files according to the symbol dump were stored in c:\DETHRACE, and the symbol file is called DETHSRC.SYM. Maybe they removed the "a" to be compatible with 8.3 filenames?

Game content

Dethrace does not ship with any content. You'll need access to the data from the original game. If you don't have an original CD then you can buy Carmageddon from GoG.com.

dethrace also supports the various freeware demos:

• Original Carmageddon demo
• Splat Pack demo
• Splat Pack Xmas demo

Building

Dependencies

Dethrace has a dependency on SDL2. The easiest way to install SDL is via your favorite package manager.

OSX:

brew install SDL2

Linux:

apt-get install libsdl2-dev

Point Dethrace at the Carmageddon install directory:

export DETHRACE_ROOT_DIR=/path/to/carmageddon

Clone

Dethrace uses git submodules, so we must pull them after the inital clone:

git clone https://github.com/dethrace-labs/dethrace
cd dethrace
git submodule update --init --recursive

Dethrace uses cmake for generating build files.

To generate the build files (generally only required once):

mkdir build
cd build
cmake ..

Once cmake has generated the build files for your platform, run the build. For example:

make

Running the game

Firstly, you need a copy of the Carmageddon game content. Extract the zip file if necessary.

Dethrace expects to be placed into the top level Carmageddon folder. You know you have the right folder when you see the original CARMA.EXE there. If you are on Windows, you must also place SDL2.dll in the same folder.

CD audio

Dethrace supports the GOG cd audio convention. If there is a MUSIC folder in the Carmageddon folder containing files Track02.ogg, Track03.ogg etc, then Dethrace will use those files in place of the original CD audio functions.

Changelog

From the beginning until release

Credits

• CrayzKirk (manually matching up functions and data structures in the executable to the debugging symbols)
• The developer at Stainless Software who left an old debugging .SYM file on the Splat Pack CD ;)

Legal

Dethrace is released to the Public Domain. The documentation and function provided by Dethrace may only be utilized with assets provided by ownership of Carmageddon.

The source code in this repository is for non-commerical use only. If you use the source code you may not charge others for access to it or any derivative work thereof.

Dethrace and any of its' maintainers are in no way associated with or endorsed by SCi, Stainless Software or THQ Nordic.