Tribes 2 wheeled vehicles - what is the real story?
by Wes Nelson · in Torque Game Engine · 04/09/2001 (8:41 am) · 15 replies
Just after Tribes 2 was announced there were some screenshots featuring wheeled ground vehicles. I even remember some employee .plan updates journaling the work on vehicle physics and how cool they'd be.
Only one wheeled vehicle actually ended up in the game; the Mobile Point Base. For those who havn't played the game, the Mobile Point Base is a huge, six-wheeled behemoth that features a rocket turret and a full-featured inventory station. It's slow and lumbering, and quite difficult to drive since it also tends to skid around quite a bit (which seems "wrong" given its size and weight), and don't even drive near a valley or you'll be standing at the bottom with fiery wreckage raining on you.
This weekend I cracked open the script file which contains all the physical properties of the MPB and, for the fun of it, doubled the engine power to see if I could get that thing moving a little faster for some "off-road" fun.
Boy was I suprised when I hit the first bump and the vehicle simply started flipping in space. (No, it didn't jump into the air and start flipping, it just started spinning like crazy, dipping into the terrain). A few seconds later the MPB fell through the terrain off into space. Continued experimentation with new physical properties and driving techniques produced similar (insane) results.
Here is my question:
Were the other wheeled vehicles removed and replaced with "easier" hovering vehicles because the wheeled vehicle physics were not working right?
I'm simply curious if wheeled ground vehicles are going to be a possible sticking point for V12 developers.
Thanks!
Only one wheeled vehicle actually ended up in the game; the Mobile Point Base. For those who havn't played the game, the Mobile Point Base is a huge, six-wheeled behemoth that features a rocket turret and a full-featured inventory station. It's slow and lumbering, and quite difficult to drive since it also tends to skid around quite a bit (which seems "wrong" given its size and weight), and don't even drive near a valley or you'll be standing at the bottom with fiery wreckage raining on you.
This weekend I cracked open the script file which contains all the physical properties of the MPB and, for the fun of it, doubled the engine power to see if I could get that thing moving a little faster for some "off-road" fun.
Boy was I suprised when I hit the first bump and the vehicle simply started flipping in space. (No, it didn't jump into the air and start flipping, it just started spinning like crazy, dipping into the terrain). A few seconds later the MPB fell through the terrain off into space. Continued experimentation with new physical properties and driving techniques produced similar (insane) results.
Here is my question:
Were the other wheeled vehicles removed and replaced with "easier" hovering vehicles because the wheeled vehicle physics were not working right?
I'm simply curious if wheeled ground vehicles are going to be a possible sticking point for V12 developers.
Thanks!
#2
As for your tank... It's probably a problem with one of the spring force or damping settings. The spring forces are very sensitive to hysteresis effects during integration and can spiral out of control when large forces are applied. To make matters worse, Dynamix reduced the wheel integration rate down to 30 Hz (I had them running at 120 Hz, and I know the Papyrus guys Nascar 4 etc. run their cars at 300 Hz). This is going to make it very tough, if not impossible to make high speed ground vehicles with T2 mods.
04/09/2001 (10:16 am)
I was the one working on the vehicle physics and network prediction. I thought they were working pretty well and the small scout vehicle was a blast to drive around. When I left they were about 90% done, there were a few remaining issues: the static tire load calculation was a total hack (I wasn't really clear on how that should be calculated), the new collision code had to be integrated, and testing wheels with the terrain and interiors was a little expensive. I haven't gotten the whole picture on why they decided to remove them, but I believe it basically came to the crunch and they didn't have the time or personnel to mess with it. I guess it was easier to simply add some hover code than tweak, optimize and balance the ground vehicles. I drove the hover scout around the other day and think it's lame compared to what the wheeled one was like, oh well.As for your tank... It's probably a problem with one of the spring force or damping settings. The spring forces are very sensitive to hysteresis effects during integration and can spiral out of control when large forces are applied. To make matters worse, Dynamix reduced the wheel integration rate down to 30 Hz (I had them running at 120 Hz, and I know the Papyrus guys Nascar 4 etc. run their cars at 300 Hz). This is going to make it very tough, if not impossible to make high speed ground vehicles with T2 mods.
#3
You're absolutely right... driving around in a fast vehicle is tons of fun. I readjusted the spring properties as you suggested and I was able to keep things from freaking out. But like you said... once you get going fast all hell breaks loose. The time up until the "superfast mpb" hits a bump and explodes is great! I love watching the wheels absorb small bumps and rebound. Great job!
So if a V12 developer bumps the integration rate back up to 120hz, is the quadrupled number of tire traces going to be the prohibiting factor on performance? Do you think hacks like doing traces for half of the tires 1 integration frame, and the rest the next would produce quality results? (This seems like it would work particularly well with 6 wheeled vehicles, since there would always be 3 traces per frame).
04/09/2001 (11:27 am)
It's too bad really.You're absolutely right... driving around in a fast vehicle is tons of fun. I readjusted the spring properties as you suggested and I was able to keep things from freaking out. But like you said... once you get going fast all hell breaks loose. The time up until the "superfast mpb" hits a bump and explodes is great! I love watching the wheels absorb small bumps and rebound. Great job!
So if a V12 developer bumps the integration rate back up to 120hz, is the quadrupled number of tire traces going to be the prohibiting factor on performance? Do you think hacks like doing traces for half of the tires 1 integration frame, and the rest the next would produce quality results? (This seems like it would work particularly well with 6 wheeled vehicles, since there would always be 3 traces per frame).
#4
Eric Wright
Programmer
Black Hole Productions
http://www.bhpro.com
04/09/2001 (11:30 am)
Thats very intersting, i'm glad you posted it gave me some ideas for my dev teams game :).Eric Wright
Programmer
Black Hole Productions
http://www.bhpro.com
#5
04/09/2001 (6:17 pm)
Wes, I actually had the collision separated out. Collision test ran at 32 Hz which is the standard for all objects (I said 30 earlier, but it's actually 32), and the rest, which included the suspension, engine torque, tire traction etc., ran at 120 Hz. This seemed to produce pretty good results and I'm not quite sure why they reduced it back down to 32. The expensive part was testing the wheel and body collisions (more than 5 time the work of a normal player) and not the wheel physics. I get the feeling that wheeled vehicles were showing up high in one of the profiles and they simply cut back on everything they could find. It's too bad they didn't make the integration rate a vehicle script parameter.
#6
It was one of the more popular vehicles at E3 last year. I myself spent a good amount of the time I had playing around with the bike.
The hover scout has it's charm on the water maps. But the missing wheeled scoutbike was a dis-appointment.
But the GUI editor and new GUI setup has kept me a bit busy over the weekends
04/09/2001 (7:46 pm)
I myself was very disappointed with the removal of the 4-wheel atv scout bike.It was one of the more popular vehicles at E3 last year. I myself spent a good amount of the time I had playing around with the bike.
The hover scout has it's charm on the water maps. But the missing wheeled scoutbike was a dis-appointment.
But the GUI editor and new GUI setup has kept me a bit busy over the weekends
#7
05/18/2001 (10:32 am)
Maybe as a possible bonus the "wheel" code could be optimized or fixed as needed and released as a patch for the code after the initial V12 code release.
#8
05/19/2001 (9:46 am)
I'm sure we'll get plenty of people playing with the vehicle code :) Fixing the wheel integration rate will be easy, but I'm sure there are a number of other things that could be done to improve both the efficiency and the behavior of the physics.
#9
05/20/2001 (9:48 am)
I'd like to know if this could be used in other ways, such as watercrafts and other non wheel based vehicles, or what is supported for vehicles like those (general vehicles on any terrain).
#10
oh well thats how development goes :(
maybe they could come back in a tribes2 addon :)
05/20/2001 (7:22 pm)
Yeah i was really looking forward to wheeled vehicles in tribes2! i didnt even know they were scrapped untill i actually loaded the game up.oh well thats how development goes :(
maybe they could come back in a tribes2 addon :)
#11
07/10/2001 (11:25 am)
My group has been working on a mod, and the vehicle code is a sticking point for us. I had talked to Dave about the ATV being removed, and was told because the screen jiggled to much when riding it, and people had a bad case of getting motion sick. I was able to talk to him within a week of their announcement that the ATV was being yanked, and replaced by the wildcat.
#12
I really think someone screwed up the Wheeled vehicle code at somepoint.. AFTER it had been perfected. I tried the ATV at E3 when they showed T2 last year.. The system didn't seem to jitter to me (unlike trying to drive tha MPB now).
The hoverbike jitters worse then the ATV did ;(
07/10/2001 (2:30 pm)
What ATV did he ride?I really think someone screwed up the Wheeled vehicle code at somepoint.. AFTER it had been perfected. I tried the ATV at E3 when they showed T2 last year.. The system didn't seem to jitter to me (unlike trying to drive tha MPB now).
The hoverbike jitters worse then the ATV did ;(
#13
07/10/2001 (6:12 pm)
I agree, and of course, that happened after I left :) I haven't had a chance to look at the vehicle code recently, so besides the reduction in the integration rate, I'm not sure what else they've changed. Since everyone will have access to the code shortly, I'm sure we'll get it sorted out. At least for V12 users and mods. The T2 mod's are basically hosed.
#14
> torque, tire traction etc., ran at 120 Hz. This
> seemed to produce pretty good results and I'm not
> quite sure why they reduced it back down to 32.
I wonder if this change is related to the mysterious "loop-less loop" in Vehicle::processTick:
Maybe this used to have a loop bound of 4, with arguments of TickSec/4.0 for the subroutine calls.
02/02/2002 (9:40 pm)
> the rest, which included the suspension, engine> torque, tire traction etc., ran at 120 Hz. This
> seemed to produce pretty good results and I'm not
> quite sure why they reduced it back down to 32.
I wonder if this change is related to the mysterious "loop-less loop" in Vehicle::processTick:
for (U32 i = 0; i < 1; i++) {
mRigid.clearForces();
updateForces(TickSec);
updatePos(TickSec);
}Maybe this used to have a loop bound of 4, with arguments of TickSec/4.0 for the subroutine calls.
Simon Sancartier
I think the wheeled vehicles themselves have been removed because they were difficult to tune and tweak and probably also because they didn't feel it necessary for them to be absolutely wheeled. If you ask me, I find the Beowulf much more cooler in it's turbo-grav version than it could be if wheeled.
They probably just felt the game wouldn't suffer from not having them be wheeled vehicles, and that's what design is... making sacrifices.
If you don't mind putting time into coding them, I don't think wheeled vehicles will be a problem. Depending on the game, it might be better to have wheeled vehicles if your game is set in the 20th-21st century... but Tribes is set in the 40th century so they can pretty much make you believe whatever they want. ;)