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Acecube
Feb 1 2003, 11:07
Maybe only someone from BIS can answer this. I realy need info on how the ballistic curve of Bullets is calculated in OFP (bullet trajectory).

Does it contain some sort of air friction factor? I need to know this to make a bullet drop table for a very sophisticated reticle. Please help me cuz the whole project is stalled.

Feb 1 2003, 19:59
I&#39;m not from BIS but I&#39;ve heard that air friction is not computed for bullets in OFP.

Feb 1 2003, 20:12
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (MadDogX @<hidden> Feb. 01 2003,21:59)</td></tr><tr><td id="QUOTE">I&#39;m not from BIS but I&#39;ve heard that air friction is not computed for bullets in OFP.[/QUOTE]<span id='postcolor'>
There is bullet drop in OFP. There is no wind factor, however.

Acecube
Feb 1 2003, 20:35
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (theavonlady @<hidden> Feb. 01 2003,21:12)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (MadDogX @<hidden> Feb. 01 2003,21:59)</td></tr><tr><td id="QUOTE">I&#39;m not from BIS but I&#39;ve heard that air friction is not computed for bullets in OFP.[/QUOTE]<span id='postcolor'>
There is bullet drop in OFP. There is no wind factor, however.[/QUOTE]<span id='postcolor'>
You should perhaps try shooting a M21 or SVD on the Nogova airport from different directions on far targets and you will well see the windrift the bullet gets. (Same thing on the other islands).

Feb 1 2003, 20:43
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Acecube @<hidden> Feb. 01 2003,22:35)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (theavonlady @<hidden> Feb. 01 2003,21:12)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (MadDogX @<hidden> Feb. 01 2003,21:59)</td></tr><tr><td id="QUOTE">I&#39;m not from BIS but I&#39;ve heard that air friction is not computed for bullets in OFP.[/QUOTE]<span id='postcolor'>
There is bullet drop in OFP. There is no wind factor, however.[/QUOTE]<span id='postcolor'>
You should perhaps try shooting a M21 or SVD on the Nogova airport from different directions on far targets and you will well see the windrift the bullet gets. (Same thing on the other islands).[/QUOTE]<span id='postcolor'>
Search The FAQ (http://www.theavonlady.org/theofpfaq/) for "wind". I&#39;m just the messenger. http://www.flashpoint1985.com/ikonboard301/iB_html/non-cgi/emoticons/smile.gif

I have only seen something that looks like windrift on unofficial models, when fire at a target not at the same level as the shooter.

RalphWiggum
Feb 1 2003, 22:02
the possible source of OFP bullets flying to the side is due to elevation of land. in SP mission &#39;underhill&#39;, when you hide under some trees in SW corner of OA, your body is slanted and will cause some drift.

possible reason could be that in prone postion, body&#39;s angle is slanted due to the ground, and thus, will affect bullet trajectory. but the view that we get from scope is still not slanted. this can be corrected by crouching instead of going prone.

Acecube
Feb 2 2003, 16:33
http://www.flashpoint1985.com/ikonboard301/iB_html/non-cgi/emoticons/wow.gif2--></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (RalphWiggum @<hidden> Feb. 01 2003,23http://www.flashpoint1985.com/ikonboard301/iB_html/non-cgi/emoticons/wow.gif2)</td></tr><tr><td id="QUOTE">the possible source of OFP bullets flying to the side is due to elevation of land. in SP mission &#39;underhill&#39;, when you hide under some trees in SW corner of OA, your body is slanted and will cause some drift.

possible reason could be that in prone postion, body&#39;s angle is slanted due to the ground, and thus, will affect bullet trajectory. but the view that we get from scope is still not slanted. this can be corrected by crouching instead of going prone.[/QUOTE]<span id='postcolor'>
BRILLIANT&#33; That explains a lot. I will give it a try. Now only one question is left, how is bullet trajectory calculated in OFP?

Acecube
Feb 7 2003, 08:12
Please, someone from BIS give me the formula used for bullet trajectory (kulka dráha; dráha, trajektorie)&#33;&#33; http://www.flashpoint1985.com/ikonboard301/iB_html/non-cgi/emoticons/biggrin.gif

jacobaby
Feb 13 2003, 18:08
Im purely guessing, but it wouldnt take too much to check out I dont suppose.

The bullets are fired at a set rate in the cfg.

You can alter this for custom weapons.

So if you set the initspeed very low the projectile will only be propelled slightly forward before dropping.

The basic bullets have a "Thrust time" of 1.5 seconds I think, and a thrust of 210 (I think thats in m/sec?)

There is a value "sideairfriction" applied to the bullets, and its value is "1". Its the same for all ammo except the LGB, which has 0.1000. I dont know what this does though.

What figures do you need to be able to work out a trajectory chart?
I would be very interested in seeing this. Perhaps you could message me or something.

TJ

earl
Mar 6 2003, 03:21
I was playing around with ballistics for the VSS Vintorez, and found that with an Init speed of 400, the bullets were actually striking *above* the center of the reticule. I don&#39;t understand this, because the HK MP5 uses init speed of 400 too.

I&#39;d really like to keep the damage pretty high, but use the severely curved trajectory as the balancing factor for the 9x39mm round, since it is a heavy subsonic projectile.

chris330
Mar 6 2003, 21:44
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (jacobaby @<hidden> Feb. 13 2003,19:08)</td></tr><tr><td id="QUOTE">The basic bullets have a "Thrust time" of 1.5 seconds I think, and a thrust of 210 (I think thats in m/sec?)[/QUOTE]<span id='postcolor'>
I think the thrust may even be Newtons per Kilogram, depends on whether or not you have to state a mass (or weight) for the ammunition models. As for the drift part, if you look at the config file for any weapon in ofp you will find a part that states a factor called dispersion. I found that this is what seemed to cause "drift" by realistically distributing the bullets that are fired across a certain small distance either side of the centre aiming point. You should check more thoroughly and you will probably find that on a flat surface the bullets will deviate in both directions from the centre. I dont think this function was intended to simulate drift, rather the slight randomness you would expect when shooting a weapon over any distance.

Tanelorn
Mar 14 2003, 23:25
This may or may not be on topic, but I figured I would share this info...

You must be very careful changing the initspeeds for your weapons. You are very restricted in what velocities you give your ammunition, if the weapon is to be used by the AI.

The AI does a horrible job adjusting to a custom trajectory. Now this may not be true for rifles, as I have seen the AI do a good job aiming high and low velocity bullets and grenades. However, tank shells and unguided shoulder-fired rockets are a different story.

Let me cite two examples:

1. My Core Raider tank fires a shell that has an initspeed of 300m/s. This is far below the usual 700m/s of the other tank shells. When the AI tries to attack with this weapon, it consistantly overcompensates and overshoots the target. Rarely will the AI get a hit on anything beyond 200m

2. My revised Keg RPG7v fires at 250m/s and does not burn fuel en-route. I did this to simulate how the RPG behaves in real life: an initial pop and that&#39;s it. The AI thinks it will fly straight like the BIS RPG, however, so they routinely undershoot targets beyond 200m

In both these examples, lower velocity projectiles cause the AI to miss their targets. A player handles the weapons fine, so long as the optics show proper elevation angles, of course.

You can actually run these tests with BIS vehicles such as the BMP, which has one of the lowest velocity tank shells. WHile the trajectory is fairly flat, any targets beyond 500m are often OVERSHOT due to the bug in AI aiming.

So you all need to keep this in mind. CHange velocities at your own risk.

Fab.
Feb 17 2004, 15:49
I&#39;m having a similar problem. I&#39;m trying to code a sample of ww2 weapons to code my armour/ammo code. In this sample, i&#39;ll have some weapons with very low muzzle velocity, like 180m/s.

At this velocity, i noticed that the gun wont even fire straight. It will behave like a grenade launcher. I expected the bullet to be fired from horizontal and then rapidly curve and drop down after 50-100m, but instead it will fire with an initial angle (i activated the tracers and put them very bright to observe that).

I observe the same problem with all the weapons with initspeed below 400, and having a look at BIS&#39; HK, the initspeed is 400, which is not the HK mp5 muzzle velocity at all.

So i assume initspeed is definitly not the real muzzle velocity of the weapon. Then how i am supposed to determinate the value for that ? Also what is exactly maxleadspeed ?

On the same topic, i have the same problem with tanks where a sherman will be less accurate than a panzer 3 ausf L because of the initspeed thing... Even if my panzer 3 have a stronger dispersion due to its shorter gun http://forums.bistudio.com/oldsmileys/rock.gif

So does anyone knows exactly how this thing works and how can i set a realistic balistic system ?

Fab (wwIIec)

Tannethal
Feb 17 2004, 18:05
When dealing with a mismatch of bullets vs reticle, keep in mind that the reticles are centered at a certain distance.

Code sample from weapons.hpp (comented config.185):

opticsZoomMin=0.35;
opticsZoomMax=0.35;
distanceZoomMin=400;
distanceZoomMax=400;

With this the bullet would be at 400 meters? spot on, plus a bit added dispersion. Above this distance the bullet would drop under the reticle.
Below 400m the bullet would climb above the reticle with a maximum climb roughly at 200 meters target distance&#33; So trajectory and zeroing of the optic are depending upon each other&#33;

This means how fast a target can move at a 90° angle crossing the shooters path and still being aimed at and ultimately hit.
Only at 90° it&#39;s directly the targets velocity above and below 90° it differs from the targets velocity.
Anything crossing right angled in front of the shooter and moving faster than maxleadspeed will not be shoot at. Anything slower will being shoot at with the right dose of lead.

Yet I&#39;m not sure if this is influenced by skill of the shooting AI?

S&#33;

Fab.
Feb 17 2004, 20:03
thanks for the info i&#39;ll try this out.

Baphomet
Mar 7 2004, 04:06
That&#39;s interesting. I always wondered what maxleadspeed did.

It seems to me although I&#39;m just a cpp tinkerer, that if your weapon has a recoil that takes a longer period to rise up coupled with a low muzzle velocity. The bullet actually tends to rise up more. I have found this problem can be circumvented to an extent by making the upward recoil time much shorter.