Como Entender el LAGOMETER?

[neim]

PRIMER HIT EN GOOGLE

April 26, 1999 (From John Carmack's .plan)
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Interpreting the lagometer (the graph in the lower right corner):

The upper graph (blue/yellow) slides one pixel for every rendered frame. Blue lines below the baseline mean that the frame is interpolating between two valid snapshots. Yellow lines above the baseline mean the frame is extrapolating beyond the latest valid time. The length of the line is proportional to the time.

The lower graph (green/yellow/red) slides one pixel for every received snapshot. By default, snapshots come 20 times a second, so if you are running >20 fps, the top graph will move faster, and vice versa. A red bar means the snapshot was dropped by the network. Green and yellow bars are properly received snapshots, with the height of the bar proportional to the ping. A yellow bar indicates that the previous snapshot was intentionally
supressed to stay under the rate limit.

The upper graph indicates the consistancy of your connection. Ideally, you should always have blue bars of only a pixel or two in height. If you are commonly getting big triangles of yellow on the graph, your connection is inconsistant.

In a heavy firefight, it is normal for modem players to see yellow bars in the bottom graph, which should return to green when the action quiets down. If you are getting several red bars visible, you may want to look for a server that drops less packets.




Number 1 is a normal, stable lagometer display, with a narrow, flat green line at the bottom, which reflects a fairly low (50) and stable ping. The upper blue line has only a tiny bit of yellow in it. Yellow above the blue line is undesirable, since these are frames that are extrapolated by your client, which means that it is making a kind of educated guess about where moving objects are, in the absence of "real" snapshot data from the server.

Number 2 contains many yellow triangles above the blue, but there is still blue in between them. The blue indicates frames that are interpolated between valid snapshots, but the yellow means that the client is extrapolating outside of valid snapshot data. The height of the yellow indicates the time since the last valid snapshot, which is why triangles form. The longer the time without a valid snapshot, the higher the yellow line, until valid snapshot data is again rendered and the yellow suddenly disappears. When this happens, the client will put players back where the server says they should be, which may not be where the client had extrapolated their movements. The game would appear choppy as the cycle of extrapolate/correct/extrapolate/correct continued.

Number 3 shows a large yellow triangle forming at the edge of the lagometer. As time passes without a valid snapshot having been rendered, the height of the triangle grows accordingly. This is a graphic representation of the phenomenon of lag. Note that there are spikes in the green, showing that the client's ping is momentarily climbing.

Number 4 shows red spikes, which mean that snapshots have been dropped by the network, either in transmission (packet loss) or because the client can't handle them (cpu tied up by other tasks, like taking repeated screenshots.) CoD and all Quake-engine games use UDP packets because they are fast and easy to handle, but they have no retransmission or error-correction capability. The server sends them and forgets about them. Once lost, they are lost for good. Red spikes like these occur from time to time, and occasional red spikes are not necessarily bad unless they are wide (each pixel in width is one snapshot lost) or frequent. During DoS attacks on our host, the lagometer will show almost solid red. (Red spikes will always be this height. There is no meaning associated with the height, which is purely arbitrary.)

Number 5 shows a big yellow triangle, which would manifest in-game as a brief freeze, followed by players "teleporting" to nearby locations as the client gets correct information from the server. Remember, any yellow means the client is trying to guess where players should be in the absence of proper information from the server.

Number 6 shows a long string of connected yellow. With no blue in sight, any movement by the player will result in the "skating" or "rubber-band" effect, where the player is "snapped back" to where the server last put him. This shot is not really typical of that effect, since it was the result of taking many back-to-back screenshots. When this happens spontaneously in the game, a triangle will form that grows to the top of the lagometer, so what you really see is a yellow bar all the way to the top.

Remember, the only thing that is "really" happening in-game is what the server is calculating. If the server cannot get this information to the client, the client will render a guess about what is going on. Since players move at about 10 feet per second in the game, one missed snapshot can make a difference of 6 inches in location.

Four missed snapshots (one-fifth of a second in duration) can make a difference of two feet! This is why your client sometimes appears to show a sure hit, but the server may register a clean miss. Playing with the lagometer on can help you understand what is "really" going on in the game.


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