Author Topic: Lag and collision  (Read 612 times)

Offline Yenny

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Lag and collision
« on: August 20, 2008, 09:41:17 PM »
We had a discussion about lag/collision. I'd like to point it out that depend on the lag, the server see it differently. Such as an overshootin plane hitting its target can default to the target as leadin the collision. Another example is a plane diving on an afk plane and collided, it could penalty the AFK plane rather then the one diving.

How lag work explained by Hammer:

Understanding Lag and its Effects on Aces High
by Hammer

When you are flying on-line in Aces High, your plane exists in multiple virtual realities. The one you are aware of is the one you can see on your screen. You know where your plane is and where other planes within visual range are. What you might not realize is no two players' reality is exactly the same. Each player playing the game sees every plane, including yours, in a slightly different place from every other player. These differences occur because of the way lag affects the game. Lag is the time it takes for information from one player’s computer to reach another player’s computer.
Lag

For you to see what another player is doing, information must pass from the Aces High software (called the front-end) on his computer to the server (called the host), be processed by the host, and then pass from the host to the front-end on your computer. At the same time, information from your front-end is being passed to the host, processed by the host, and then passed from the host to other players. The time it takes for information to move from your computer to the host is the ping time indicated on your clipboard when you bring up the on-line arenas.



The time it takes for information to pass between players is the sum of the ping times of the 2 players and the Host queue time. This total time is commonly referred to as lag.

In the illustrations below, the bright Green and Red icons represent what Player 1 sees on his computer while the faded Green and Red icons represent what Player 2 sees on his computer.

Let’s say each player has an identical ping time of 50 milliseconds. That means information from Player 1’s front-end reaches Player 2’s front-end in about 100 milliseconds, or 1/10 of a second. If Player 2 is sitting in the tower watching Player 1 fly past at 360 mph, Player 2 will see Player 1’s plane at point B while Player 1 sees himself at point A. The distance (x) between A and B in this example would be 52.8 feet – more than the length or wingspan of most fighters! (360mph = 528 feet/sec; x = 528f/s x .1s = 52.8 ft) Note that the result would be the same if one player had a ping time of 60ms and the other 40ms. It is only the total time that matters, not one or the other.

Now let’s say Player 1 and Player 2 are opponents and flying in opposite directions at 360mph. Again, both have an identical ping time of 50 milliseconds. In this case, the distance between the two realities remains the same 52.8 feet but, because of lag, Player 1 sees the two planes passing each other at point A while Player 2 sees both planes passing at point B. Because both plane's speeds are identical, they pass at the same time, but not the same place.

The results are a bit different if speeds are not the same. If Player 1 is moving at 360mph but Player 2 is moving at only 180mph, x remains 52.8 ft but y is only 26.4 ft. When Player 1 is even with Player 2 on his (Player 1's) front-end, Player 2 is still in front of Player 1 on Player 2's front-end. Now not only will the place where Player 1 and Player 2 pass each other be different, but so will the time. While we are only talking 1/100s of seconds and a few extra feet of maneuver room, it is still a difference that can and does lead to confusion, misunderstanding, disbelief, and sometimes hostility in the

Collisions

Collisions and how they are modeled is one of the most misunderstood, and therefore most contentious, issues in the game. The usual question is how 1 player can suffer catastrophic damage in a collision while the other player suffers no damage at all. The explanation is in the understanding of how lag affects the reality on the two front-ends and how HiTech mitigates collisions.
The first thing you must understand is that a collision can occur on one front-end but not on the other. The reason for this is the different realities caused by lag. Player 1 can see himself safely past Player 2 at point A while at exactly the same time Player 2 sees himself colliding with Player 1 at point B. Whether through maneuvering to avoid the collision or just plain luck, Player 1 did not collide on his front-end. Player 2 did.

Since a picture is worth a thousand words, take a look at the images below. They are from films of a duel between Bronk and Tangle. The first picture is from Bronk's film and clearly shows Bronk colliding with Tangle.



The second picture is from Tangle's film and shows Tangle's view at exactly the same instant. Notice the "Bronk has collided with you" message in the text buffer. In Tangle's view, though, there is almost two plane lengths of separation between him and Bronk.



The second key to understanding collisions is knowing how HiTech mitigates collisions. It's really very simple: If a collision occurs on your front-end, you suffer damage from the collision. If a collision does not occur on your front-end, you do not suffer damage. Looking at the two images above, it is pretty clear that this is the only way to do it. How would you like to be Tangle in this scenario and receive damage from a collision you were obviously not involved in?
There are lots of scenarios where a collision can occur on 1 front-end and not the other. You may not even see the collision (i.e. you were looking a different direction) and suddenly suffer collision damage. You may see the collision, but the other guy maneuvered out of the way. The bottom line, though, is in your front-end's version of reality, a collision occurred. If a collision did not occur on the other front-end's version of reality, the other player's plane will not suffer damage.

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Offline Yenny

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Re: Lag and collision
« Reply #1 on: August 20, 2008, 09:42:20 PM »
Warps

Warping is usually caused by extreme variations of lag. Your front-end is constantly updating the position of the other planes you can see based on the data sent to you from the host (comments). Before it can be sent to you, though, the host must get it from the other planes' front-ends. If no update is received, the other plane continues on the path it was following until an update is received. Once that update finally arrives, the other plane is moved to its new position almost instantly. In other words, it warps there. Usually, this is caused by variations in lag - either yours or theirs. If lag is consistently bad enough for warping to occur between each update, the offending player is going to get a beacon or be disconnected completely.

If you see everybody warp, it is probably your connection causing the problem. You can quickly check to see if your connection has taken a hit by bringing up your clipboard, right clicking on the map, and clicking "Net Status" on the pop-up menu. This will show two graphs. The "Variance in Delay" graph should be flat and close to center. If there is a spike in it, you have taken a hit on your internet connection. While you can live with an occasional hiccup in your connection, you will want to isolate and fix anything that causes constant spiking on this graph.
"Impossible" Shots

Another phenomenon caused by lag is taking hits from "impossible" angles or even after the attacker has already passed you. While more of an annoyance than a contentious issue, understanding how it happens can help you defend against it.
As already discussed, lag causes a different reality on different front-ends. This difference in reality can allow an attacker to shoot when the defender thinks he is safely outside the attacker's line of fire. Unlike collisions, if you opponent scores hits on your plane on his front end, the damage caused by those hits is assessed against your plane. Again we are only talking 1/10’s of seconds and a few extra feet of maneuver space, but it still may be the difference between having a shot opportunity and not having one. This is also how you can get shot after you have passed. Once the host receives hit data from Player 2's front-end, it sends the pings and damage to your front-end - all after you saw your opponent pass you!

This has been described as being like you are towing a target behind you. You can't see it but the enemy can and, if the enemy shoots the target, you take the hits! You can defend against this, though, by paying attention and getting a feel for the angles that people can get hits on you. Once you know this, you adjust your thinking accordingly.
So What?

So how does this apply to how you fly? There are a few things you need to take with you:
# Offense - Aim based on what you see on your screen. If your bullets hit your target on your front-end, that damage is assessed against your opponent.


# Defense - Keep in mind that, on your opponent's front-end, he is a bit ahead of where you see him and and you are a bit behind where you see yourself. If your opponent can hit what he sees, you will take damage.
Think about preventing him from being able to shoot that target sleeve you are towing behind you!

# Collisions - While you may not be able to prevent someone from flying through you and causing a collision on your front-end, remember that he may not have seen a collision on his front-end and, as far as he is concerned, a collision did not occur. While it may be frustrating to watch the other guy fly away while you tumble to the ground with damage from a collision, it beats the alternative of you tumbling to the ground when you know for a fact that you were not part of a collision.

Hope this helps your understanding of how lag affects Aces High!

ALL CREDIT TO HAMMER, I JUST CUT AND PASTE BECAUSE SOME PEOPLE CAN'T FIND IT.
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Offline Masherbrum

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Re: Lag and collision
« Reply #2 on: August 20, 2008, 09:45:45 PM »
Again Yenny so you can understand it easier without the text buffer scrolling fast.

You griped to xbrit about him "ramming you", yes you griped.    The problem isn't lag.   The problem is you rolled a Ta152 and tried turn fighting not only one, but TWO Spit 1's OTD.   You brought the wrong tool out of the toolbox.    You brought it out again for the next hop and we know happened when you were in front of my Ki-61.  

Does lag happen?   Sure it does.   Does collisions happen?   Absolutely.    I'm merely showing you the bigger picture looking through the "lag" issue.  
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Offline mensa180

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Re: Lag and collision
« Reply #3 on: August 20, 2008, 09:49:40 PM »
Where does Yenny ever make reference to what you are talking about?  Seems to me like he's just posting good info to help inform all the guys who have started collision threads easily.
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Offline Yenny

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Re: Lag and collision
« Reply #4 on: August 20, 2008, 09:50:57 PM »
I'm "not whining" or anything. I'm trying to explain how in certain situation you "can't" trust the "Name has collided with you."
My 152 did rollin scissor vs 2 spit1, but the thing is the spit1s overshot and collided. I was infront of the spits, not behind. When the spit over shot usually it's running into. I'm just really trying to explain how the lag effect AH2. No whine what so ever. I took a 152 to furball otd vs tons of baddies, I know imma die. I'm not gunna argue on that.
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Offline Masherbrum

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Re: Lag and collision
« Reply #5 on: August 20, 2008, 09:51:47 PM »
Where does Yenny ever make reference to what you are talking about?  Seems to me like he's just posting good info to help inform all the guys who have started collision threads easily.

You weren't talking to him on 200 tonight.   What I mentioned is EXACTLY what this post is about.    Info aside, there is an "underlying" message to xbrit.   Yenny was repeatedly telling xbrit (how long has Xbrit been playing?) "To read the forums about lag."  

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Offline Masherbrum

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Re: Lag and collision
« Reply #6 on: August 20, 2008, 09:53:57 PM »
I'm "not whining" or anything. I'm trying to explain how in certain situation you "can't" trust the "Name has collided with you."
My 152 did rollin scissor vs 2 spit1, but the thing is the spit1s overshot and collided. I was infront of the spits, not behind. When the spit over shot usually it's running into. I'm just really trying to explain how the lag effect AH2. No whine what so ever. I took a 152 to furball otd vs tons of baddies, I know imma die. I'm not gunna argue on that.

I never said you whined.   You mentioned the word.   I said you griped because you WERE pissed.   I'm out, just wanted to give the rest a good factual synopsis of the thread.   I'm not getting into splitting hairs arguments over something trivial as this.   No pissing contest needed either.   
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Offline Yenny

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Re: Lag and collision
« Reply #7 on: August 20, 2008, 09:54:10 PM »
You weren't talking to him on 200 tonight.   What I mentioned is EXACTLY what this post is about.    Info aside, there is an "underlying" message to xbrit.   Yenny was repeatedly telling xbrit (how long has Xbrit been playing?) "To read the forums about lag."   



Yes, I tried to point to xbrit that you "can't trust the collision model" because lag effect it too. Which was why i used the example "We had a discussion about lag/collision. I'd like to point it out that depend on the lag, the server see it differently. Such as an overshootin plane hitting its target can default to the target as leadin the collision. Another example is a plane diving on an afk plane and collided, it could penalty the AFK plane rather then the one diving." as trying to paint a picture of what I mean.
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Offline Murdr

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Re: Lag and collision
« Reply #8 on: August 20, 2008, 10:00:33 PM »
We had a discussion about lag/collision. I'd like to point it out that depend on the lag, the server see it differently. Such as an overshootin plane hitting its target can default to the target as leadin the collision. Another example is a plane diving on an afk plane and collided, it could penalty the AFK plane rather then the one diving.

Can someone translate this for me?  The only thing I can really make out is something about the "server see[ing] it differently".  Which is not quite right if we are talking about collisions.  The two players front end sees things differently due to the time it take to relay data.  If a collision happens the players front end implements the appropriate damage, and informs the server.  The server just relays the message "so-n-so collided with you" to the 2nd player and tells his front end to display the 1st players damage accordingly.
« Last Edit: August 20, 2008, 10:03:30 PM by Murdr »

Offline crockett

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Re: Lag and collision
« Reply #9 on: August 20, 2008, 10:07:19 PM »
Regardless of lag and warp, it's still annoying as hell having someone ram you and you take damage while they fly off unharmed. Today at fighter island I was in a low E roll over when a 190 I was fighting goes vertical with no possible chance at a shot on me. His wing cuts right through my fuselage and left wing, ripping my aircraft to pieces and he took no damage at all. No way was he going to make a shot on me, but the ram takes me out with a mistake on his part yet I pay for it.

Same thing happened the other night at TT island but instead it was my fault. I came up under a con but totally misjudged my merge and I caused a ram where I came up right in front of him. Was totally my fault for the ram yet I walked away with no damage and he fell away in pieces.

So it still sucks to have it happen especially when it wasn't your fault.
« Last Edit: August 20, 2008, 10:13:30 PM by crockett »
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Offline The Fugitive

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Re: Lag and collision
« Reply #10 on: August 21, 2008, 06:58:10 AM »
its very simple people.....if you DON'T RUN INTO THEM YOU DON'T TAKE DAMAGE! If you are in a rolling scissors and you start getting close, either change your angle, or risk ramming/being rammed on your front end.

Offline dedalos

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Re: Lag and collision
« Reply #11 on: August 21, 2008, 07:42:39 AM »
Where does Yenny ever make reference to what you are talking about?  Seems to me like he's just posting good info to help inform all the guys who have started collision threads easily.

lol, yep.  Just update the pics to add ping + 250ms
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Offline SlapShot

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Re: Lag and collision
« Reply #12 on: August 21, 2008, 07:55:39 AM »
I'm "not whining" or anything. I'm trying to explain how in certain situation you "can't" trust the "Name has collided with you."

If you believe that, then you really don't understand how "collisions" are implemented.
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Offline Chalenge

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Re: Lag and collision
« Reply #13 on: August 21, 2008, 08:25:49 AM »
Yenny I have collided with a lot of planes. Enough planes anyway to tell you I learned how it works really really well. If I dont actually fly into another plane or allow one to fly through me then I dont ever have a collision. Its just that simple. The first time you do fly through another plane or allow one to hit you (even if you want to get out of the way but cant) then you collide.

It doesnt matter to you what the other guy sees on his computer. If you get shot then thats another topic. Many many many people think when they see the collision message that the shot that hit them and caused damage was actually caused by a collision. It was NOT.
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Offline haasehole

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Re: Lag and collision
« Reply #14 on: August 21, 2008, 09:07:36 AM »
   had a bad lag experance last nite me and a squadie had a vh camped ( troops otw) tanks would up fire at me before they would show up. i'd fire when they shoot at me but no hit's thoo until the fully materlized. next time i'm parking some where else  :O
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