1.5 KiB
| title | date | draft |
|---|---|---|
| Nethack's Level Generation | 2023-02-05T09:08:07-08:00 | true |
I recently became interested in how Nethack generates levels. It has a distinctive feel that's uniquely Nethack, and that can't be perfectly replicated with "room and corridor" algorithms that I've studied so far. Nethack's source code is freely available on Github, though as I discovered while researching for this article, having it available doesn't mean it's easy to understand.
I'm basing this entire series on the Nethack 3.6 branch.
Basics
It's written in C, using C89 style function declarations. You see a lot of functions defined like this, with the types of arguments defined below the function declaration:
int
a_function(a, b, c)
int a, b;
char c
{
// ...
}
The standard Dungeons of Doom map style is a hallmark of Nethack, Hack, and Rogue. Given this long lineage, the map generator is (I suspect) one of the older parts of the codebase. A lot of the architectural decisions reflect a differen time and place: it strives to be extremely memory and CPU efficient, reuses global in-memory structures rather than declaring new ones, and generally makes due with less as often as possible. This includes variable names too.
Most of this happens in mklev.c.
Levels are always 80 columns by 21 rows in size.