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Dev Diary: John Carmack on RAGE for iOS

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Re: Dev Diary: John Carmack on RAGE for iOS

#31

Post by sandGorgon »

pkaler wrote: post #3

I had been harboring some suspicions that our big codebases might benefit from the application of some more of the various “modern” C++ design patterns, despite seeing other large game codebases suffer under them. I have since recanted that suspicion. Quoted for truth. I learned C++ during the Meyers/Sutter era. Then Andrei Alexandrescu came along and I had Boost libraries sprinkled all over my code. My beard is grow…

Do you use STL then ? Because, that was pretty much the only reason I started using C++.

Or do you write your own containers

Re: Dev Diary: John Carmack on RAGE for iOS

#32

Post by InclinedPlane »

cosbynator wrote: post #6
colkassad wrote: post #5

Earlier quoted context omitted.

I found this part of his article to be interesting. I'm working through a CS degree and learning C++ for the first time after cutting my teeth on Python and C#. What exactly does he mean by "(restrained) C++"? He mentions a contract studio using the STL and boost. We are using the STL in our data structures class...does John Carmack eschew the STL and roll his own data structures?

In his own words: http://twitter.com/#!/ID_AA_Carmack/status/21119808432 I consider myself a decent programmer but I have more trouble reading template heavy C++ than I do haskell code. To me, restrained C++ means keeping the unreadable bits outside the code base and isolated in their own library, like Boost :)

Template meta programming is very neat stuff, but the problem is that it's basically another language that lives on top of your language. Except that it's not a full-fledged language so it lacks all of the features that keep other programming languages manageable. It's like assembly code, except instead of just twiddling some bits in registers and RAM you're working with a far more complicated entity (an entire program), making the problem that much worse.

Re: Dev Diary: John Carmack on RAGE for iOS

#33

Post by InclinedPlane »

WesleyJohnson wrote: post #22
zmonkeyz wrote: post #20

John Carmack has always been my mancrush since the Quake days.

I consider myself sharp, but not smart. So I'm often humbled when I read stuff on Hacker News, but I am always completely dumbfounded when I read any of the technical pieces by John Carmack. I read 90% of that article and I comprehended about 20% of it. I toil with silly web development side projects for months on end that evolve into nothing and he's coding complete games, single-handedly (though admittedly using so…

You know he builds rockets in his spare time right? http://www.armadilloaerospace.com/

Re: Dev Diary: John Carmack on RAGE for iOS

#34

Post by palish »

dhess wrote: post #29
pkaler wrote: post #24

Earlier quoted context omitted.

Throwing an exception is a misnomer. An exception doesn't necessarily mean that an error happened. It means, "please unwind the call stack". Unwinding the call stack in a game is a no-no. Games, especially the simulation, must be deterministic. An exception would most likely destroy determinism. The simulation/AI is a big, hairy, ugly set of if/else and switch statements anyway. Adding extra error checking is not an…

> Unwinding the call stack in a game is a no-no. For the most part, I agree, which is why I said they're probably only appropriate in games when used judiciously, e.g., for fatal errors.

Exceptions are actually nice for single methods, even in a game.

  void    Horse::ImOnA()
  {
    try
    {
       Giddyup();

       if (IsDead())
         EX_ERROR("Guess I wasn't on it.");

       if (IsFlippingTheFuckOut())
         EX_WARN("Safety hazard!  Get the f outta the way!");
  
       Feed();
    }
    catch (CException& ex)
    {
      ex.Process("Horse::ImOnA() - ", NO_THROW);
    }
    CleanupAfterHorse();
  }
If the horse is dead, then "Horse::ImOnA() - Guess I wasn't on it." will be printed to the console.

If the horse is acting like my mother, then "Horse::ImOnA() - Safety hazard! Get the f outta the way!" will be printed to the console.

Etc.

So this is a nice way to report errors. It's basically a typed goto. But don't you dare try to use it for flow control! >:(

You can report various "levels": EX_DEBUG, EX_WARN, EX_ERROR, EX_FATAL

ex.Process() checks what kind of exception it is. And for EX_FATAL, for example, it will terminate the application (after writing the message to a log file).

It's quite nice to use exceptions in this way, because you rarely ever need to even think about making your methods "exception safe" at all.

Re: Dev Diary: John Carmack on RAGE for iOS

#35

Post by palish »

badmonkey0001 wrote: post #27
wmf wrote: post #4

Earlier quoted context omitted.

You can thank ESRB for that.

Speaking of ESRB ratings, how is this going to get on the iOs devices? Aren't the app store rules against the following: "This is the perfect setup for a quintessential first person shooter game play experience — you pick your targets, aim your shots, time your reloads, dodge the bad guys, and try and make it through to the end of the level with a better score than last time. Beyond basic survival, there are pickups,…

Oh come on... Here are the specific guidelines you are referring to:

Apps portraying realistic images of people or animals being killed or maimed, shot, stabbed, tortured or injured will be rejected

Apps that depict violence or abuse of children will be rejected

"Enemies" within the context of a game cannot solely target a specific race, culture, a real government or corporation, or any other real entity

Apps involving realistic depictions of weapons in such a way as to encourage illegal or reckless use of such weapons will be rejected

Apps that include games of Russian roulette will be rejected

How would those guidelines apply to someone's awesome first person shooter?

Maybe the "reckless use of weapons" part. But that's not the spirit of the law --- the spirit was likely to prevent people from e.g. making an app that gives a step-by-step photographic guide to creating a pipe bomb, or something of that sort.

Re: Dev Diary: John Carmack on RAGE for iOS

#36

Post by acqq »

dhess wrote: post #17
pkaler wrote: post #3

I had been harboring some suspicions that our big codebases might benefit from the application of some more of the various “modern” C++ design patterns, despite seeing other large game codebases suffer under them. I have since recanted that suspicion. Quoted for truth. I learned C++ during the Meyers/Sutter era. Then Andrei Alexandrescu came along and I had Boost libraries sprinkled all over my code. My beard is grow…

I'm on the same arc (especially the template Kool-Aid phase), except perhaps further along: now I forgo C++ entirely and write plain C because it's so much easier to wrap from higher-level languages. I do miss smart pointers, but on the other hand, dealing with malloc and friends keeps me honest about what really needs to be written in C.

For the high performance stuff I write my kind of restrained C++: never STL in the interfaces of the "modules," use STL algorithms (they are good) but otherwise manage memory in custom ways (which is easier by not using STL containers!).

But I had to solve one interesting problem using some recursive definitions and code, and discovered that once I "freed" the code from classes (made them C functions) I was able to express it properly -- just having them as members prevented me to see that the solution is much more obvious when you actually use plain pointers and don't think about the same "object" even during the life of the function. Add to that in the member "this" can't be null.

When you need real expressiveness, C can't be beaten. C++ syntactic sugar helps sometimes, but limiting to it is... limiting!

Re: Dev Diary: John Carmack on RAGE for iOS

#37

Post by omnigoat »

dhess wrote: post #28
omnigoat wrote: post #25

Earlier quoted context omitted.

You're making two mistakes: One about how exceptions work, and another by not considering our constraints. Exceptions don't just add an overhead when they're thrown, they add overhead for every function call. How else would the exception-handling runtime know to unwind the stack to the correct addresses? It is this performance degradation that we avoid. Why? For the PC, it doesn't really matter. The XBox360 doesn't h…

> Exceptions don't just add an overhead when they're thrown, they add overhead for every function call. How else would the exception-handling runtime know to unwind the stack to the correct addresses? With unwind descriptors/exception handling tables, which can be stored in a read-only segment of the executable and don't need to be paged in until an exception occurs. They have no runtime performance cost until an exc…

Yes, that's fair for the PC (I was aware of this for the PC, which is why I said exceptions don't really matter on the PC). But (from memory) I don't believe the Xbox allows for this, even though it uses a very similar variant of the same compiler. It's a moot point, though, for all the other reasons I mentioned. When you've got a cross-platform codebase - and there are precious few platform-exclusive codebases these days - it is far easier to turn exceptions off across the board than deal with individual platform's quirks.

Re: Dev Diary: John Carmack on RAGE for iOS

#38

Post by NickPollard »

WesleyJohnson wrote: post #22
zmonkeyz wrote: post #20

John Carmack has always been my mancrush since the Quake days.

I consider myself sharp, but not smart. So I'm often humbled when I read stuff on Hacker News, but I am always completely dumbfounded when I read any of the technical pieces by John Carmack. I read 90% of that article and I comprehended about 20% of it. I toil with silly web development side projects for months on end that evolve into nothing and he's coding complete games, single-handedly (though admittedly using so…

I'm a game developer (though only ~3 years experience) and I only understood 50% of it. Gives me something to aspire to that someone can be that good at it.

Re: Dev Diary: John Carmack on RAGE for iOS

#39

Post by petercooper »

NickPollard wrote: post #38
WesleyJohnson wrote: post #22

Earlier quoted context omitted.

I consider myself sharp, but not smart. So I'm often humbled when I read stuff on Hacker News, but I am always completely dumbfounded when I read any of the technical pieces by John Carmack. I read 90% of that article and I comprehended about 20% of it. I toil with silly web development side projects for months on end that evolve into nothing and he's coding complete games, single-handedly (though admittedly using so…

I'm a game developer (though only ~3 years experience) and I only understood 50% of it. Gives me something to aspire to that someone can be that good at it.

I'm not even a game developer or a C++ developer but he gives me the same motivation. It blows my mind there's a guy who clearly has a significant level of wealth (healthy 8 digits, at least) yet gets down into the guts of coding an iPhone game for months at a time. That's world champion passion right there.
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