Awesome

DOOM-CRT

One thing I’ve wanted to do for some time, is take the original source code release for DOOM, the one that only had linux support, and make my own port to windows, utilizing my single header libs and putting my crt filter on top of it. This is that thing.

Now, there are a lot of great windows ports, fixing bugs and adding features, and most of them would be a better choice if you want a DOOM which runs well on windows, or if you want some code to do serious work on top of. My port won’t try to compete with those efforts.

The main reason I’m doing it is for my own enjoyment. I’ve never really poked around in the DOOM code properly before, but always wanted to.

And also, I think it might be useful to make available a simple and minimalistic port. One which modifies the original code as little as possible, uses as few dependencies as possible (no large external frameworks) and which can be built without a complex build system.

It is not using any large frameworks, but relies on a few stb-style single-file header-only libraries (which are all placed in the libs_win32 folder) which I have written myself - with the notable exception of the TinySoundFont library, which is used as a back-end for music playback.

It’s not a particularly nice port, quick and dirty is more like it. Feel free to fork it and clean it up if you want to :-)

I had to make a few extra changes to make it so you can build it to WASM for running in a browser, but those changes are contained to a single commit, so if you don't want them, just checkout the commit prior to that one.

You can try this version in your browser here: https://mattiasgustavsson.com/wasm/doom-crt

How to build

To build, start a visual studio developer command prompt and run the command:

cl doom.c

This should give you a runnable doom.exe. The wad file for the shareware version is in the repo as well, so you should be good to run the exe straight away. Enjoy!

You can also build with Tiny C Compiler:

tcc\tcc doom.c

You can download tcc here: tiny-c-compiler for either 32 or 64 bit Windows. Unzip it so that the tcc folder in the zip file is at your repository root.

It can also be built into an HTML file to run in a browser, using WAjic:

wasm\node wasm\wajicup.js doom.c doom.html -embed doom1.wad doom1.wad -rle -template template.html

A WebAssembly build environment is required. You can download it (for Windows) here: wasm-build-tools-win. Unzip it so that the wasm folder in the zip file is at your repository root.

The wasm build environment is a compact distribution of node, clang/wasm-ld, WAjic and wasm system libraries.

/Mattias Gustavsson

ORIGINAL README FROM ORIGINAL SOURCE CODE RELEASE FOLLOWS

Here it is, at long last. The DOOM source code is released for your non-profit use. You still need real DOOM data to work with this code. If you don't actually own a real copy of one of the DOOMs, you should still be able to find them at software stores.

Many thanks to Bernd Kreimeier for taking the time to clean up the project and make sure that it actually works. Projects tends to rot if you leave it alone for a few years, and it takes effort for someone to deal with it again.

The bad news: this code only compiles and runs on linux. We couldn't release the dos code because of a copyrighted sound library we used (wow, was that a mistake -- I write my own sound code now), and I honestly don't even know what happened to the port that microsoft did to windows.

Still, the code is quite portable, and it should be straightforward to bring it up on just about any platform.

I wrote this code a long, long time ago, and there are plenty of things that seem downright silly in retrospect (using polar coordinates for clipping comes to mind), but overall it should still be a usefull base to experiment and build on.

The basic rendering concept -- horizontal and vertical lines of constant Z with fixed light shading per band was dead-on, but the implementation could be improved dramatically from the original code if it were revisited. The way the rendering proceded from walls to floors to sprites could be collapsed into a single front-to-back walk of the bsp tree to collect information, then draw all the contents of a subsector on the way back up the tree. It requires treating floors and ceilings as polygons, rather than just the gaps between walls, and it requires clipping sprite billboards into subsector fragments, but it would be The Right Thing.

The movement and line of sight checking against the lines is one of the bigger misses that I look back on. It is messy code that had some failure cases, and there was a vastly simpler (and faster) solution sitting in front of my face. I used the BSP tree for rendering things, but I didn't realize at the time that it could also be used for environment testing. Replacing the line of sight test with a bsp line clip would be pretty easy. Sweeping volumes for movement gets a bit tougher, and touches on many of the challenges faced in quake / quake2 with edge bevels on polyhedrons.

Some project ideas:

Port it to your favorite operating system.

Add some rendering features -- transparency, look up / down, slopes, etc.

Add some game features -- weapons, jumping, ducking, flying, etc.

Create a packet server based internet game.

Create a client / server based internet game.

Do a 3D accelerated version. On modern hardware (fast pentium + 3DFX) you probably wouldn't even need to be clever -- you could just draw the entire level and get reasonable speed. With a touch of effort, it should easily lock at 60 fps (well, there are some issues with DOOM's 35 hz timebase...). The biggest issues would probably be the non-power of two texture sizes and the walls composed of multiple textures.

I don't have a real good guess at how many people are going to be playing with this, but if significant projects are undertaken, it would be cool to see a level of community cooperation. I know that most early projects are going to be rough hacks done in isolation, but I would be very pleased to see a coordinated 'net release of an improved, backwards compatable version of DOOM on multiple platforms next year.

Have fun.

John Carmack 12-23-97