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My Impression
10-25-2006, 10:43 PM,
#1
My Impression
Hello Developers!

First off thank for to everyone especially "thelusiv" on helping me on some installation problems. After some tingkering I am able to play the game. (I've also tried it on a Windows machine, pretty easy).

Now keep in mind I am only using a mouse and keyboard to play this game, I don't know if a better gameplay can be expericed with a steering wheel & pedals.

On to the game!

I have to ask; is this mainly a pure simulation or a game? I ask because this would be under the category of simulation, something that racers, drivers ed would us in prime time. If the purpose is at game, I think a lot of people will get bored quickly (I am no gamer, so I'll leave it at that).

Physics
The car physics are there, not all of them but most are there. It's a Grand Tourismo 2-3 physics. I am glad to see there are some key difference on cars such as the BMWGTR and the Toyota GT4 Rally car.

Oh I think I found a bug, I hit a mountain side of norclief (sp?) and my car just kept on rolling into an infinate loop; I was only seeing Sky and grass, had to terminate the game.

Tires
I know this is a "Drift" simulation/games, one cannot assume that drifters rely on tractionless tires. This is entirely false. In drifting, the driver relies on the adhesion of the tire, find the limit of the tires and go beyond that.

It seems like theres not a lot of work has been done on the tire physics. I was using the S2K car and I was understeering straight to the wall at 20MPH. It seems as if I was not using rubber tires (more like train wheel; just iron and no rubber).

I would also suggest to create a menu selection screen for tire selection (soft, hard & intermediate).

Brakes
The car seems to stop like it hit a wall as soon a you press the brakes. Even without ABS a car gradually slows down to a stop, a car will lock its brakes if it lost traction (eg; hit a smooth surface or water puddle).

Basically when I hit the brakes, the tires (which does not have any traction) just locks up and I go straight to the wall.

Acceleration/Traction control
Unless every car have an F1 engine in it. A 4 cylinder S2K will not peel out from 1000RPM. Peeling out (or lost of traction) is achived by bringing the RPM up high (like 5-7k rpm) and letting go of the clutch. In Drifting the principal is the same; at mid-drift the driver have to keep the RPM up to initiate a "Clutch Kick". On VDrift, as soon as I press the accelertor (even gradually) I start peeling out.

Graphics/Animation
Since this is development, I wont get into details, I am more into the physics of it rather than eye candy stylings.

VDRIFT definately have some potentials! I'll admit that. My only suggestions is adapt the acceleration, brakes and tire physics from Grand Tourismo4. So far it's the best one that I've seen.

Please do not take my opinion into offense. I am only trying to adapt reality into Virtual Reality.

PS: I have not successfully drifted with any of cars yet=) I think I need more practice on the controls.
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10-26-2006, 02:46 AM,
#2
 
Thanks for your input. No one will be offended by your opinion, in fact I'd have to agree with most of what you said.

First off, please try to find a joystick device (preferably a steering wheel) to try the game with, I think you'll find it much easier in many ways...next there are a few options that can make driving a little easier. Check out touchiness compensation in the menu under Options -> Controls -> Joystick Options.

While the default controls are keyboard ones, this does not mean they are the best. In fact all the non-analog controls are pretty bad because they are either 0% or 100%... This is an area that needs some work, we know. However it's not a very high priority...maybe it should be, people usually try it first and maybe it gives them a bad impression...

Anyway, aside from input, you're right about some of the cars. Many have problems of either over or under steering when they shouldn't at times. It is due in a large part to tire physics. VDrift simulates tire forces using the Pacejka "Magic Formula", as do many games. The only problem is that it's difficult to get good input variables for this formula for many different tires, and it's even more difficult, to tweak the values by guessing to get them right. There are some "Pacejka editors" out there but none that I'm able to use...so the short answer on the tires is that our tire system is acually quite good, but our data is very limited.

We did have a way in our old menu system to change the tires, as well as a few other things...getting that stuff back in the new menu system is in the todo.

As for brakes...using the keyboard pressing the brake is like in real life stamping your foot to get the pedal down to the floor as far as it will go as quickly as possible. In a normal car the brake has some resistance which works against your foot. But using the keyboard, or a mouse/joystick button, as the brake, will mean that the brake goes 100% down in 0 time. (This is certainly considered a bug in the controls...one we haven't figured out a great solution for yet.)

Acceleration: the problem is mostly tires. The cars use real life torque curves to determine how powerful the engines are. Again using keyboard or button controls it is totally unrealistic, like stomping the gas fully as fast as possible.

Adapting the physics behavior of a certain game or other is exceedingly difficult without specific knowledge of that game's source code. Also a big hurdle for us is the difficulty in obtaining specific detailed physical properties of cars (like Pacejka constants for tires).

Again I don't take offense to any of this, I feel the exact same way in many cases. The solutions to many of these problems would be found easily by another energetic open source developer with some free time and dedication to the project. VDrift's current dev team can find them in time, but we need help and patience...
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10-28-2006, 12:52 AM,
#3
 
VDrift's physics engine (which is the work of the Vamos developer Sam Varner) is more advanced than Gran Turismo 2, 3, and 4. I love the Gran Turismo games, but they do have some shortcomings in their physics engine... I'll prove it to you: in GT4, go get a lightweight supercar that's RWD, turbo it up to hundreds of horsepower, equip the tires with the least grip, turn off all driving aids (no TCS, no ABS), go to the parking lot, turn the wheel all the way to the left, and floor it in first gear. Instead of doing crazy donuts and swinging all over the place, your car just calmly and slowly turns in a nice circle. Even though the tires are squealing and smoking, the back end doesn't slip out. It really bugs me, and it's pretty much the reason I started the VDrift project. Gran Turismo does have better car data than we do, though, so their cars probably feel better most of the time, despite our cool physics engine.
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10-28-2006, 12:01 PM,
#4
 
The physics are actually really good in vDrift I think. In particular, I like the fact that the track surface being visibly smooth or rough affects the way the car handles - it basically does exactly what I expect it to do in most situations. There are only a very few problems I have with the physics, but I'm not going to poke any holes in it until I have some handle on how to go about helping fix it.
_____
Cotharyus
Remember: Horsepower is how hard you hit the wall. Torque is how far you take it with you.
http://cotharyus.net
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