Race and Vehicle Simulations

Back in December 2011 I conducted an interview with Stefano Casillo of Kunos Simulazioni in AutoSimSport magazine. At the time, it was cut into two parts, primarily because there was so much to talk about. We were discussing the story of netKar Pro, how it came to be, the events surrounding its conception and some of the personal challenges Stefano endured during its genesis.  Part one of the interview, if you missed it, can be picked up from the December 2011 issue on www.autosimsport.net , but to fill you in, part one ended with the eventual release of netKar Pro to the public. A moment that should have been marked by relief for Stefano, I sat down with him to talk about how it went.

Jon Denton: So, Stefano, cast your mind back to that fresh spring in April 2006, the day of release of netKar Pro V1.0 is coming, how are you feeling?

Stefano Casillo: Very tired and very nervous, I spent the afternoon lapping in multiplayer with Simone.  I was nervous but unaware of the hell that was about to break loose!

Jon Denton:  April 10th was the big day. Did the sim take off in terms of purchases and downloads, or was it a slow burn?

Stefano Casillo: We had a good number of pre-orders, then on the release date sales were going very good for the first couple of hours.  Then forums started to fill up with not so good comments.  DrivingItalia.net (DI.net) was our main forum for Italian players, and there was an English section too, but the main English audience were on RaceSimCentral (RSC).  On that night DI.net was packed with people.

The final blow, for me, was that there was a crack released 3-4 days after release.  That pretty much killed it off in my mind.

Jon Denton: Crack for the demo download?

Stefano Casillo: Yea, the crack to unlock the full game from the demo.

For those that were not aware, at the time a single car, single track demo was released for netKar Pro, to give drivers a feel for the sim. There was no multiplayer, and options were limited, with some of the nicer sim elements missing, such as the AIM display.  This was a cut down version of the full game .EXE, as such, talented hackers were soon onto the case to break open the chest and merrily assume that all of the world should be theirs for free.

Jon Denton: Did the crack really hit sales? Or was it more for the casual pirate?

Stefano Casillo: It really does hit the sales, and it really hit my morale.  When you put blood and sweat into something, to have people just rip it off is hard on the heart.  It was the first experience for me of this sort of thing, now I have a more pragmatic approach, I know it is going to happen and I live with it.  I dont even bother working out a smart way to protect the software, copy protection is there, but it’s not that hard to figure out.

Jon Denton: Pirates will always find a way around it

Stefano Casillo: Yea, it’s wasted time, better to use the few remaining brain cells for the sim.

Jon Denton: So, was the forum reaction all bad news? I must admit, I had run a few versions prior to V1.0 and had no technical problems at all, was I just lucky?

Stefano Casillo: We ran together, in those early days, we had the chance to explain to you what was going on over Skype, which would be a big help in the learning curve. Plus you and the other AutoSimSport guys have been driving sims for years, as well as having a sound understanding of motorsport and how things work.

The fact is, netKar Pro is really bad at explaining what is going on.  The technical aspects of the sim were quite a way above what was around at the time, or even now.  As such, what may be simple to a real life driver like “release the gas to change up”, or remembering to make sure you refilled your fuel tank or changed tyres when you went back to the pits were unexplained.  The gearbox modelling was pretty hard-core, and took a lot of practice. If you imagine back then people were driving sims where you could flat-shift and never had to blip on downshifts, we maybe expected too much of the player base for them to pick all this stuff up without any tutorials or information. There was also no real manual at release.

But if you have somebody talking you through it, then it, sort of, makes more sense.

Jon Denton: Well, it’s simple though, right, you have cars, you have tracks, and you drive on them?

Stefano Casillo: Maybe, but no racing sim had ever asked anyone to start the car manually, let alone without telling them which switch on the dashboard starts the car!  Then, of course, if you didn’t start it properly, with the right amount of throttle, it would stall. A few attempts at that and your battery would run flat, and that was that.  With no manual or tutorial or in game instructions the “green” driver was in trouble.

Jon Denton: Some of these things, of course are things that, if you actually drive a car, are not that hard to grasp. Some simulators need one to learn a vehicle to really get to grips with it. Many a flight sim can throw you into a “cold and dark” aircraft and you would not know where to start, however, on the most part such sims come with an “easy mode” where all of that “actually being a pilot” stuff is done for you, and in the sims where this is not an option, there is always a hefty manual to explain the ins and outs.  For such a complex simulator to throw a player in at the deep end like this was quite an oversight.  But simracers, they love a challenge, right?  Using the grey matter to learn a thing or two about real racing cars was a chance to relish, no?

Stefano Casillo: Maybe for some, but most people approach a (sim) game as a game.  If something doesn’t work they perceive it as a bug, not as a feature.  If the car won’t start something must be wrong with the software, not with what they are doing, and with no documentation to tell them otherwise, it’s understandable.

For example, the original sim modelled flat spots on the tyres very noticeably. And let’s be fair, the first time you drive a sim and get used to the controls, you will lock up the odd tyre here and there.  As such, by the time just about anyone started their first flying lap in the sim, the front tyres were like a fifty pence coin, and the steering wheel would be shaking in your hands. Realism.  But, well, my inbox was full of emails saying: “The Force Feedback is shit, it just shakes like crazy, no feeling”, change your tyres mate.

Stefano Casillo: in Assetto Corsa (AC) we are planning to give visual feedback to everything that is happening in the sim, if you bend a suspension arm, there must be something on screen telling you that fact so you don’t think your steering wheel is broken, or you need new drivers, or something.  I think we got it backwards in 2006, it should be possible to make a hard-core sim work in the marketplace, but you have to educate the driver. If we make the sim accessible first for the beginner, then, if they want to get serious, give them a series of switches in the options menu to ramp things up.

Jon Denton: There’s a reason FSX has ten tutorials!  So would you say that a lot of the issues you had with netKar Pro initially were this type of problem, or were there a lot of hardware bugs, and the like, too?

Stefano Casillo: Hardware compatibility and stability of the software has always been ok.  The biggies were the infamous “Scazzato” sound engine that just didn’t work on some machines.

Jon Denton: Ah yes, I remember it. An interesting feature, not yet repeated, it worked very well to help a driver understand what the engine was doing. But it did not have the atmospherics of sims like GTR at the time.

Stefano Casillo: Yes, very low level audio programming, bytes and buffers, I am not that good at these things.  Same reason perhaps I struggle with netcode, it’s a tad too low level for my taste.  The Scazzato sound engine had tiny samples for a single “bang” in a cylinder, and then these were mixed into the software at the right rate mixing different bangs for exhaust noise and intake noise.

Jon Denton: Do you think this is something that, one day, could make a comeback in a car simulator? Or is it too much tech for not enough gain?

Stefano Casillo: It’s hard to say, there are companies doing amazing stuff.  Like those speakers you can get in your car to make it sound like a Ferrari 430! Lol.

Jon Denton: So, 14 days later, April 24th 2006, V1.01 was released, did it save the world?

Stefano Casillo: It did sort out the most urgent problems. Lots of license activation problems with Nordic characters, Spanish characters and so on.  I think it also fixed the fact that every car in multiplayer had the default skin!

Jon Denton: At the time the online servers were busy, but scarce. You would see people pop in, crash, then leave, lots of times.  Newcomers seemed to be struggling. Some of us were punting around doing lap after lap, others seemed to be really struggling with the sim. Do you think this was the lack of information primarily? I don’t think, personally, driving wise, it was much more difficult than other sims at the time.

Stefano Casillo: I think it was different; most people were used to F1 racers like Crammond’s or ISI F1 games.  Pretty much every developer had an F1 like car in their sim, our cars were something very different, everything in netkar Pro was so different from other sims.  You were free to start your car and go around while the starting light was red, no one was telling you what to do, you had to manually hit the “go to grid” button, in the current version that button is flashing green but back in v1.0 it was just a button.

Jon Denton: It amazes me that such little things cause such problems. Do some people really sit there just waiting for the machine to tell them what to do?

Stefano Casillo: It can be really confusing absolutely.  As well as this, I think the driving was quite tricky. The tyre model was not very good in v1.0, the cars were twitchy, very weird at high slip angles.

Jon Denton: Why was this? The initial model was very Pacejka based, no?

Stefano Casillo: Yes

Jon Denton: Early versions also exhibited the weird “slide down a hill when stopped” thing.

Stefano Casillo: Well that’s a sim problem that is there in different forms and gravity in every product.  It’s really hard to stop a car in a physics simulation with discrete time steps.  At the moment AC is quite good at it, because the nature of the tyre model is not static.

The problem is that tyre models are based on the concept of slip percentage.  Which is basically a division between the rotation speed of the tyre and the speed of the wheel hub, as the hub speed goes to zero when you are stopping, the result of the division goes up to infinity.  At pure zero kmh, it is not even defined, and the software will crash.  So what you do is select a very low speed where you just say “ok the car is stationary” and stop the simulation freezing the car, if that speed is too slow, it might never be reached if you are standing on a hill, thus, you keep sliding down that hill.

Jon Denton: This naturally meant there were people saying “not realistic.” I would say, however, the tyre model at speed was superior to any of the sims on the market in 2006, would you agree?

Stefano Casillo: Yea, I always say my sims are only realistic over 15 kmh, lol!  Under 15 kmh, you are in the land of pure hackage.  As I said, AC is much better, I think it is not bad even at 3-4 kmh.

Jon Denton: Based on my brief try back in March I would agree (See AutoSimSport March 2012 edition).

Jon Denton: So the online code came in for a lot of flak, my personal experience was that it worked ok if there were low pings, but if you wanted to race someone in the US, forget it. This seemed to be the biggest complaint in the community. What went wrong?

Stefano Casillo: Netcode is hard, very hard, it’s very asynchronous, so very hard to test.  To test it properly you’ll have to ring somebody in the US.  The internet is the least reliable network in the world, sadly, and this makes netcode such a hard thing to do.  It’s totally unreliable and, even if it is reliable you still need to guess where a car is now based on information that is 200ms old.  200ms dont sound that much, but at 150kmh your typical high speed corner velocity  you can be anywhere in a circle of 8 meters.  Hence, if it goes wrong you see cars inside cars, and flying bouncing chaos. So when people complain of a ghost collision showing me a screen shot saying “look there was some good 2-5 cm between me and him” I can only lol.

Jon Denton: Yes, it’s an incredibly difficult thing to get right. Not helped by bigger development teams like ISI and Papyrus doing it so well.

Stefano Casillo: I have profound respect for my competitors in this area because what games like iRacing and rFactor do with netcode is truly an amazing achievement.  It’s not a subject covered in literature, there may be lots of information out there about the Quake 3 netcode, but come on, that’s easy-easy-easy compared to a car.

Jon Denton: Indeed. No one wants to run around in Quake inches from each other.

Stefano Casillo: Your typical FPS character is moving at constant speed, a race car not only is NEVER at a constant speed, it’s not even at constant acceleration!  It’s a software nightmare materialized I am telling you!!

Jon Denton: So the plan was to try to fix this for the next release, more sleepless nights.  V1.02 was released, in October 2006, and had some high expectations. If I recall this release was quite an improvement?

Stefano Casillo: Yea sure, 1.0.2 was a step in the right direction, but nothing massive. Jaap Wagenvoort and the GPC league guys got involved with online testing for V1.03.

By this stage I was really burned out, so I left it all behind and went to Vietnam to rethink my life, for two months, to forget about RSC hate posts for a while!  I remember lovely things like: “oh gosh, the sim has bugs and he goes to Vietnam.. let’s kill him!!!” Lol.

Jon Denton: Development seemed to go quiet for quite a while then. The gap between V1.02 and V1.03 was nearly two years. It led many to think that Kunos had abandoned the community of people that had purchased their sim. Was this the case? Or were you hard at it?

Stefano Casillo: I have to be honest; I almost gave up on netkar as a “gaming” sim.  During that period I was doing very cool stuff with BRD that literally saved us from going down in flames.

Our contract with BRD was 2 years, and there you can do the math with the time between 1.0.2 and 1.0.3.  After 2 years me and Marco (Massarutto, Production Director at Kunos Simulazioni) just sat down and had to decide what to do.  We thought we could still have our say in the “game” sim racing world, as opposed to motorsport industry simulations, so we decided to re-join the fight. I started work on “saving” netKar Pro, while Marco set to work on what we could do after netKar.

Jon Denton: So the time with BRD was spent developing the sim core for motorsports customers? Or more for motion sims and the like? Or stuff you can’t talk about?

Stefano Casillo: It was a bit of everything, we worked on an amazing BRD motion platform, worked for Honda F1 on their simulator, we had a BMW X3 at London Victoria station with our sim, it was all cool, cool stuff.  We also did the Singtel simulation, which was the first F1 car in the netKar Pro sim.

Jon Denton: And was 1.03 the saviour? I seem to remember running in the GPC league with it. The netcode was very much better than in the first versions.

Stefano Casillo: Yes v1.0.3 was netKar Pro as it was supposed to be at v1.0, and also the last “pure” netKar pro.  With “full mode”, gearbox modelling, etc.  Jaap and his guys helped a LOT for v1.0.3, we tested night after night with the guys from GPC, he wrote the amazing manual, and developed the GPOS website software, which allowed driver stats, etc. Linked with nKRank it is all in use to this day.

I miss you Jaap :p

Jon Denton: V1.03 seemed to have some happy customers. V1.1 was nearly another two years, and yet the features decreased (but the GUI changed), What happened?

Stefano Casillo: We started to look into ways to expand the audience for netKar Pro, we felt the GUI was a big obstacle, it was really scaring people away.

Jon Denton: But it was Windows!?

Stefano Casillo: Yes, but it wasn’t a “game,” I still love the 1.0.3 interface, people were scared away by thinking it was more of a professional simulator, than a game you can have fun with.

For a long time I used a similar interface for AC during development.  We called it the “AC Shell,” I love those things, but I came to accept the fact that the majority of people don’t.

Jon Denton: It’s a shame there can’t be an option.

Stefano Casillo: I agree, perhaps I will release the AC Shell open source so modders can make something similar for AC.

Jon Denton: Also, things like the gearbox simulation and full mode were removed. Auto car start-up was added (as a menu option, thankfully), and a much better interface for controller setup. Some good, but why did the hard core stuff have to go away for the people that may have wanted it?

Stefano Casillo: Because it was a lot of work, at that time I was changing the entire setup system and making it work with the full mode gave me daily headaches.  Eventually, I had to choose between throwing weeks of work away on the new setup system and revert to the old one, or let full mode go.

Jon Denton: It’s a shame, I still think the gearboxes were the best I have known in sims, you had to drive *properly*.  Of course, this does not always work for people with different controllers, without a clutch, and so on.

Stefano Casillo: True, the real problem was that the netKar source code was (is) impossible to work with.  In 2001 when I started it I was all about “code, code, code, just code and make it work”, I have learned the lesson, and in the last 3 years I have been really into software architecture and studying more about organizing big projects.

Jon Denton: So netKar grew up, in a sense, with you. In that the base of the product started out as a hobby, but the seeds of that were impossible to work round as the product grew into a much bigger monster.

It struck me, though, that after V1.1 there were more people playing, I think the community had changed quite a lot by then and was less “hard core” in its make-up. There were, and are now, a lot more people and not all of them serious car enthusiasts

Stefano Casillo: I think, with V1.1, the software was better, the presentation was better and it took care of the user a bit more.  The tyre model was better, and more drivable,  every netKar release has lots of improvements in the tyre model.

Jon Denton: It definitely was more like a game than something you might find in a dark room at McLaren.

So you constantly worked on the tyres? A tyre modeller’s work is never done!  What were the key challenges? As you said, the early releases were a bit edgy to drive. Was the focus on making a more malleable tyre?

Stefano Casillo: Basically, a tyre with less parameters.  Pacejka is a monster of something like 100+ parameters, every parameter can potentially screw something up, and realistically, you never have the raw data available to even try to get those 100+ parameters.

To fix this I tried to build a tyre model that has a physical based theory in the formulas and that can be tweaked with very few parameters that cannot create anything “destructive.”  This involved moving away from that particular pacejka model.  The basic pacejka “magic formula” is still valid to create basic curves, but a good tyre model needs to be more dynamic. The model we see in netKar Pro V1.3, Ferrari Virtual Academy (FVA), and AC are all based on the idea of generating a “base” slip curve that is then adapted to the behaviour of the tyre.  I call it “slip profile,” in netKar Pro and FVA this adaptation is done in steady state analysis, in AC I added the dynamic of the carcass and thread to the equations.

This not only makes the tyre more dynamic when put in extreme situations, like riding kerbs and so on, but also makes a big difference on flat roads, in the way it reacts to load transfer when you turn the steering wheel.  I makes it feel…  Rubbery.

Jon Denton:  V1.2 came along in November 2010. It felt like an evolution of V1.1 mainly. But the Formula KS2 was added.  This was the “almost F1 ” car that many had been waiting for, but also things felt a little more solid from the tyre point of view, was much changed?

Stefano Casillo: FVA came out in September 2010, I knew a lot of people would buy FVA and would find it hard to go back to racing the F2000 or Formula Target in netKar.  After a year working on FVA I tried netKar and it all felt like slow motion!  So I just called the car graphics guy and I told him: “I need a fast bad single-seater, next week.”

Jon Denton: I raced it in a few series, (even got a win!). I think it ranges as one of my favourite sim cars ever.

Stefano Casillo: What changed really in V1.2 was just more polishing of the tyre model, thanks to a lot of very tasty data fresh from Ferrari. Every time I can get my hands on new data, something pops in my head and some magic relationship with some other data I saw becomes evident and a new formula is born.

Jon Denton: Racing the KS2 was so demanding; incredibly fast, obviously, it brought tyre management to the fore as races could be a bit longer than in the Formula Target. Keeping the tyres “sweet” really became something about “feel” for me, you would find part of a race when different drivers were quick. The more experienced would always adapt fastest to the changes in the tyre throughout its lifecycle.  Real, nice, hard core simming stuff.

Stefano Casillo: It was a very well balanced car, very cool to drive, very demanding for the netcode though, because of its crazy rate of acceleration.

Jon Denton: By now it struck me there was a whole new world in simracing. iRacing was getting busier and busier and the niche communities of netKar Pro racers were like a small family. You would race with the same people in different leagues sometimes. Amongst this some very serious followers developed, and you became regarded as one of the greats of simracing. How does that feel?

Stefano Casillo: It still feels strange.  The period between 2006-2008 really had a big effect on me.  Back then when I read “kunos” or “netKar” on a forum I always had to brace for impact.   It’s weird to see now, that netKar is considered as a point of reference for sims.

Jon Denton: Almost *THE* point of reference when it comes to tyre model and driving feel.

Stefano Casillo: It feels good, It makes me feel that not going full in for the “professional” market but staying in simracing in 2008 was a good call. I only wish I had made something like v1.3 in 2006 to release, then history would have been different.

Jon Denton: So V1.3 came along with another new car, the Shelby, and Trento Bondone, the Osella, and RAIN!?  As well as hugely improved netcode. You threw it all at us!?

Stefano Casillo: The last netKar, V1.3 was a very good step forward online, I understood how important time sync really is in netcode, which made things a lot smoother. From this I now have a new smoothing algorithm planned on paper, hopefully it’ll be a step forward.

We wanted to end the netKar journey with a bang, we knew it was going to be the last netKar pro, so we went all in. Simone wanted to have a go at car modelling and so he did the vintage, you’ve got to love the guy, he is arguably the best track modeller in the business but still loves to challenge himself.

Jon Denton: And why not. It’s a beautiful car.  But then Aris (Vasilakos) came along and gave it slicks and suspension!

Stefano Casillo: Yes, the big comeback of the flying pig, LOL!

Jon Denton: Simone has been with Kunos since the start, no? You and Marco must have had some up’s and downs over the years too. Has the team always been like a family?

Stefano Casillo: We “lost” a “family” member on the road, Alessandro “outrunner” Piemontesi, who did many things for netKar free and was part of the initial team for netKar PRO.  Sadly, going from free software to a business can create frictions and sadly that happened.  Also, Aris was in the initial team but he quickly got fed up with my control freak attitude and left.  Things are much more solid now, no big egos.  I used to be a pain on the physics, never wanted to leave it alone.  But Aris has gained my trust 100% for what he did on P&G (Aris worked on the car physics for the famous P&G GTR2 historic mod), on FVA, and the way he is pushing the right directions with AC.  So here I am, I am just a code monkey now. 😀

Jon Denton: So netKar Pro is, as it stands, a defining racing sim of the previous generation. There are many eager souls waiting for the next generation as we speak. I guess you never thought it would be so revered. Do you think it will always be remembered as a bit of a rough diamond?

Stefano Casillo: I hope people will remember it.  It is rough, it has a lot of attitude, some of it a bit tamed now, but still has an attitude.  It’s like trying a drop shot volley at Wimbledon, you can end up looking like an idiot or like a hero, but at least you tried.

Jon Denton: It is a superb piece of work, which, for me, from the first few laps felt very natural and understandable in the way it communicated to the driver. It still features some aspects that no other sim has touched (dirt on visor, clickable cockpits), and the driving experience is still yet to be bettered I think.

Stefano Casillo: After ten years of reading simracing forums I think we are almost there at cracking the code!

Jon Denton: I don’t think the simracing forum will ever be a place where there are lots of people saying “This could never be improved, I am in love”, sadly. I suppose a happy game forum is an empty game forum.

Well, that’s netKar Pro, 6 years of driving pleasure. Has it been tombstoned as software, or could there be further development?

Stefano Casillo: I don’t think I’ll do major improvements on it, but some minor tweaks might appear.

Jon Denton: These six years have gone in a flash eh?

Stefano Casillo: Yes and no.  So many things happened, it also feels a long time ago that all this started.  11 years of netKar since 2001 are incredible though.

Jon Denton: Do you still drive netKar Pro now?

Stefano Casillo: No, I am so crazy, busy trying to get AC out this year I just have time for AC and some occasional guitar playing.  Since June we had to change gear and get more hours in, and things are going to get worse the more we approach winter.

Jon Denton: I don’t need to tell you the expectation in the community for AC is very, very high. It feels like a similar time to 2005/6, when nothing truly awesome had come our way for a while, simracers were discontented with the current offerings and gasping for something new. You’ve got to do it all over again!

Stefano Casillo: I hope people don’t set their expectations too high for AC, it’s a brand new piece of software, the aim is to get a very SOLID release on v1.0. I would rather to leave a feature out of the sim than release it with bugs. It’s a first step into the next 5 years of PC simracing.  We have to enjoy the PC while there is still something called PC!