id_notes/John C/1997-12-23

[idsoftware.com]

Welcome to id Software's Finger Service V1.4!

Name: John Carmack

Email: johnc@idsoftware.com

Description: Programmer

Project: Quake 2

Last Updated: 12/23/1997 09:19:45 (Central Standard Time)

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Dec 23:

The DOOM source is up.

Merry christmas!

ftp://ftp.idsoftware.com/idstuff/source/doomsrc.zip

---- contents of README.TXT -----

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....

...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