Doom3 is the proof that “keep it simple” works

http://www.gamedev.net/page/resources/_/technical/game-programming/doom3-is-the-proof-that-keep-it-simple-works-r4009

by GeekandProud • 11 years ago

201 108 11 years ago

I felt the same after reading all of ids engines source code, such as Quake 1-3. Those were C only, however.

onion2k• 11 years ago

If you read this article and agreed with it, you should definitely read this next: http://lesswrong.com/lw/dr/generalizing_from_one_example/

Angostura• 11 years ago

I think you meant "If you only read the headline and agreed with it".

s3cur3• 11 years ago

Depends on how you interpret the "argument." If the argument is "all software projects can/should 'keep it simple'" then yes, it's clearly a logical fallacy.

But if the argument is "'keep it simple' works for some software projects," one example proves the point. This seems the more generous interpretation.

dvh• 11 years ago

Not to brag but https://github.com/dhewm/dhewm3/blob/master/neo/idlib/Heap.c... (from line 154 down) that seems like another point against using tabs.

nezza-_-• 11 years ago

I always heard "Tabs for indenting, spaces for aligning."

emsy• 11 years ago

Mix tabs and spaces in code and you're in for a fun time :D

jpgvm• 11 years ago

These days just use expand tab, in an age of online code review tools etc it's just better not to have to configure every system to interpret tabs to your given number of spaces - just write the damn spaces into the file.

jordigh• 11 years ago

Yeah, but since every time someone new comes along who doesn't understand what this means (witness the replies you're getting)... no tabs. It's just easier this way.

TorKlingberg• 11 years ago

That works but takes a lot of discipline. More than any team I ever worked with had.

benihana• 11 years ago

I think it's actually a point against lining up variable assignations like that more than a point for spaces (I prefer spaces over tabs btw).

rileyteige• 11 years ago

You think that's bad:

https://github.com/dhewm/dhewm3/blob/master/neo/game/ai/AI.h...

Scroll down and watch the readability disappear.

benhoyt• 11 years ago

Does this fix it? https://github.com/dhewm/dhewm3/blob/master/neo/game/ai/AI.h...

laumars2• 11 years ago

append ?ts=4 to the URL to change GitHubs default 8 character tab to 4 characters wide.

aninteger• 11 years ago

Your comment has nothing to do with the article.. or even keeping things simple.

toxicFork2• 11 years ago

Adding ts=4 fixes it:

https://github.com/dhewm/dhewm3/blob/master/neo/idlib/Heap.c...

(Inspired by https://news.ycombinator.com/item?id=9303351 )

RubyPinch2• 11 years ago

These adverts pretending to be learning experiences, really bother me

"CppDepend Tutorial" would be a better title

huhtenberg• 11 years ago

That's an example of "content marketing".

err4nt2• 11 years ago

You must be the target audience then because I read a great article about Doom3 and have no clue what youre talking about. I also dont know what CppDepend is...

pmelendez4• 11 years ago

I think he refers to the tool the author was using to query the code.

RubyPinch2• 11 years ago

Let's go inside its source code using CppDepend and discover what makes it so special.

And the article is written by the creators of CppDepends

diydsp• 11 years ago

I was seated at the restroom at work yesterday morning when I noticed a strip of plastic had been added to the gap between the metal stall and the metal stall door. It was branded Privacy Cover (patent pending).

Welcome to the future where everything is branded and everyone is an Avon lady, endorsing some set of pet products :)

[a] http://www.rbahelp.com/toilet-partition-privacy-strip-instal... [b] http://www.partitionsandstalls.com/partition-privacy-cover.h... [c] https://www.youtube.com/watch?v=WxWnqR77Dzc&feature=em-uploa...

Rapzid• 11 years ago

You might be interested to know that other parts of the world seem to have solved this quite ingeniously.. At least in Australia and New Zealand it is very common to have stalls with doors hinged and sized so when shut they overlap an outer bit. No gap.

moron4hire• 11 years ago

I didn't realize people peeking through the slim slit was an issue.

corysama• 11 years ago

Ads that are decently educational? Compared to what we deal with currently, I have no problem with edu-ads becoming the next great trend in advertising.

Lawtonfogle• 11 years ago

The issue is that we lose the distinction between content and ad. As this distinction blurs, less people will be able to say which is which. I guess the real question underlying this is the one underlying advertising in general, how much are we morally allowed to manipulate someone who did not give informed consent for the purpose of modifying their behavior in a way that is beneficial to us?

bigbv20932• 11 years ago

As someone who wants to learn modern c++, what are some good resources/books to learn from ? I have python and java experience and I have been reading Accelerated C++ since a while now.

frankzinger2• 11 years ago

Not a definitive list, but these are good:

  The C++ Programming Language, 4th edition
  Bjarne Stroustrup

  The C++ Standard Library, 2nd Edition
  Nicolai M. Josuttis

  Effective C++, More Effective C++, Effective Modern C++ 
  Scott Meyers

  http://en.cppreference.com

pmelendez4• 11 years ago

I would also add Effective STL too.

A Tour of C++ by B. Stroustrup is a good start point for a beginner too

bigbv20932• 11 years ago

Thanks, I'll read through those as well.

replicant• 11 years ago

I resort continuously to this list, https://stackoverflow.com/questions/388242/the-definitive-c-...

zanny• 11 years ago

As an addendum, I highly recommend not reading decade old source code like this as an example of modern C++. C++11/14 have changed the language so much for the better that anything targeting C++03 should be ignored for new projects and especially for new learners.

Also, avoiding Boost and Qt early on is also a good idea. Both have tremendous stylistic and design differences from ISO C++ and while the language supports all of them when using the Boost libraries and Qt toolkit you need to shift mindset entirely in how you are writing code to match the backing architecture. Learn the core language first.

ta0967• 11 years ago

the STL is also totally unlike the standard C library. are things like <algorithm> or <string> to be avoided because the core language is <cstdio>?

frozenport• 11 years ago

I disagree because writing a Qt program is often the end goal.

chadzawistowski2• 11 years ago

I really enjoyed Effective Modern C++. It covered the interesting stuff I wanted to know, and skipped the introductory "in case you've never programmed before" fluff.

http://shop.oreilly.com/product/0636920033707.do

chunkstuntman• 11 years ago

Fabian Sanglard's exploration[1] of Doom3 is much more in depth than this article, though the author does quote Sanglard's analysis albeit with a small source link

[1] http://fabiensanglard.net/doom3_bfg/index.php

pcunite• 11 years ago

Thank you, much better link.

morley• 11 years ago

For what it's worth, that code review is for Doom 3 BFG. This is the review of vanilla Doom 3:

http://fabiensanglard.net/doom3/index.php

The vanilla code review goes into the app structure first, and (what little I've read of) the BFG review compares that codebase against the vanilla one.

EGreg2• 11 years ago

This is back in the good old days when C++ didn't have all the crap, and everyone wanted to stay away from doing advanced stuff with STL and RTTI. Linus famously said that Linux is written in C if only to keep away the C++ developers.

Having said that, I used to write tutorials using the old ways as well: http://flipcode.com/archives/Theory_Practice-Issue_06_Event_...

Does anyone love the new C++, and if so, what are their experiences with being on teams that use the full range of functionality? Do you need a language lawyer?

pmelendez4• 11 years ago

I do enjoy programming in C++11 style. What I like the most is that once you understand the quirks, you would see a lot of opportunities to improve performance but only when necessary (Like using moving semantics if you have to pass a big object through several function calls)

Also STL has improved a lot and I am very happy that I don't need to include a huge dependency such as Boost or POCO just to have a hash table for instance.

Retra4• 11 years ago

This comment represents the my biggest frustration with current programming tools & practices. You shouldn't have to include any libraries. Ever! And you shouldn't have to rewrite some code that does something that's already available and well-written. That, and, if you want to include some functionality, there will be 13,000 versions of the same functionality for you to review before you decide which one to learn and commit to. (And it is easier to write it yourself sometimes.)

There's no reliable way for languages themselves to standardize and aggregate the work that others do. You just hope the language designers are willing to put up a new version, (and that it's a decent one) and they end up doing it ever-so-slowly because it's not automated in any way. Hand-pick and re-roll. There's no metric-based signaling or automated analysis or anything, it's just whatever your experts opine.

joosters2• 11 years ago

I wonder why they opted not to use references? It seems an odd choice to me, did id software give an explanation?

pmelendez4• 11 years ago

I thought exactly the same. Probably they needed to model an empty state and decided that a null pointer was the easier way to do it.

sunir• 11 years ago

The most common argument:

Pass by reference hides the implication of a side effect on the parameter. If you expect the function to manipulate the parameter, passing by pointer is clearer.

Pass by reference was also only added to efficiently support copy constructors and more importantly operator overloading, both of which are syntactic sugar that a C with Classes style would normally avoid.

Template programming also requires pass by reference but templates are sugar on sugar so not the core reason why pass by reference is needed.

Ps. Disclaimer: I haven't checked if the Doom3 code uses these features.

joosters2• 11 years ago

Fair points, although all references should ideally be const unless there are side effects. It's not perfect though, since you can't tell from just viewing the calling code, you have to check the function prototype.

References also help avoid problems with pointer aliasing, and make it clear that the called function definitely cannot delete the passed objects. So it's more than just syntactic sugar.

(n.b. I'm not arguing that pointers are bad and should never be used, I still just don't see a clear reason never to use references. The id Software coders are smart, they must have had good reason to pick their choice)

krallja• 11 years ago

Probably because Carmack didn't actually know C++[1], and C doesn't support references.

1: https://news.ycombinator.com/item?id=9303387

Toine2• 11 years ago

https://github.com/dhewm/dhewm3/blob/master/neo/game/Target....

This is the "nicest looking code [you] have ever seen" ?

toxicFork2• 11 years ago

What's wrong with this?

golergka3• 11 years ago

Over 150 lines of code in a simple method?

C-style declaration of all the variables in the beginning? (Yes, I know what Carmack said about how he written the project; this explains it, but doesn't make it good C++ code.)

Unclear flow with just one comment, which doesn't really explain anything?

edc117• 11 years ago

Just curious, are you cherry picking, or are there legitimately many areas of the code like this? I haven't had a chance to look yet.

Toine2• 11 years ago

To be honest i didn't look at all the code, but yes there are many areas like this.

dman2• 11 years ago

Any critiques in specific?

CamperBob2• 11 years ago

   if ( ent->GetRenderEntity()->gui[ j ] && 
   ent->spawnArgs.FindKey( j == 0 ? "gui_demonic" : va( 
   "gui_demonic%d", j+1 ) ) ) { ent->GetRenderEntity()->gui[ 
   j ] = uiManager->FindGui( ent->spawnArgs.GetString( j == 0 
   ? "gui_demonic" : va( "gui_demonic%d", j+1 ) ), true );

Really?

w23j• 11 years ago

This comment by Carmack seems to imply that the restrained use of advanced C++ features was more by accident then by design:

I had C and Objective-C background, and I sort of "slid into C++" by just looking at the code that the C++ guys were writing. In hindsight, I wish I had budgeted the time to thoroughly research and explore the language before just starting to use it.

You may still be able to tell that the renderer code was largely developed in C, then sort of skinned into C++.

(Source: http://fabiensanglard.net/doom3/interviews.php)

xamuel• 11 years ago

That doesn't necessarily imply that he's saying he should've used more advanced features. It could just as well mean he should've understood better the features he did use.

scott_s2• 11 years ago

Agreed - but the post implies all of the choices made were mindful choices. Carmack indicates that is not necessarily so.

Nilzor• 11 years ago

No one have issues with source code files 5100 lines long? https://github.com/dhewm/dhewm3/blob/master/neo/game/ai/AI.c...

Someone1234• 11 years ago

You make it sound like it is a single 5100 line long method. It seems actually very well organised in that file.

If you're using any kind of IDE then this wouldn't bug you as you can just jump to the point in the file you need.

clarry• 11 years ago

And if you're not using a fancy IDE, jumping around in one file can be much easier than jumping around a dozen files.

chrisseaton• 11 years ago

Demonstrably, 5100 line long files are no barrier to quality software.

highCs• 11 years ago

The game was a commercial success for id Software; with more than 3.5 million copies of the game were sold.

Wrong/Cheated. It was such a success that they had to sell the company - they sold ID-Software...

golergka3• 11 years ago

Why are you referring to the process of selling the company as an opposite of financial success?

ksk• 11 years ago

I can't say for Id Software, because I have no clue about their financials. But historically, people who run profitable companies do not want to sell them. They want to grow them so they can make even more money. These days startups which are "owned" by VC money, usually have to sell so the VCs can recover their investment.

talmand2• 11 years ago

Doom 3 - 2004

ZeniMax - 2009

It seemed to do well enough to slow the need to sale for five years or so.

Or maybe, just maybe, it was so successful of a company that another company bought it to share in the success.

Scuds• 11 years ago

They were building Rage at the time. I'm sure the budget for that game was like 5x that of D3. Shit runs late, cost blooms. Lots of 90's era twenty person shops had trouble dealing with increasing costs.

stefantalpalaru• 11 years ago

Note: Please offer only positive, constructive comments - we are looking to promote a positive atmosphere where collaboration is valued above all else.

And keep your rose-colored glasses on at all times. You shall see no evil, hear no evil, speak no evil and never grow out of childhood.

frik• 11 years ago

Doom3 is the proof that “keep it simple” works

This statement suits even better to id Tech 3 (Quake 3). John Carmack mentioned: I still think the Quake 3 code is cleaner, as a final evolution of my C style, rather than the first iteration of my C++ style [Doom 3]: http://kotaku.com/thanks-a-few-comments-in-some-ways-i-still... and he linked to his blog post about "Functional Programming in C++" on the now defunct but former popular AltDevBlog: https://web.archive.org/web/20130126164111/http://www.altdev...

The engine of Doom 3 (id Tech 4) was good. The game itself was repetitive and a bit boring. It was a few months late Aug 2004, and Far Cry 1 (March 2004) already overshadowed it in terms of graphics and gameplay.

Licensing the id-Engine to other companies was very successful during the id Tech 2 (Quake 1/2) and id Tech 3 (Quake 3) era. Back then the Unreal engine was only used in Unreal and Unreal Tournament '99, with Deus Ex as an early adopter.

But few games were released starting with id Tech 4 (Doom 3) and later id Tech 5 (Rage). Compromises during the development of id Tech 4+ meant it wasn't suitable for many different purposes. Only small levels with a few light sources were possible - the later "mega texture" addition partly solved that issue but meant a huge hardware step during development and prevented Mods and custom maps. In retrospect the Unreal 3+ and CryEngine 1+ offered comparable results without sacrifice their universalizability. http://en.wikipedia.org/wiki/Far_Cry_(video_game) , http://en.wikipedia.org/wiki/Doom_3 , http://en.wikipedia.org/wiki/Id_Tech_4

The Call of Duty franchise is still using modified Quake 3 engine heavily extended with Ritual's ÜberTools, now named IW engine and comes with many modern features like texture streaming. Half Life 1+2 are based on a heavily modified Quake 1 engine. http://en.wikipedia.org/wiki/Quake_engine , http://upload.wikimedia.org/wikipedia/commons/6/63/Quake_-_f... , http://en.wikipedia.org/wiki/File:Quake_-_family_tree_2.svg , http://en.wikipedia.org/wiki/Heavy_Metal:_F.A.K.K.%C2%B2

All of these id tech engine games can be edited with the GtkRadiant map editor (Half Life, Call of Duty, Quake 3, Doom 3, etc.): http://en.wikipedia.org/wiki/GtkRadiant

scott_s2• 11 years ago

I was surprised to learn that CoD still uses something based on the Quake 3 engine. Any idea how much the engine has changed?

Crito3• 11 years ago

Yeah, in particular I'd be interested to know if CoD still uses Quake 3's VM model.

amyjess2• 11 years ago

Wait, HL2 uses the Quake engine? I know HL1 did, but I thought HL2's engine was Valve's in-house work.

chadzawistowski2• 11 years ago

HL1 uses the GoldSrc engine, which is a heavily-modified version of the Quake engine.

GoldSrc was again heavily modified to become the Source engine, but it does retain direct lineage to Quake.

http://en.wikipedia.org/wiki/Source_%28game_engine%29#Origin...

topkekz• 11 years ago

http://kotaku.com/5975610/the-exceptional-beauty-of-doom-3s-...

Reply from Carmack himself: http://kotaku.com/thanks-a-few-comments-in-some-ways-i-still...

melling• 11 years ago

Lots of structs is how http://handmadehero.org is being built.

"As we can observe many structs are defined, for example more than 40% of DoomDLL types are structs. They are systematically used to define the data model. This practice is adopted by many projects, this approach has a big drawback in case of multithreaded applications. Indeed, structs with public fields are not immutable."

mahouse• 11 years ago

What's the IDE he uses?

Narishma• 11 years ago

Visual Studio, like most game developers.

CyberDildonics2• 11 years ago

I wonder what John Camack's current thoughts are on C++ design. I rarely use inheritance and usually have either inlined functions or functions that operate on arrays or many objects at a time. I also use templates when they deal with straight type substitution (including functions). I am though starting to get familiar with extern templates to be able keep compile times down.

CyberDildonics2• 11 years ago

If anyone wants to see the opposite of keep it simple, take a look at the source for the build engine. It will blow your mind.

Doom3 is the proof that “keep it simple” works

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