rec.autos.simulators

But try sitting in your car and play with the "M" button...turning the
mirror on and off and more detail and less detail.  Ummm, from what I can
tell, the physics of what is happening around your car isn't changing at
all, but the frame rate sure is.

From my little experiments, the graphics are at least 50% of the FPS
equation in N4.  Which is good news, because it means there may be room for
optimisation.

Marc.

--
****************************************************************************
Marc Collins

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****************************************************************************

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

   What is the rate of the physics model in N4?  I know GPL is 288Hz
and would expect N4 to be the same (maybe faster, but probably not
considering the extra cars to be modeled, 43 vs. 20).  Also, with GPL
all cars use the same complex model, so I would assume the same is
true of N4 (for better or worse).

   So, 288Hz * 43 cars = 12,384 loops per second.  With a 1/1000sec
loop time, you're looking at "1238% Processor Occupancy" as the GPx
folks would put it.  Putt putt...

"But in a way, fear is a big part of racing, because if there was
nothing to be frightened of, and no limit, any fool could get into
a motor car and racing would not exist as a sport." -- Jim Clark

No, the AI uses a simplified model in GPL. I guess the same goes for
N4?

Andre

12000 loops/second isn't that much for today's CPUs. Yep, it really IS
fast, even though Windows seems to get slower and slower. ;-)

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/

But in Multiplayer, it can't fake it.  Wherever there is an accident there is a
player there, so it would make sense that if the physics were working on the
other end of the track in an accident involving another  online player,
wouldn't it then create a frame hit on my end?  I don't know, just asking.

Mike

Collisions don't have to take so much time; 2 OBB's colliding can be
done quite fast, and there are only 20 OBBs (except for the wheels) to
consider, so in the worst case you get 20*19 checks.
You can however get algorithms which start subdividing time when this
happens, which may lead to bad performance (in search for the
'perfect' collision time). However, I'd just do a check for a
reasonable hit point and sling away the cars to their new direction.

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/

  Not sure what it is.  Mine runs at 300Hz and takes 1/1000th second, so
multiply that by 43 and you've still got a good framerate.  I doubt the player
cars use the same physics.  It's so hard to program the AI to drive a model
like that I can't begin to describe it.  Human drivers have problems!  Granted,
N4's physics are probably a bit more intense than mine, but not *that much!*
:0P
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

  And don't forget to randomly "dynamite" some cars into low Earth orbit from
time to time :-)  Why don't folks use the relative velocities to calculate
collision impulses?  Seems like that would make these problems disappear.  
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

  Wow, that's a huge improvement.  Well, I've been wrong before, so...:-P
Perhaps the AI do run the same physics.  During the online races, are there AI
cars, or are there just player cars?  I don't have a copy of N4, so don't know
too much about it.
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

Ah yes, I've seen that happen, especially with the last version of
Racer on the net where the gravity was mistakingly converted to body
coordinates twice, resulting in something more like 'Spacer' ;-)
(it's fixed now, but still it can jump *higher* when falling to the
ground than the jump it originally came from; something with the
suspension I guess).

Hm, I did a pool program once, and it had (and has) the tendency to
have balls stick into eachother, since at the point of collision, the
bodies are inside eachother. Then, with some impulses, the balls get a
different velocity. But if the velocity is then not enough to untangle
the 2 balls, it collides again, and you get whacky planet-moon like
effects, with sinoidial effects you didn't remember putting in! ;-)
The problem gets worse when 3 cars collide at the same time, I think.
They just have to stay away from eachother, somehow. Gosh, hm,
collision detection, more to read.

PS How's the Straightline Acceleration Simulation sales going? Too bad
you don't accept credit cards.

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/

  Hehe!  I'd love to try Racer, but my P-60 won't handle it, and I can't
currently plug my wheel into my P-400 laptop, so I'm out either way.  Unless
you can whip up a keyboard steering mode! :-)

  >(it's fixed now, but still it can jump *higher* when falling to the

  Mine usually doesn't do that, but then again, as soon as it gets upside down
and lands, it'll shoot past the moon in a real hurry! (no collision detection
yet)  

  Hadn't thought of that.  I knew it wouldn't be so simple :-)

  Not too bad.  Had a few orders during the two week sale.  Only about half of
the emailers actually sent checks though!  lol  I'll reset the price and if
there's enough response, get signed up with one of those Delaware based online
credit card deals.  I must say, version two of the program will be outrageous
in comparison, given all I've learned during the past 10 months or so of
development with the 3-D dynamics.  There aren't a whole lot of competitors
that offer spring and damper adjustments and all the other bells and whistles
to the drag car predictors.  It's pretty cool seeing a 7 second car pull the
front wheels in 3-D, with the tires spinning crazily off the line:-)  Adjusting
the shocks to 90/10 drag types gives the right reaction now too, so perhaps SAS
Pro could be in the works soon.  Either that or I'll dive back into engine
simulation and get something really nice going in that dept.  Seems I get more
hits from search engines looking for "engine dyno simulators" than "drag
simulators" anyway.  Decisions, decisions... ;-)  

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com