Our DNA is written in Swift

Cracker Tracker and Apple Stalker

I would like to draw your attention to two ideas that might work if enough people organize and contribute. I know that your time is valuable and most of you won’t have extra time to spend helping with a “good iPhone cause”, but hear me out. If we organize, contribute automatically we can all benefit enormously.

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Variable Number of Decimal Places

Trapper asks:

I have one integer holding a variable number of decimal places that another variable needs to be rounded to when I stringWithFormat it. What is the correct way to do this?

Trapper is not content with just specifying %.2f in a stringWithFormat, but he wants the number of decimal places to be dependent on a second variable.

Here is the shortest method I came up with.

int decimals = 3;
double d = 3.1415;
NSString *format = [NSString stringWithFormat:@"%%%0.1ff", decimals/10.0];
NSString *formattedString = [NSString stringWithFormat:format, d]; // e.g. %0.3f 

I got confused at first because the NSLog would always output a strange value when wanted to output the formatting string. Then I remembered that the first parameter of NSLog itself is also interpreting formatting information. NSLog combines stringWithFormat into the output.

That’s good to know in case you want to add an NSLog statement for debugging floating point variables.

double d = 3.1415;
NSLog("%0.2f", d);  // formatting directly here

Don't Quit Your Day Job

Rob asks:

I have decided to start writing apps as a full time job. Assuming I can master this, and assuming I can get 1 app per month accepted in the App Store, can anyone give me some guidance on how much income I am likely to make.

Here are some numbers from my data that might help you:

  • A general purpose tool app like GeoCorder might sell between 1 and 5 copies a day.
  • Something interesting or unusual like iFR Cockpit can expect to sell around 5-10 copies a day.
  • A niche market tool like iWoman might to do well at 10-20 copies a day.
  • A game like LuckyWheel would sell around 20 copies a day IF you also have a LITE Version that has about 900-1000 downloads a day. Without a LITE version it could only be 5-10 copies a day.;-)

So assuming you concentrate on niche apps and games and calculating from $25 a day per such app you might make around $2000 a month if you manage to land 3 of those in the store. NOT taken into account additional cost like taxes or hardware. And not considering that Apple has the painful final word. Does that sound easy enough for you to immediately quit your day job?

For me it didn’t and it took me 8 months to get where I am today. It’s ok to see it as a lucrative hobby or even second income, but to stake your existance solely iPhone development you have to be extremely disciplined. Or even better: to know how to build teams of bright minds who can bring skills to the table that your don’t possess yourself.

Anything goes … into NSArray

When switching to or beginning with Objective C you might be tempted to try to use the old c-style arrays, but that’s better left to the hard core C-enthusiasts. For programming Cocoa Touch we always use the NSArray class because of the additional intelligence it provides for us, not to mention integration with memory management.

The first thing I ever added into NSArray was string objects. And so will probably everybody who starts with Objective C.

NSString *someText = @"Static Text";  // static allocation
NSString *someMoreText = [[NSString alloc] initWithString:@"More Static Text"]; // manually allocated
NSArray *myArray = [NSArray arrayWithObjects:someText, someMoreText, nil];  // note the nil
[someMoreText release];  // don't forget to release
NSString *retrievedText = [myArray objectAtIndex:1]; // first index = 0

How about numbers? Generally you can only add instances of objects into NSArray. But luckily Apple has created the NSNumber class which provides a container object for any kind of number, i.e. int, float or even BOOL.

int i=123;
float f=5.0;
NSNumber *num_i = [NSNumber numberWithInt:i];
NSNumber *num_f = [NSNumber numberWithFloat:f];
NSNumber *num_b = [NSNumber numberWithBool:YES];
NSArray *myArray = [NSArray arrayWithObjects:num_i, num_f, num_b, nil];

With the methods above you are able to add strings and numbers into arrays. There is yet another wrapper class that allows to put even more complex data types and structs into arrays: NSValue. Most usefully are the UIKit additions to NSValue which give you the possibility of packaging CGRect, CGPoint, CGAffineTransform or CGSize structs into objects. And those are just as easy to put into an array.

CGRect aRect = CGRectMake(0, 0, 100.0, 100.0);
CGSize aSize = CGSizeMake(10.0, 20.0);
NSValue *val_rect = [NSValue valueWithCGRect:aRect];
NSValue *val_size = [NSValue valueWithCGSize:aSize];
NSArray *myArray = [NSArray arrayWithObjects:val_rect, val_size, nil];

Soon you will find it odd that NSArray does not have any method to add and remove objects. The reason for this is that most standard objects are non-changable (aka “immutable”) as such. To gain such modification features you have to use the mutable cousin NSMutableArray. This gives you methods like addObject or removeObject.

NSMutableArray *myArray = [[NSMutableArray alloc] init];
[myArray addObject:@"first string"];
[myArray addObject:@"second string"];
[myArray addObject:@"third string"];
[myArray removeObjectAtIndex:1];
NSLog([myArray description]);  // a quick way to show contents
[myArray release];

NSArrays are the meat and bones of most Objective-C apps. Anybody trying to master this language has no way around them.

LuckyWheel 1.0.3

Since we released LuckyWheel 1.0.2 together with a Lite Version we have around 1000 new downloads every day. Of course we are listening to all the user feedback und therefore I am hastily pushing out a new update. This is mostly aimed at the many Italian users, but one change will also benefit Spanish and French players.

  • Italian UI and Instructions added
  • accented letters are now counted as guessed correctly if you guess the non-accented letter. i.e. E = È
  • completely replaced Italian proverbs with cleaned up set
  • prettier icon

Depending on how long Apple takes to check it out I guess you will see the update appear in about one week.

Apple Rejects Incredibly Useful iTunes Report App

ASiST First screenshotMostly out of personal necessity I had created MyAppSales to download and chart the sales reports available on iTunes Connect, the website where Apple makes daily reports available for only 7 days. A dozen BETA testers helped me improve it and iron out some kinks and finally it was ready to be submitted for sale on the app store.

Some people suggested that Apple might not want any app to interface with their website, but someone found an all called Sales Report on the app store for $14.99 which does precisely that. I assumed that Apple had to be fair and allow all apps that do the same thing. So I submitted it.

There was an occasional back and forth where every time I got an additional line of the full answer, but I kept arguing for fairness. After many weeks of keeping my app MyAppSales under review they finally came back with a rejection reason that I cannot counter:

Thank you for submitting your application to the App Store. Unfortunately, your application My App Sales cannot be added to the App Store because it violates section 3.3.7 of the iPhone SDK Agreement:

“Applications may not use any robot, spider, site search or other retrieval application or device to scrape, retrieve or index services provided by Apple or its licensors, or to collect information about users for any unauthorized purpose. ”

There is no public API allowing information from iTunes Connect to be used in the manner demonstrated by your application. 

Now I am baffled. I and a dozen other people keep using MyAppSales and we are quite happy with it. But Apple seemingly does not feel a moral obligation to appliy those pesky SDK Laws equally to all developers.

Requests for comment about why the other app is still available on the app store have not been answered so far. I sent an e-mail to “Maringo Holdings, LLC” to congratulate them for having successfully outsmarted Apple.

Currently I have no time or strength to rip out the heart and usefulness from my app. Therefore for now I am offering the source code for purchase. You can compile the app yourself and use it on all your iPhones as you please. I think $15 is a fair price. Send it to me via PayPal ( and I will send you the source project. I will also keep providing free updates to source license holders.

Maybe in the future I will find a workaround, either via an FTP server in between Apple and the App or maybe interface with one of those numerous services that are popping up proposing to manage your reports online.

SSD Impressions: I’m Supercharged!

Lately we saw prices for SSDs beginning to drop because of increased competition between manufacturers of RAM chip based products. Once a colleague of mine showed off his mid-2008 MacBook running on an SSD my envy-bone was tickled.

Doing due diligence I found a couple of sites advertising lower prices, but only Amzon actually had the OCZ APEX 120GB in stock. So I headed over to to purchase one. Actually I went to the German site, where I shelled out 370 Euros, users in the US have to pay even less. So the OCZ APEX currently blows the competition out of the water in terms of price/performance.

Before installing I used XBench to gather a few stats on the original HDD in my mid-2008 MacBook Pro. Also I timed a couple of other usual tasks to have a basis for comparison. What good is having an impressive machine if nobody knows about how great it is? 😉

At first I was enthusiastic to install it myself but without the proper tools I was not able to remove the final bracket holding down the drive. Over night my charger died and I feared the worst because I was no longer able to boot my MBP with empty battery. So I took it all to an authorized Apple Support Center in Vienna, asking for a repair and while they where at it, to also install the SSD. With the Guide at iFixIt anybody can make the upgrade themselves, provided they get the necessary tools in advance.

I had to pay a full hour work plus 50% extra for express service, the charger exchanged for a new one for free. But at least I got my MBP back the same day, SSD installed and a basic Leopard 10.5.6 on it. It took me a while to copy back all files and settings from the SuperDuper image I had created the day before, but the next day I was ready to evaluate the performance difference.

The OCZ APEX model has an internal RAID 0 with two chips working as one which effectively doubles the throughput which goes over the SATA 2 interface. This is compatible with the SATA 1 in my MBP, which rates at 1.5 Gigabits, or about 150 theoretical Megabytes per second. OCZ claims a read rate of up to 260 MB/s and up to 160 MB/s for writing for the APEX series. This is why I chose it because I wanted to max out both the reading and writing throughput possible over SATA 1 at the lowest possible price for 120 GB.

So much for marketing, here come the real life results:


All of the numbers speak rather clearly. On average it is fair to say that the SSD is four times as fast. But even more impressive than benchmark numbers is how much faster those many standard tasks become. This is what you actually notice.


Most of the time of the booting process is unrelated to the performance of the harddisk but is spent checking the RAM, loading the EFI etc. Once the turning wheel appears it is only a few seconds before the desktop is visible and fully active. Shutdown is most impressive, but who really shuts down his Mac anyway? MacBooks are the only laptops I know where you can close the lid to standby and open it to immediately continue working.

Opening apps generally is three times as fast, building times with XCode are effectively halfed.

The other side effects of coding on an SSD-based MacBook Pro are almost as obvious:

  • Shock Resistance. If you smash your MacBook to pieces (up to 1500G) the data on the SSD will still be intact. This goes hand-in-hand with the next point.
  • Data Safety. You eliminate a single point of failure from your development system as head crashes are still the worst total failure possible. And they do happen. How valuable is the code you write while on the road without being able to back it up?
  • Power Consumption. Reduced. Maybe. Slightly. A few minutes.
  • Noise. There is no clicking to hear if you put your ear on your top case. You now have to rely on the fans to know that your MBP is still alive and has not become an undead vampire.
  • Less time spent waiting. If you consider all those reduced waiting times for the multitude of small tasks involved in created an app, all those Seconds will add up to days until the end of your life.
  • Bling Bling. If you happen to mention that you have changed to SSD most people will either think you are rich or the Uber-Geek.

If only I could get my hands bionically enhanced then this would also tripple the amount of code I can write while sitting on the train. But until I do I have to be content with the advantages outlined above.

Was that you that I just overtook in cyberspace? 😉

Exercise: Compile Wolfenstein 3D for iPhone

If you are around my age then the first 3D Shooter you have played might have been Wolfenstein 3D. Still unforgotten and causing a smile are the words “Ahhh, mein Leben!” shouted by German soldiers expiring.

John Carmack, coding god and founder of ID software has spent some time on creating an iPhone conversion and graciously provides the source code for it on ID’s FTP server.

If you download it and dig through the ZIP file you will find a letter from John and a read me explaining that the iPhone code is found in wolf3d/newCode/iphone. Browse there and open the wolf3d.xproj file to open the project in XCode.

If you just hit Build&Go you get two error messages where two symbols cannot be resolved by the linker. There is a workaround on with which you can compile and run Wolf3D on the iPhone Simulator.

If you switch to iPhone as target platform you get the usual message that the currently set certificate cannot be found for code signing.


Code Signing Identity ‘iPhone Developer: Cass Everitt’ does not match any code-signing certificate in your keychain.


This is easy to fix. Simply replace the mentioned signing identity with your own development identity. This is in the info of target wolf3d.

After this you are good to go. The app installs on your development iPhone and runs very well. At first I thought that sound was missing, but that was because my ringer switch was off. 😉

Wolfenstein 3D on iPhone

Next I’ll insert my own “Mein iPhone!” sound effect for a more modern touch. 😉

John Carmack's iPhone Letter

Contained within the ZIP file with the “Wolfenstein 3D” source code is this lengthy but very interesting letter by gaming god John Carmack.

iPhone development*

By John Carmack, Technical Director, Id Software


I had been frustrated for over a year with the fact that we didn’t have any iPhone development projects going internally at Id.  I love my iPhone, and I think the App Store is an extremely important model for the software business.  Unfortunately, things have conspired against us being out early on the platform.


Robert Duffy and I spent a week early on starting to bring up the Orcs & Elves DS codebase on the iPhone, which would have been a nice project for a launch title, but it wasn’t going to be a slam dunk.  The iPhone graphics hardware is a more capable superset of the DS hardware (the driver overhead is far, far worse, though), but the codebase was fairly DS specific, with lots of Nintendo API calls all over the place.  I got the basics drawing by converting things to OpenGL ES, but I was still on the fence as to whether the best approach to get all the picky little special effects working would be a complete GL conversion, or a DS graphics library emulation layer.  Coupled with the fact that the entire user interface would need to be re-thought and re-tested, it was clear that the project would take several months of development time, and need artists and designers as well as coding work.  I made the pitch that this would still be a good plan, but the idMobile team was already committed to the Wolfenstein RPG project for conventional Java and BREW mobile phones, and Anna didn’t want to slip a scheduled milestone on the established, successful development directions there for a speculative iPhone project.


After thinking about the platform’s capabilities a bit more, I had a plan for an aggressive, iPhone specific project that we actually started putting some internal resources on, but the programmer tasked with it didn’t work out and was let go.  In an odd coincidence, an outside development team came to us with a proposal for a similar project on the Wii, and we decided to have them work on the iPhone project with us instead.  We should be announcing this project soon, and it is cool.  It is also late, but that’s software development…


Late last year, the mobile team had finished up all the planned versions of Wolfenstein RPG, but EA had suggested that in addition to the hundreds of customized versions they normally produce for all the various mobile phones, they were interested in having another team do a significant media quality improvement on it for the iPhone.  While Wolf RPG is a very finely crafted product for traditional cell phones, it wasn’t designed for the iPhone’s interface or capabilities, so it wouldn’t be an ideal project, but it should still be worth doing.  When we got the first build to test, I was pleased with how the high res artwork looked, but I was appalled at how slow it ran.  It felt like one of the mid range java versions, not better than the high end BREW as I expected.  I started to get a sinking feeling.  I searched around in the level for a view that would confirm my suspicion, and when I found a clear enough view of some angled geometry I saw the tell-tale mid-polygon affine swim in the texture as I rotated.  They were using the software rasterizer on the iPhone.  I patted myself on the back a bit for the fact that the combination of my updated mobile renderer, the intelligent level design / restricted movement, and the hi-res artwork made the software renderer almost visually indistinguishable from a hardware renderer, but I was very unhappy about the implementation.


I told EA that we were NOT going to ship that as the first Id Software product on the iPhone.  Using the iPhone’s hardware 3D acceleration was a requirement, and it should be easy — when I did the second generation mobile renderer (written originally in java) it was layered on top of a class I named TinyGL that did the transform / clip / rasterize operations fairly close to OpenGL semantics, but in fixed point and with both horizontal and vertical rasterization options for perspective correction.  The developers came back and said it would take two months and exceed their budget.


Rather than having a big confrontation over the issue, I told them to just send the project to me and I would do it myself.  Cass Everitt had been doing some personal work on the iPhone, so he helped me get everything set up for local iPhone development here, which is a lot more tortuous than you would expect from an Apple product.  As usual, my off the cuff estimate of “Two days!” was optimistic, but I did get it done in four, and the game is definitely more pleasant at 8x the frame rate. 

And I had fun doing it.


Since we now were doing something resembling “real work” on the iPhone at the office, we kept it going at a low priority.  One of the projects Cass was tinkering around with at home was a port of Quake 3, and we talked about different interface strategies every now and then. 

Unfortunately, when we sat down to try a few things out, we found that

Q3 wasn’t really running fast enough to make good judgments on iPhone control systems.  The hardware should be capable enough, but it will take some architectural changes to the rendering code to get the most out of it.


I was just starting to set up a framework to significantly revise Q3 when I considered the possibility of just going to an earlier codebase to experiment with initially.  If we wanted to factor performance out of the equation, we could go all the way back to Wolfenstein 3D, the grandfather of FPS games.  It had the basic run and gun play that has been built on for fifteen years, but it originally ran on 286 computers, so it should be pretty trivial to hold a good framerate on the iPhone.


Wolfenstein was originally written in Borland C and TASM for DOS, but I had open sourced the code long ago, and there were several projects that had updated the original code to work on OpenGL and modern operating systems.  After a little looking around, I found Wolf3D Redux at  One of the development comments about “removal of the gangrenous 16 bit code” made me smile.


It was nice and simple to download, extract data from a commercial copy of Wolfenstein, and start playing on a PC at high resolution.  Things weren’t as smooth as they should be at first, but two little changes made a huge difference — going at VBL synced update rates with one tic per cycle instead of counting milliseconds to match 70 hz game tics, and fixing a bug with premature integralization in the angle update code that caused mouse movement to be notchier than it should be.  The game was still fun to play after all these years, and I began to think that it might be worthwhile to actually make a product out of Wolfenstein on the iPhone, rather than just using it as a testbed, assuming the controls worked out as fun to play.  The simple episodic nature of the game would make it easy to split up into a $0.99 version with just the first episode, a more expensive version with all sixty levels, and we could release Spear of Destiny if there was additional demand.  I was getting a little ahead of myself without a fun-to-play demonstration of feasibility on the iPhone, but the idea of moving the entire line of classic Id titles over — Wolf, Doom, Quake, Quake 2, and Quake Arena, was starting to sound like a real good idea.


I sent an email to the Wolf 3D Redux project maintainer to see if he might be interested in working on an iPhone project with us, but it had been over a year since the last update, and he must have moved on to other things.  I thought about it a bit, and decided that I would go ahead and do the project myself.  The “big projects” at Id are always top priority, but the systems programming work in Rage is largely completed, and the team hasn’t been gated on me for anything in a while.  There is going to be memory and framerate optimization  work going on until it ships, but I decided that I could spend a couple weeks away from Rage to work on the iPhone exclusively.  Cass continued to help with iPhone system issues, I drafted Eric Will to create the few new art assets, and Christian Antkow did the audio work, but this was the first time I had taken full responsibility for an entire product in a very long time.


*Design notes*


The big question was how “classic” should we leave the game?  I have bought various incarnations of Super Mario Bros on at least four Nintendo platforms, so I think there is something to be said for the classics, but there were so many options for improvement.  The walls and sprites in the game were originally all 64 x 64 x 8 bit color, and the sound effects were either 8khz / 8 bit mono or (sometimes truly awful) FM synth sounds.  Changing these would be trivial from a coding standpoint.  In the end, I decided to leave the game media pretty much unchanged, but tweak the game play a little bit, and build a new user framework around the core play experience.  This decision was made a lot easier by the fact that we were right around the 10 meg over-the-air app download limit with the converted media.  This would probably be the only Id project to ever be within hailing distance of that mark, so we should try to fit it in.


The original in-game status bar display had to go, because the user’s thumbs were expected to cover much of that area.  We could have gone with just floating stats, but I thought that BJ’s face added a lot of personality to the game, so I wanted to leave that in the middle of the screen.  Unfortunately, the way the weapon graphics were drawn, especially the knife, caused issues if they were just drawn above the existing face graphics.  I had a wider background created for the face, and used the extra space for directional damage indicators, which was a nice improvement in the gameplay.  It was a tough decision to stop there on damage feedback, because a lot of little things with view roll kicks, shaped screen blends, and even double vision or blurring effects, are all pretty easy to add and quite effective, but getting farther away from “classic”.


I started out with an explicit “open door” button like the original game, but I quickly decided to just make that automatic.  Wolf and Doom had explicit “use” buttons, but we did away with them on Quake with contact or proximity activation on everything.  Modern games have generally brought explicit activation back by situationally overriding attack, but hunting for push walls in Wolf by shooting every tile wouldn’t work out.  There were some combat tactics involving explicitly shutting doors that are gone with automatic-use, and some secret push walls are trivially found when you pick up an item in front of them now, but this was definitely the right decision.


You could switch weapons in Wolf, but almost nobody actually did, except for occasionally conserving ammo with the chain gun, or challenges like “beat the game with only the knife”.  That functionality didn’t justify the interface clutter.


The concept of “lives” was still in wolf, with 1-ups and extras at certain scores.  We ditched that in Doom, which was actually sort of innovative at the time, since action games on computers and consoles were still very much take-the-quarter arcade oriented.  I miss the concept of “score” in a lot of games today, but I think the finite and granular nature of the enemies, tasks, and items in Wolf is better suited to end-of-level stats, so I removed both lives and score, but added persistent awards for par time, 100% kills, 100% secrets, and 100% treasures.  The award alone wasn’t enough incentive to make treasures relevant, so I turned them into uncapped +1 health crumbs, which makes you always happy to find them.


I increased the pickup radius for items, which avoided the mild frustration of having to sometimes make a couple passes at an item when you are cleaning up a room full of stuff.


I doubled the starting ammo on a fresh level start.  If a player just got killed, it isn’t good to frustrate them even more with a severe ammo conservation constraint.  There was some debate about the right way to handle death:  respawn with the level as is (good in that you can keep making progress if you just get one more shot off each time, bad in that weapon pickups are no longer available), respawn just as you entered the level (good — keep your machinegun / chaingun, bad — you might have 1 health), or, what I chose, restart the map with basic stats just as if you had started the map from the menu.


There are 60 levels in the original Wolf dataset, and I wanted people to have the freedom to easily jump around between different levels and skills, so there is no enforcement of starting at the beginning.  The challenge is to /complete /a level, not /get to/ a level.  It is fun to start filling in the grid of level completions and awards, and it often feels better to try a different level after a death.  The only exception to the start-anywhere option is that you must find the entrance to the secret levels before you can start a new game there.


In watching the early testers, the biggest issue I saw was people sliding off doors before they opened, and having to maneuver back around to go through.  In Wolf, as far as collision detection was concerned, everything was just a 64×64 tile map that was either solid or passable. 

Doors changed the tile state when they completed opening or began closing.  There was discussion about magnetizing the view angle towards doors, or somehow beveling the areas around the doors, but it turned out to be pretty easy to make the door tiles only have a solid central core against the player, so players would slide into the “notch” with the door until it opened.  This made a huge improvement in playability.


There is definitely something to be said for a game that loads in a few seconds, with automatic save of your position when you exit.  I did a lot of testing by playing the game, exiting to take notes in the iPhone notepad, then restarting Wolf to resume playing.  Not having to skip through animated logos at the start is nice.  We got this pretty much by accident with the very small and simple nature of Wolf, but I think it is worth specifically optimizing for in future titles.


The original point of this project was to investigate FPS control schemes for the iPhone, and a lot of testing was done with different schemes and parameters.  I was sort of hoping that there would be one “obviously correct” way to control it, but it doesn’t turn out to be the case.


For a casual first time player, it is clearly best to have a single forward / back / turn control stick and a fire button.


Tilt control is confusing for first exposure to the game, but I think it does add to the fun factor when you use it.  I like the tilt-to-move option, but people that play a lot of driving games on the iPhone seem to like tilt-to-turn, where you are sort of driving BJ through the levels.  Tilt needs a decent deadband, and a little bit of filtering is good.  I was surprised that the precision on the accelerometer was only a couple degrees, which makes it poorly suited for any direct mapped usage, but it works well enough as a relative speed control.


Serious console gamers tend to take to the “dual stick” control modes easily for movement, but the placement of the fire button is problematic.  Using an index finger to fire is effective but uncomfortable.  I see many players just move the thumb to fire, using strafe movement for fine tuning aim.  It is almost tempting to try to hijack the side volume switch for fire, but the ergonomics aren’t quite right, and it would be very un-Apple-like, and wouldn’t be available on the iPod touch (plus I couldn’t figure out how…).


We tried a tilt-forward to fire to allow you to keep your thumbs on the dual control sticks, but it didn’t work out very well.  Forward / back tilt has the inherent variable holding angle problem for anything, and a binary transition point is hard for people to hold without continuous feedback.  Better visual feedback on the current angle and trip point would help, but we didn’t pursue it much.  For a game with just, say, a rocket launcher, shake/shove-to-fire might be interesting, but it isn’t any good for wolf.


It was critical for the control sticks to be analog, since digital direction pads have proven quite ineffective on touch screens due to progressive lack of registration during play.  With an analog stick, the player has continuous visual feedback of the stick position in most cases, so they can self correct.  Tuning the deadband and slide off behavior are important.


Level design criteria has advanced a lot since Wolfenstein, but I wasn’t going to open up the option of us modifying the levels, even though the start of the first level is painfully bad for a first time player, with the tiny, symmetric rooms for them to get their nose mashed into walls and turned around in.  The idea is that you started the game in a prison cell after bashing your guard over the head, but even with the exact same game tools, we would lead the player through the experience much better now.  Some of the levels are still great fun to play, and it is interesting to read Tom Hall and John Romero’s designer notes in the old hint manuals, but the truth is that some levels were scrubbed out in only a couple hours, unlike the long process of testing and adjustment that goes on today.


It was only after I thought I was basically done with the game that Tim Willits pointed out the elephant in the gameplay room — for 95% of players, wandering around lost in a maze isn’t very much fun. 

Implementing an automap was pretty straightforward, and it probably added more to the enjoyment of the game than anything else.  Before adding this, I thought that only a truly negligible amount of people would actually finish all 60 levels, but now I think there might be enough people that get through them to justify bringing the Spear of Destiny levels over later.


When I was first thinking about the project I sort of assumed that we wouldn’t bother with music, but Wolf3D Redux already had code that converted the old id music format into ogg, so we would up with support at the beginning, and it turned out pretty good.  We wound up ripping the red book audio tracks from one of the later commercial Wolf releases and encoding at a different bitrate, but I probably wouldn’t have bothered if not for the initial support.  It would have been nice to re-record the music with a high quality MIDI synth, but we didn’t have the original MIDI source, and Christian said that the conversion back from the id music format to midi was a little spotty, and would take a fair amount of work to get right.  I emailed Bobby Prince, the original composer, to see if he had any high quality versions still around, but he didn’t get back with me.


The game is definitely simplistic by modern standards, but it still has its moments.  Getting the drop on a brown shirt just as he is pulling his pistol from the holster.  Making an SS do the “twitchy dance” with your machine gun.  Rounding a corner and unloading your weapon on … a potted plant.  Simplistic plays well on the iPhone.


*Programming notes*


Cass and I got the game running on the iPhone very quickly, but I was a little disappointed that various issues around the graphics driver, the input processing, and the process scheduling meant that doing a locked-at-60-hz game on the iPhone wasn’t really possible.  I hope to take these up with Apple at some point in the future, but it meant that Wolf would be a roughly two tick game.  It is only “roughly” because there is no swapinterval support, and the timer scheduling has a lot of variability in it.  It doesn’t seem to matter all that much, the play is still smooth and fun, but I would have liked to at least contrast it with the perfect limit case.


It turns out that there were a couple issues that required work even at 30hz.  For a game like Wolf, any PC that is in use today is essentially infinitely fast, and the Wolf3D Redux code did some things that were convenient but wasteful.  That is often exactly the right thing to do, but the iPhone isn’t quite as infinitely fast as a desktop PC.


Wolfenstein (and Doom) originally drew the characters as sparse stretched columns of solid pixels (vertical instead of horizontal for efficiency in interleaved planar mode-X VGA), but OpenGL versions need to generate a square texture with transparent pixels.  Typically this is then drawn by either alpha blending or alpha testing a big quad that is mostly empty space.  You could play through several early levels of Wolf without this being a problem, but in later levels there are often large fields of dozens of items that stack up to enough overdraw to max out the GPU and drop the framerate to 20 fps.  The solution is to bound the solid pixels in the texture and only draw that restricted area, which solves the problem with most items, but Wolf has a few different heavily used ceiling lamp textures that have a small lamp at the top and a thin but full width shadow at the bottom.  A single bounds doesn’t exclude many texels, so I wound up including two bounds, which made them render many times faster.


The other problem was CPU related.  Wolf3d Redux used the original ray casting scheme to find out which walls were visible, then called a routine to draw each wall tile with OpenGL calls.  The code looked something like this:


DrawWall( int wallNum ) {

    char   name[128];

    texture_t   *tex;

    sprintf( name, “walls/%d.tga”, wallNum );

    tex = FindTexture( name );



texture_t FindTexture( const char *name ) {

    int   i;

    for ( i = 0 ; i < numTextures ; i++ ) {

       if ( !strcmp( name, texture[name]->name ) ) {

          return texture[name];






I winced when I saw that at the top of the instruments profile, but again, you could play all the early levels that only had twenty or thirty visible tiles at a time without it actually being a problem. 

However, some later levels with huge open areas could have over a hundred visible tiles, and that led to 20hz again.  The solution was a trivial change to something resembling:


DrawWall( int wallNum ) {

    texture_t   *tex = wallTextures[wallNum];




Wolf3D Redux included a utility that extracted the variously packed media from the original games and turned them into cleaner files with modern formats.  Unfortunately, an attempt at increasing the quality of the original art assets by using hq2x graphics scaling to turn the 64×64 art into better filtered 128×128 arts was causing lots of sprites to have fringes around them due to incorrect handling of alpha borders.  It wasn’t possible to fix it up at load time, so I had to do the proper outline-with-color-but-0-alpha operations in a modified version of the extractor.  I also decided to do all the format conversion and mip generation there, so there was no significant CPU time spent during texture loading, helping to keep the load time down.  I experimented with the PVRTC formats, but while it would have been ok for the walls, unlike with DXT you can’t get a lossless alpha mask out of it, so it wouldn’t have worked for the sprites.  Besides, you really don’t want to mess with the carefully chosen pixels in a 64×64 block very much when you scale it larger than the screen on occasion.


I also had to make one last minute hack change to the original media — the Red Cross organization had asserted their trademark rights over red crosses (sigh) some time after we released the original Wolfenstein 3D game, and all new game releases must not use red crosses on white backgrounds as health symbols.  One single, solitary sprite graphic got modified for this release.


User interface code was the first thing I started making other programmers do at Id when I no longer had to write every line of code in a project, because I usually find it tedious and unrewarding.  This was such a small project that I went ahead and did it myself, and I learned an interesting little thing.  Traditionally, UI code has separate drawing and input processing code, but on a touchscreen device, it often works well to do a combined “immediate mode interface”, with code like this:


if ( DrawPicWithTouch( x, y, w, h, name ) ) {

    menuState = newState;



Doing that for the floating user gameplay input controls would introduce a frame of response latency, but for menus and such, it works very well.


One of the worst moments during the development was when I was getting ready to hook up the automatic savegame on app exit.  There wasn’t any savegame code.  I went back and grabbed the original 16 bit dos code for load / save game, but when I compiled I found out that the Wolf3d Redux codebase had changed a lot more than just the near / far pointer issues, asm code, and comment blocks.  The changes were sensible things, like grouping more variables into structures and defining enums for more things, but it did mean that I wasn’t dealing with the commercially tested core that I thought I was.  It also meant that I was a lot more concerned about a strange enemy lerping through the world bug I had seen a couple times.


I seriously considered going back to the virgin codebase and reimplementing the OpenGL rendering from scratch.  The other thing that bothered me about the Redux codebase was that it was basically a graft of the Wolf3D code into the middle of a gutted Quake 2 codebase.  This was cool in some ways, because it gave us a console, cvars, and the system / OpenGL portable framework, and it was clear the original intention was to move towards multiplayer functionality, but it was a lot of bloat.  The original wolf code was only a few dozen C files, while the framework around it here was several times that.


Looking through the original code brought back some memories.  I stopped signing code files years ago, but the top of WL_MAIN.C made me smile:





                           WOLFENSTEIN 3-D


                      An Id Software production


                           by John Carmack





It wasn’t dated, but that would have been in 1991.


In the end, I decided to stick with the Redux codebase, but I got a lot more free with hacking big chunks of it out.  I reimplemented load / save game (fixing the inevitable pointer bugs involved), and by littering asserts throughout the code, I tracked the other problem down to an issue with making a signed comparison against one of the new enum types that compare as unsigned.  I’m still not positive if this was the right call, since the codebase is sort of a mess with lots of vestigial code that doesn’t really do anything, and I don’t have time to clean it all up right now.


Of course, someone else is welcome to do that.  The full source code for the commercial app is available on the web site.  There was a little thought given to the fact that if I had reverted to the virgin source, the project wouldn’t be required to be under the GPL.  Wolf and the app store presents a sort of unique situation — a user can’t just compile the code and choose not to pay for the app, because most users aren’t registered developers, and the data isn’t readily available, but there is actually some level of commercial risk in the fast-moving iPhone development community.  It will not be hard to take the code that is already fun to play, pull a bunch of fun things off the net out of various projects people have done with the code over the years, dust off some old map editors, and load up with some modern quality art and sound.


Everyone is perfectly within their rights to go do that, and they can aggressively try to bury the original game if they want.  However, I think there is actually a pretty good opportunity for cooperation.  If anyone makes a quality product and links to the original Wolf app, we can start having links to “wolf derived” or “wolf related” projects. 

That should turn out to be a win for everyone.


I’m going back to Rage for a while, but I do expect Classic Doom to come fairly soon for the iPhone.

3 Tools for Better Mobile Coding Endurance

Control your Fans

We trainers and programmers might have many geek groupies, but this time I am not talking about those. 😉 The second thing to take control of is the fans that keep your CPU cool. Those rotating fans have motors that are putting a small but constant load on your battery.

Using the “About this Mac” page I was able to determine the difference between full fan speed  and lowest fan speed to be up to 100 mA. Compared to the regular energy use of around 1300 mA this gives you up to 15 minutes more working time.

Fan Control

My favorite tool to help you take control has the obvious name “Fan Control” and is available for free from Lobotomo. With this you don’t set the speed directly but with three sliders you adjust the red line which determines the RPM to use for a given CPU temperature.

Real Geeks Undervolt

While playing with settings like fan speed might have an impact on available idle time there is little you can (usually) do to extend battery time when doing something useful. Typing code lets your CPU idle most of the time anyway.

The last bastion to tackle if you posess the strong determination of geeks is undervolting your CPU. We all know that Watt = Volt times Ampere. So if we can manage to decrease the Volts necessary for the CPU then also the energy usage under load will decrease.

The tool for this purpose is CoolBook Controller which gives you such control for the price of $10. At the maximum load the CPU is using 1.1375 Volts default. CoolBook Controller has a built in testing facility that allows you to decrease the Volts for a given frequency. This way I found that my MBP can also work with 2500 MHz with as low as 1.01V, but then it would get unstable.

CoolBook Controller

In real life you would only decrease the voltage by two or three steps to not risk the system becoming unstable under stress. The makers have achieved up to 14 degrees of difference in temperature under stress. Less temperature also equals less cooling required.

But like all things concerning over-clocking or under-volting this is not for the faint of heart.

Warranty Replacement Battery Tool

According to Apple the 15″ MacBook Pro Battery is designed to retain 80% of its factory capacity after 300 loading cycles. If you are using your MBP daily and constantly like me then this number equates to approximately 6 months.

The original capacity of my (early 2008 model) MacBook Pro Battery was 5400 mAh but as of this writing it is decreased to 3112 mAh. This is way less than the 80% (4320 mAh) that are normal.

Ordinarily it would be difficult to prove to Apple that you get much less than the 3 hours of working time advertised. If it weren’t for the fabulous and free tool Coconut Battery which makes it crystal clear.
Coconut Battery Tool

Having only slightly more than half the original capacity starts to cause me problems because this means that my two hour train rides are no longer fully covered. Obviously I am going to go to my Apple authorized dealer later and send it in for warranty exchange.

Finally a Piece of Advice

Once you have gotten a new battery then you should try to discharge it fully before fully loading it. This helps to retain the maximum possible capacity. These days many people use a MacBook as Desktop replacement keeping it constantly connected to the power adapter.

The jury is still out whether such practise is good or harmful for the battery. Modern battery management should be able to minimize impact and the latest models of MacBooks don’t even allow for removal of the battery out of paranoia.

But what you should do in any case is this: at least once a week is to fully discharge your battery before fully loading at again. This “battery training” exercise allows the battery management system to calibrate and “keeps the battery juices flowing” (Apple lingo, not mine)

And all of this will increase your mobile coding stamina to its maximum, pumping those heavy Cocoa objects. Maybe just enough to have a syntax orgasm the next time you are coding on a train or plane. Good Luck!