Since I left my job at Amazon I have spent a lot of time reading great source code. Having exhausted the insanely good idSoftware pool, the next thing to read was one of the greatest game of all time : Duke Nukem 3D and the engine powering it named "Build".
It turned out to be a difficult experience: The engine delivered great value and ranked high in terms of speed, stability and memory consumption but my enthousiasm met a source code controversial in terms of organization, best practices and comments/documentation. This reading session taught me a lot about code legacy and what helps a software live long.
As usual I cleaned up my notes into an article. I hope it will inspire some of us to read more source code and become better engineers.
Part 1: Overview.
Part 2: Engine Internals.
Part 3: Engine legacy.
Part 4: Chocolate Duke Nukem 3D.
Genesis
Duke Nukem 3D is not one codebase but two :
Build engine: Providing rendition, network, filesystem and caching services.
Game Module: Using Build's services in order to generate a gaming experience.
Why such a division? Because back in 1993, when development started, very few people had the skills and dedication to produce a good 3D engine. When 3D Realms decided to write a game that would challenge Doom, they had to find the technology that would power it. That is where Ken Silverman enters the picture.
According to his well-documented website and interview, Ken Silverman (18 years old at the time) wrote a 3D engine at home and sent a demo for evaluation to 3D Realms. They found his skills promising and worked out a deal:
Silverman would write a new engine for 3D Realms but he would keep the source code. He would only deliver a binary static library (Engine.OBJ) with an Engine.h header file. The 3D Realms team on their side would take care of developing the Game module (Game.OBJ) and would also release the final executable DUKE3D.EXE.
Unfortunately both part of the game were not open sourced simultaneously:
The Engine module source code was released by Ken Silverman on June 20, 2000 .
The Game module source code was released by 3D Realms on April 1, 2003.
As a result the full source code was available 7 years after the game was released.
Trivia : The name of the engine "Build" was chosen by Ken Silverman when creating the directory for the new engine: He used a thesaurus to search for a synonyms of "Construction".
