rec.autos.simulators

Hi folks. I mailed MPS UK about WC2 and friends. I wanted to know
principally if there would be any proper networking in GP2. Here's the
response:

Doom and GP2/ICR2/Nascar are two differnt things.  In Doom you don't depend
on quite as many refreshes per second (I know, I've looked at the code).  
You aren't quite as dead in Doom if your refresh doesn't happen.  There is
a lot more update and a lot more movement per frame in the racing sims.  As
somebody pointed out, at Indy you move more than a football field in a second.
at 15 frame per second, that's 20 feet.  In Doom, only the bullets go that fast.
Opponents don't go anywhere near that speed.  F1 speeds are slightly lower
than Indy, but the point remains.

On the other hand, I don't agree with the packetizing statement on a general
basis.  Network speeds are very high compared to modem speeds.  A ***y fast
modem is 115kbaud, which 14.7 _kilo_Bbytes/sec.  A SLOW network is ethernet,
which is 10 Mbits/sec, or 1.2 _mega_Bytes/sec.  Even if you wait for a whole
packet, you're still able to go fast.  (And wait for FastEthernet, at 100 Mbit)
The problem is with all of the other software that goes around it, and how
busy the network is.

And it *is* possible to do near-real-time network communications.  You just
can't do it over a busy network.

--

Brian Wong                              Product Marketing Engineering

Hmm, thats funny, I could have sworn I played a little game about 18 months
ago called Doom which seemed to have no trouble doing just that...

2 player modem play will do me fine however, as long as it works.

/      \
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"it won't happen overnight, but it will happen." -Rachel Hunter.

I think the reason Doom works fine and F1GP 2 doesn't is that Doom isn't as
time critical as F1GP in getting the situation from other computers.

If, for example, there is a 1/10 second delay in the transfer between
computers, that won't matter in a game like Doom. On the other hand, a formula
one car doing 300 km/h (185mph) will move about 8m (27ft) in that time. That
kind of delay makes it quite difficult to drive close to another car, as it
might cause problems like in your computer it seems like you've completed a
pass, but in the other computer the cars are still side by side.

Note that I pulled the 1/10 second out of a hat, but I think it is quite close
to a delay caused by a network (correct me on this if I am wrong).

Samppa
--

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If you have 100 millisecond delay you're on a very slow network.  100 ms
is a WHOLE lot of bit times, even on ethernet...
--

Brian Wong                              Product Marketing Engineering

The amount of data needed to transfer for one car is probably something
like 8 bytes for position (4 bytes x, 4 bytes y), 2 bytes for heading,
2 bytes for engine rpm (to generate correct sounds), 2 bytes for speed and
maybe 2-4 bytes for other information. Now, speed could probably be dropped
out or maybe transferred about once a second, as can engine rpm. That still
leaves 14-16 bytes for each frame. Also, one master computer must collect the
data from the other players computers, combine them, and send out data for all
26 cars on the track.
Now, for the game, it is necessary to:
1) all other players send their 16 byte packets to the master.
2) the master has to combine the data and possibly handle collisions.
3) the master must now send 26*16 = 416 bytes to each of the other players.
4) each computer must calculate the screen for the players.
These four steps must happen about 20 times per second for the game to run
smoothly. Also, there must be time to simulate the player cars, and handle
the AI cars. This will total to about 10kb per second.

Will a network respond rapidly enough to allow the computers a reasonable time
to calculate the screen? (I'm not trying to convince that a network wouldn't
be fast enough. I only have had experience with ftp through a network, and
have reached transfer rates of few hundred kbytes per second, which would
indicate there shouldn't be any problems).
The 100 microseconds I used in my previous post came from the assumption that
the network doesn't respond immediately, but there is a slight delay.

If you Brian or somebody else know that a network (ethernet) can handle the
data fast enough, I don't see any reason not to include network support in
F1GP 2. Maybe they're just too lazy to develop the routines for network (but
if they already have serial line 2 player support, this wouldn't cause too
much work, would it?).

Samppa
--

| Kannaksenkatu 13 |----------------------------------------------------------|
|     40600 JKL    |            Check out the NHSound homepage at             |
|      FINLAND     |          http://www.jyu.fi/~tamasa/nhsound.html          |

: If you Brian or somebody else know that a network (ethernet) can handle the
: data fast enough, I don't see any reason not to include network support in
: F1GP 2.

All you need to do is look at the game X-Pilot.  This is a true network
game that plays pretty good if you are in a LOCAL network.  It plays very
nicely when using 8 players and about 3 robots.  Anyway, I haven't tried
it cross-country so I can't say what that would do.  I have heard it has
lag, but that's top be expected.

The reason I use X-Pilot as an example is because it is a frame-rate
intensive game, ie the better the frame rate the easier it is to fly.  
Any lag is an immediate trip into the wall when your terminal 'catches
up'.

What they COULD do is like <choke> Papyrus.  That is to have a local
'host' that people call into and race over the modem.  The 'host' takes
care of everything.  This isn't out yet either, but should be soon.