Login name: johnc In real life: John Carmack
Directory: /raid/nardo/johnc Shell: /bin/bash
Last login Fri Aug 16 12:36 on ttyp2 from idnewt
Here is The New Plan:
I copied off the quake codebase and set about doing some major improvements.
The old v1.01 codebase will still be updated to fix bugs with the current
version, but I didn't want to hold back from fixing things properly even if
it involves some major changes.
I am focusing on the internet play aspect of the game. While I can lay out
a grand clean-sheet-of-paper design, I have chosen to pursue something of a
limited enough scope that I can expect to start testing it around the end
of the month (august). I still have my grand plans for the future, but I
want to get some stuff going NOW.
The code I am developing right now is EXCLUSIVELY for internet play. It
will be rolled back into the single player game sometime along the road
to Quake 2 (or whatever it turns out to be called), but the experimental
QuakeWorld release will consist of seperate programs for the client and
the server. They will use the same data as the current registered quake,
so the only thing that will be distributed is new executables (they will
peacefully coexist with current quake).
There will be a single master server running here at id. Whenever anyone
starts up a server, it will register itself with the master server, and
whenever a client wants to start a game, it will inquire with the master
to find out which servers are available.
Users will have a persistant account, and all frags on the entire internet
will be logged. I want us to be able to give a global ranking order of
everyone playing the game. You should be able to say, "I am one of the
ten best QuakeWorld players in existance", and have the record to back it
up. There are all sorts of other cool stats that we could mine out of
the data: greatest frags/minute, longest uninterrupted quake game,
cruelest to newbies, etc, etc.
For the time being, this is just my pet research project. The new exes
will only work with registered Quake, so I can justify it as a registration
incentive (don't pirate!).
If it looks feasable, I would like to see internet focused gaming become
a justifiable biz direction for us. Its definately cool, but it is
uncertain if people can actually make money at it. My halfway thought
out proposal for a biz plan is that we let anyone play the game as an
anonymous newbie to see if they like it, but to get their name registered
and get on the ranking list, they need to pay $10 or so. Newbies would
be automatically kicked from servers if a paying customer wants to get on.
The game physics is being reworked to make it faster and more uniform.
Currently, a p90 dedicated server is about 50% loaded with eight players.
The new network code causes a higher cpu load, so I am trying to at least
overbalance that, and maybe make a little headway. A single p6-200 system
should be able to run around ten simultanious eight player servers.
Multiple servers running on a single machine will work a lot better with
the master server automatically dealing with different port adresses
behind the client's back.
A couple subtle features are actually going away. The automatic view
tilting on slopes and stairs is buggy in v1.01, and over a couple hundred
millisecond latancy connection, it doesn't usually start tilting until you
are allready on a different surface, so I just ripped it out entirely.
A few other non-crucial game behaviors are also being cut in the interest
of making the physics easier to match on the client side.
I'm going to do a good chat mode.
Servers will have good access control lists. If somebody manages to piss
off the entire community, we could even ban them at the master server.
The big difference is in the net code. While I can remember and justify
all of my decisions about networking from DOOM through Quake, the bottom
line is that I was working with the wrong basic assumptions for doing a
good internet game. My original design was targeted at <200ms connection
latencies. People that have a digital connection to the internet through
a good provider get a pretty good game experience. Unfortunately, 99% of
the world gets on with a slip or ppp connection over a modem, often through
a crappy overcrowded ISP. This gives 300+ ms latencies, minimum. Client.
User's modem. ISP's modem. Server. ISP's modem. User's modem. Client.
God, that sucks.
Ok, I made a bad call. I have a T1 to my house, so I just wasn't familliar
with PPP life. I'm adressing it now.
The first move was to scrap the current net code. It was based on a
reliable stream as its original primitive (way back in qtest), then was
retrofited to have an unreliable sideband to make internet play feasable.
It was a big mess, so I took it out and shot it. The new code has the
unreliable packet as its basic primitive, and all the complexities that
entails is now visible to the main code instead of hidden under the net api.
This is A Good Thing. Goodbye phantom unconnected players, messages not
getting through, etc.
The next move was a straightforward attack on latency. The communications
channel is not the only thing that contributes to a latent response, and
there was some good ground to improve on.
In a perfect environment, the instant you provided any input (pressed a
key, moved a mouse, etc) you would have feedback on the screen (or speaker)
from the action.
In the real world, even single player games have latency.
A typical game loop goes something like: Read user input. Simulate the
world. Render a new graphics scene. Repeat.
If the game is running 15 frames a second, that is 66 ms each frame. The
user input will arive at a random point in the frame, so it will be an
average of 33 ms before the input is even looked at. The input is then
read, and 66 more ms pass before the result is actually displayed to the
user, for a total of nearly 100 ms of latency, right on your desktop.
(you can even count another 8 ms or so for raster refresh if you want to
The best way to adress that latency is to just make the game run faster if
possible. If the screen was sized down so that the game ran 25 fps, the
latency would be down to 60ms. There are a few other things that can be
done to shave a bit more off, like short circuiting some late braeking
information (like view angles) directly into the refresh stage, bypassing
the simulation stage.
The bearing that this all has on net play, aside from setting an upper
limit on performance, is that the current Quake servers have a similar
frame cycle. They had to, to provide -listen server support. Even when
you run a dedicated server, the model is still: fetch all input, process
the world, send updates out to all clients. The default server framerate
is 20 fps (50 ms). You can change this by adjusting the sys_ticrate cvar,
but there are problems either way. If you ask for more fps from the server,
you may get less latency, but you would almost certainly overcommit the
bandwidth of a dialup link, resulting in all sorts of unwanted buffering
in the routers and huge multi thousand ms latency times as things unclog
(if they ever do).
The proper way to address this is by changing the server model from a
game style loop to a fileserver/database style loop.
Instead of expecting everyone's messages to be dealt with at once, I now
deal with each packet as it comes in. That player alone is moved forward
in time, and a custom response is sent out in very short order. The rest
of the objects in the world are spread out between the incoming packets.
There are a lot of issues that that brings up. Time is no longer advancing
uniformly for all objects in the world, which can cause a lot of problems.
It works, though! The average time from a packet ariving at the system to
the time a response is sent back is down to under 4ms, as opposed to over
50 with the old dedicated servers.
Another side benefit is that the server never blindly sends packets out
into the void, they must be specifically asked for (note that this is
NOT a strict request/reply, because the client is streaming request
without waiting for the replies).
I am going to be adding bandwidth estimation to help out modem links.
If quake knows that a link is clogged up, it can choose not to send
anything else, which is far, far better than letting the network buffer
everything up or randomly drop packets. A dialup line can just say
"never send more than 2000 bytes a second in datagrams", and while the
update rate may drop in an overcommited situation, the latency will
never pile up like it can with the current version of quake.
The biggest difference is the addition of client side movement simulation.
I am now allowing the client to guess at the results of the users movement
until the authoritative response from the server comes through. This is a
biiiig architectural change. The client now needs to know about solidity
of objects, friction, gravity, etc. I am sad to see the elegent
client-as-terminal setup go away, but I am practical above idealistic.
The server is still the final word, so the client is allways repredicting
it's movement based off of the last known good message from the server.
There are still a lot of things I need to work out, but the basic results
are as hoped for: even playing over a 200+ ms latency link, the player
movement feels exactly like you are playing a single player game (under
the right circumstances -- you can also get it to act rather weird at
The latency isn't gone, though. The client doesn't simulate other objects
in the world, so you apear to run a lot closer to doors before they open,
and most noticably, projectiles from your weapons seem to come out from
where you were, instead of where you are, if you are strafing sideways
while you shoot.
An interesting issue to watch when this gets out is that you won't be
able to tell how long the latency to the server is based on your movement,
but you will need to lead your opponents differently when shooting at them.
In a clean sheet of paper redesign, I would try to correct more of the
discrepencies, but I think I am going to have a big enough improvement
coming out of my current work to make a lot of people very happy.
Romero is now gone from id.
There will be no more grandiose statements about our future projects.
I can tell you what I am thinking, and what I am trying to acomplish,
but all I promise is my best effort.
QuakeWorld structural addendum:
After hearing many arguments against the single master server, ranging
from coherent and well reasoned to paranoid whining, I now agree that
the single global master server isn't sufficient.
During the R&D phase, there will still be only the single server, but
after all the kinks get worked out, I will allow a small number of
sites to run private master servers. This will not be a general
release, but only to properly licensed third parties. That will still
allow me to collect my 100% coverage data, and it will prevent a
single network/computer/software failure from preventing all QuakeWorld
QuakeWorld technical addendum:
I am reining in the client side prediction to a fairly minimal amount.
It has too many negative effects in different circumstances. The problem
of running away from or in front of your missiles was so bad that I
considered simulating the missiles on the client side, but that is the
second step on a slippery slope. If just the missiles were simulated,
then a missile would fire through an enemy until the server informed
you it exploded on them. Then you consider simulating interactions,
but then you have to guess at other player inputs (which is hopeless)...
Lesson learned: Simulating 300 ms on the client side in a Quake style
game is just out of the question. It probably works fine for flight sim
or driving sims, but not in out twitch reaction games.
I am currently using client side simulation to smooth out the beat
frequency interactions between server packet arrival and client frame
times. In the shipping version of Quake, some latency was introduced
on purpose to keep the displayed frame simulation time between the last
two packets from the server so that the variability in arrival time
could be smoothed out. In QuakeWorld, I am always starting with the
most current packet, and using simulation to smooth out the variability.
This <100ms of client side motion seems to be very manageable, and cuts
out some real latency as well as doing the gueswork.
It looks like I am going to split the QuakeWorld client into multiple
threads to reduce the avg 1/2 frame latency between input and packet
sending. This is also a step towards building a multi-threaded Quake
renderer, which will let multi-cpu NT machines render twice as fast.
Lets hope the windows thread scheduler is decent...
I have been cutting down the message sizes a bit here and there as
well. On a modem link, every couple bytes I save translates into a
millisecond of latency saved. I cut an average of 17 bytes from the
server to client and 8 from the client to server today.
Apogee's Prey team (and Duke's Levelord) leave 3drealms to work
with Quake technology as Hipnotic Interactive.
I am considering increasing the default sv_friction value for
QuakeWorld from 4 to 6 or 8.
It might take a little getting used to, but I think it gives more
precise control for wide area network play.
If anyone wants to run some experiments with different friction
levels on a current Quake server, I would be interested in hearing
The remote server console commands are fully implemented for
To allow remote administration, the server must set the "password"
cvar. By default, remote administration is turned off.
On a client, if you set the "password" cvar to the same value,
you can issue "rcon" commands to the remote server :
You can go to different levels, shut the server down, change
cvars, ban people, etc. The output from the command is redirected
over the net and will be echoed on the remote console.
You can also execute commands without even connecting to the
server (if it was full) by setting the "rconadr" cvar to the full
internet address (including port) of the system you want to administer.
2:00 in the morning:
My testarossa snapped another input shaft (the third time).
damn dman damn.
>1000 HP is bad for your drivetrain.
QuakeWorld supports two types of filtering: IP packet filtering
and user id filtering. Userid filtering is the most convenient way
to keep a specific person off of a server, but because anyone can
create as many accounts as they want, a malicious user could just
keep logging back in with a new account. If their ip address is
banned, they won't be able to log on with any account from that
computer. Unfortunately, most dialup accounts give a different ip
address for each connection, so you may be forced to ban an entire
subnet to keep a specific person off.
You can add or remove addresses from the filter list with:
The ip address is specified in dot format, and any unspecified
digits will match any value, so you can specify an entire class
C network with "addip 192.246.40".
Removeip will only remove an address specified exactly the same way.
You cannot addip a subnet, then removeip a single host.
Prints the current list of filters.
Dumps "addip " commands to iplist.cfg so it can be execed at
a later date. The filter lists are not saved and restored by
default, because I beleive it would cause too much confusion.
filterban <0 or 1>
If 1 (the default), then ip addresses matching the current list
will be prohibited from entering the game. This is the default
If 0, then only addresses matching the list will be allowed. This
lets you easily set up a private game, or a game that only allows
players from your local network.
The rendition 3d accelerated version of Quake looks very good.
The image quality is significantly better than software - dithered,
bilinear interpolated textures, and subpixel, subtexel polygon
It is faster than software even at 320*200, and at 512*384 it is
almost twice as fast.
We do take a bit of a hit when we have to generate a lot of 16 bit
surfaces, so occasionally the framerate gets a bit uneven, but
overall it is a very solid improvement.