Lanzfeld Posted January 27, 2000 Share Posted January 27, 2000 One of the things I really like about CM is the way the game models the acceleration of the tanks, however, it seems that it deos not model the stopping distance. The Hellcats will tear-ass down the road at upwards of 50 mph then come to an instant stop! Am I wrong or has this been addressed? Link to comment Share on other sites More sharing options...
Major Tom Posted January 27, 2000 Share Posted January 27, 2000 I am pretty sure that all tracked vehicles have darned good traction, enough that they can probably stop on a dime. Link to comment Share on other sites More sharing options...
Goanna Posted January 27, 2000 Share Posted January 27, 2000 Major Tom is referring to the fact that they have a large surface area of contact with the ground since the force of friction that will be allowable to stop the tank is equal to the force of gravity, the surface area of ground touching tracks, and the coefficient of friction between the tracks and surface of the earth. Provided that these all add up to a lot of stopping force (they do) the limiting factor would then become internal stress limits in the drive wheels, drive trains and gears in the vehicle. I can imagine there were a number of breakdowns in trying to stop Tigers or other heavy tanks on dry surfaces too quickly. It would also be possible to skid a tank pretty easily on mud, wet or icy surfaces (and would make some cool video). ------------------ desert rat wannabe Link to comment Share on other sites More sharing options...
Guest Zigster Posted January 27, 2000 Share Posted January 27, 2000 Saw a great pic of a tank that slid off an icy corner and into a ditch. Link to comment Share on other sites More sharing options...
Major Tom Posted January 27, 2000 Share Posted January 27, 2000 Exactly, the coefficient of the surface gravity area against the force of friction on the angle of the thing with the other stuff... Um, Yeah, Goanna, your StuG's are going to be doing a lot of this sudden stopping and fleeing for their petty lives in our PBEM! I hope your poor little Stuggies don't have any engine failure! [This message has been edited by Major Tom (edited 01-27-2000).] Link to comment Share on other sites More sharing options...
Mattias Posted January 27, 2000 Share Posted January 27, 2000 All physics in the world aside, it is a game mechanical concession. Above all, calculating deceleration causes some quite complicated and processor intensive problems for the AI. In the end it was left out. It has been discussed in detail earlier so no need to argue really. M. Link to comment Share on other sites More sharing options...
Fionn Posted January 27, 2000 Share Posted January 27, 2000 Actually vehicles DO stop on a dime in CM simply because if they didn't then the AI would need to figure out where to start braking to come to a stop at a specific point and that would require REALLY intense AI calculations and mean a noticeable performance degradation. Therefore it was simply assumed that vehicles can come to a complete stop instantly. it's not 100% correct of course but if you assume they applied brakes a bit earlier so as to come to a stop in that point it makes a lot more sense.. Not 100% accurate but CM is a wargame and not a driving physics simulator ... Still, if it wasn't so difficult for the AI to handle I'm sure it'd be in. ------------------ ___________ Fionn Kelly Manager of Historical Research, The Gamers Net - Gaming for Gamers Link to comment Share on other sites More sharing options...
Doug Beman Posted January 27, 2000 Share Posted January 27, 2000 Yeah, that makes sense. If they need to stop at point X, what does it matter if you can see their brake lights flash at the correct distance before X, or if they just roar up to x-1 meter and then drive the brake pedal into the floor? Now, we just need some code so that tanks stopping on pavement will go SCREEEEEECCHHHH and leave big black streaks on the road surface. DjB ps: ever wonder why it is that, in a movie scene where a car stops quickly, there will ALWAYS be a locked-brakes SCREECH even if the car has ABS? Link to comment Share on other sites More sharing options...
Das Boot Posted January 27, 2000 Share Posted January 27, 2000 Yeah Doug, that's right. On the same note, why is it, that even when driving down a perfectly straight road it's necessary to turn the steering wheel vigorously from side to side every few moments? Or that you can always park directly outside the building you're visiting? ------------------ The first casualty when war comes is truth Link to comment Share on other sites More sharing options...
Guest Madmatt Posted January 27, 2000 Share Posted January 27, 2000 Yes, this same question was asked a few months back by a mere junior member then, name of Madmatt...I remember it clearly...All excited that I had a question worthy of posting, scared of the flames that might ensue, patiently waiting to see if (the then) legendary Fionn or Moon or even (GASP) the great one himself, STEVE would respond....Ahhh the joy , the pain of waiting I couldn't contain my enthusiasm Ok ok ok, here is what Steve said about it almost 2 months ago...: <BLOCKQUOTE>quote:</font><HR>Matt, The scaling does make it seem more extreme than it is, but we don't have deceleration. Would LOVE to have it, but found that the Tac/Strat AIs required far too many CPU cycles to anticipate it correctly. Since the AIs couldn't be coded to use it correctly, and is really only an issue for fast moving vehicles, we decided it was better to just leave it out. Realistic? Nope. Could we get both realism and gameplay to work together on this? Sadly, no. <HR></BLOCKQUOTE> And thats why...I had also asked if they could model tanks 'locking tracks' and skidding, but it appears that was also a little too much to model...Probably just throw a tread evertime I did that anyway! Madmatt out... ------------------ If it's in Combat Mission, it's on Combat Mission HQ! combathq.thegamers.net [This message has been edited by Madmatt (edited 01-27-2000).] Link to comment Share on other sites More sharing options...
Guest Big Time Software Posted January 27, 2000 Share Posted January 27, 2000 Just to finish this one up... A tank could stop on a dime (or almost) if it were going at Move or Hunt speeds. Fast... well... depends on the vehicle in question. A Churchill or Jagdtiger can't go that fast, so their braking time would not be all that great. Maybe 10m or so?? Wheeled vehicles on pavement going fast would take more than that, but since they usually get picked off as their means of stopping, not a big deal The single worst case combo is a Hellcat going Fast on paved road. The Hellcat can go almost twice as fast as most tanks, and significantly faster than the rest. So we feel at least comfortable with the suspension of reality in regards to braking becaue the Hellcat in SOME circumstances is basically the only one that REALLY breaks the rules of reality to a noticable degree. Steve Link to comment Share on other sites More sharing options...
Aacooper Posted January 27, 2000 Share Posted January 27, 2000 Here´s a braking equation: v(t)=v0-at d=v0^2/(2a) It wouldn´t tax the processor! But I agree with BTS. Link to comment Share on other sites More sharing options...
Scott C Posted January 27, 2000 Share Posted January 27, 2000 Unfortunately it isn't that simple, since the frictional force is proportional to the velocity (assuming that the object is in fact moving... if not, a different kind of friction, static friction, comes into play). Thus the situation actually is: a=-mass*gravity*friction coefficient*velocity and thus velocity goes as a negative exponential, which is substantially more computationally intensive. And then if you start to factor in such things as air resistance, losses in the drive train, etc., it gets even worse... but this first-order approximation is already pretty bad. Sorry to run on like this - occupational hazard of being a physicist, I suppose. ------------------ Questions, comments, arguments, refutations, criticisms, and/or sea stories? Link to comment Share on other sites More sharing options...
DesertFox Posted January 28, 2000 Share Posted January 28, 2000 Hehehe Interesting discussion I say a tank stops nearly on a dime. Max 5 metres from 50km/h to zero on a asphalt street and 2-3 metres on a field. But don´t ask how the street looks like afterwards Helge ============== Sbelling chequed wyth MICROSOFT SPELLCHECKER - vorgs grate! - The DesertFox - Email: desertfox1891@hotmail.com WWW: http://www.geocities.com/Area51/Capsule/2930/ Link to comment Share on other sites More sharing options...
Aacooper Posted January 28, 2000 Share Posted January 28, 2000 Scott C, speaking as an engineer, you have to have assumptions, and these were the ones I used: v0 = initial velocity a = constant acceleration (this can be averaged over the stopping distance) The biggest variables for acceleration are probably the ground conditions, because it´s pretty safe to assume all WW2-era tanks will have similar braking performance. Link to comment Share on other sites More sharing options...
Guest Sgt Morgue Posted January 28, 2000 Share Posted January 28, 2000 in my experince with the M48 and M60 tanks stop from their top end of 32mph faster than the crew , so the driver would only jam the brakes in an emergency. i am sure the same holds true for the faster M80 (M1)tank. But the speed of the stop in the game is mox-nix, this is a great game!!! Link to comment Share on other sites More sharing options...
Goanna Posted January 28, 2000 Share Posted January 28, 2000 Scott C, I hate to disagree with a physicist, but I have to in this case. In fact, unless the vehicle is in a skid, the static coefficient of friction will be used for a braking vehicle since the tread is not in motion at its point of contact with the road. Only when a vehicle starts to skid is the much lower dynamic coefficient of friction used (which is proportional to velocity as you stated). The modelling difficulties I suspect have more to do with accurately modelling the deceleration of the heavy vehicles so the velocities are accurately displayed over time. But how I would dearly love to see the movie of 200 m of tarmac rolled up under a M18 stopping from top speed on a clean dry paved road. Goanna - CPEng ------------------ desert rat wannabe Link to comment Share on other sites More sharing options...
Doug Beman Posted January 28, 2000 Share Posted January 28, 2000 Das Boot, if you wanna see a really funny take on the "twist the wheel willynilly" theme, check out the scene from "Airplane" wherein Robert Stack drives Lloyd Bridges to the airport. Everytime I watch that I just about wet myself. DjB Link to comment Share on other sites More sharing options...
Scott C Posted January 28, 2000 Share Posted January 28, 2000 Goanna: Quite true. I did not type that in because it was already getting too long. My understanding, however, was that WWII tanks did actually lock their treads and skid when they wanted to stop quickly - something about not having any way to apply brakes directly to the tread, if my officemate told me correctly. (my non-grognardness may be showing here) If this is not the case, I need to go pound somebody over the head for giving me bad information since I don't like finding out I'm wrong. Aacooper: Averaging the a over the distance creates a whole slew of extra problems. The only way to get an average a that holds for stopping from a slow move and for a fast move is to actually do the exponetial calculation. Some "typical" value can be selected in several ways, but will generally be grossly inaccurate for some regimes. It's also the sort of ad-hoc method I dislike using in my own work, something that gives a result that kind of looks right but isn't. Call me crazy, but I find stopping on a dime a good deal less bothersome than assuming a constant deceleration (unless as Goanna implies, the tank actually isn't in a skid, in which case it's fine). ------------------ Questions, comments, arguments, refutations, criticisms, and/or sea stories? Link to comment Share on other sites More sharing options...
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