Bullet velocity - inaccurate ?

[maturin 12]

It seems no one has anything but rule of thumb evidence for the round velocity, but what about range for larger weapons? I found myself unable to reach some trucks with the Shilka's 20mm cannon at 2000 meters, even if I arced it a good ten degrees.

[cartier90 0]

Would be nice to haveone of the inside people comment on wether the drag model is overcooked. Anyone been able to try that script yet , I can't as no net other than phone.

[max power 21]

Well, ballistics mods seem to be able to get excellent agreement with real world behaviour. I don't think NonWonderDog is around anymore, but his work is being picked up by others. Maybe one of the current contributors could answer what the difference is in their mod thread or by PM.

[cartier90 0]

So is there a delay with the dust or or just slow bullets ?

[Deadfast 43]

Here's a test mission. As soon as you fire a gun the time will slow down to 0.1. That should hopefully eliminate any CPU anomalies.

[76 0]

Any of you guys created a ticket at Dev-Heaven?

If you can reproduce or provide some sort of test to demonstrate this is an issue that needs/can be addressed then it will be 'assigined' to a tester, and if the tester can verify that it is a valid issue it will be passed onto a programer and fixed/tweaked... well that's how it's meant to work :)

[Inkompetent 0]

First they need to test by script to actually time the bullet travel time versus the correct time IRL for same distance of travel, then they can start making tickets :)

Stopwatches and a hunch doesn't cut and is a waste of developer time to even look at :P

[maturin 12]

Even stopwatches would be useful if someone could port Arma's bullet cam mod.

[afp 1]

There is one more issue here, since it is a very fast action it may be FPS dependant, it may look normal at 50 FPS and too slow at 25 ...

[dm 9]

Would be nice to haveone of the inside people comment on wether the drag model is overcooked.

The "drag model" is just a config entry, it can be changed easily.

[celery 8]

Excuse me, but what on earth are you guys going on about stopwatches? :crazy:

The game itself can measure time between the shot and the impact.

Here's a mission you can use.

Link

[Spokesperson 0]

First they need to test by script to actually time the bullet travel time versus the correct time IRL for same distance of travel, then they can start making tickets :)

Stopwatches and a hunch doesn't cut and is a waste of developer time to even look at :P

Well, there are models for IRL-bullet flight and if the in-game bullet flight doesn't correspond with them it most likely doesn't correspond with reality either.

I made a very rough comparison between what was reported here and what the model would predict. The conclusion is that the bullets are too slow - if the reported times are correct. It might also be a good idea to disable wind when doing the tests.

So just posting that calculation should be enough - together with a test mission that confirms the reported times.

Here's a simulation (images show drag +-wind, no drag)

Trajectories are almost identical at 400m.

For 469m flight time is about 0.545 s. Far below 1 s. (Very similar to the results of that forumla I posted - which should be more correct).

Edited January 11, 2010 by Spokesperson

[Deadfast 43]

Excuse me, but what on earth are you guys going on about stopwatches? :crazy:

The game itself can measure time between the shot and the impact.

Here's a mission you can use.

Link

Here's a test mission. As soon as you fire a gun the time will slow down to 0.1. That should hopefully eliminate any CPU anomalies.

And here too :p

[cartier90 0]

AFP - testing at 70 fps on urea - very clear even without using above mission that flight times for a 450m shot is close to a second , way over a half. Can anyone please try the above mission at 0.1 speed , I don't have use of my computer at the moment.

[InqWiper 0]

I didnt really get those other 2 posted testmission to work, maybe I didnt try enough. Since my first example was pretty much ignored I made a more advanced mission and uploaded it:

bulletTest.utes

When you fire your weapon a camera will follow the bullet while giving you updates on bullet speed, bullet distance and time passed since shot fired. You can choose slow motion using radio. When the bullet is no longer alive you will get information about initial velocity, final velocity, distance travelled, flight time and average velocity.

To spoil it a bit I can tell you that it takes about 0.8 seconds for an m16 bullet to travel 450 meters.

I hope this helps.

[max power 21]

Well, there are models for IRL-bullet flight and if the in-game bullet flight doesn't correspond with them it most likely doesn't correspond with reality either.

I made a very rough comparison between what was reported here and what the model would predict. The conclusion is that the bullets are too slow - if the reported times are correct. It might also be a good idea to disable wind when doing the tests.

So just posting that calculation should be enough - together with a test mission that confirms the reported times.

Here's a simulation (images show drag +-wind, no drag)

[MG]http://img197.yfrog.com/img197/4323/dragp.jpg[/img]

[MG]http://img35.imageshack.us/img35/3884/dragzoom.jpg[/img]

Trajectories are almost identical at 400m.

For 469m flight time is about 0.545 s. Far below 1 s. (Very similar to the results of that forumla I posted - which should be more correct).

So these graphs are based on hunches? When you're trying to prove a theory, you don't try to gather evidence towards the affirmative. You try to gather proof towards the negative (and hopefully fail).

Edited January 11, 2010 by Max Power

[Spokesperson 0]

No, those are based on existing models for drag, with parameters chosen as listed above.

In order to get flight times of more than one second you would have to have grenade-sized bullets.

And what's affirmative and negative is relative. In order to support a theory you look for evidence, in order to disprove something you look for negatives.

[cartier90 0]

Inq ran a test and .8 was the flight time for 450m - that's too slow.

[max power 21]

lAnd what's affirmative and negative is relative. In order to support a theory you look for evidence, in order to disprove something you look for negatives.

That is exactly wrong. In fact, it's the inverse. The opposite of not incorrect.

In order to test a theory, you must satisfy the null hypothesis test. The null hypothesis is a hypothesis that is any result other than the one you are looking for. You then test to see if you can break your theory using the null hypothesis. If you satisfy the null hypothesis, your theory is bunk. If it impossible to satisfy the null hypothesis, your theory may be correct given your methodology is correct.

[50.cal 10]

Inq ran a test and .8 was the flight time for 450m - that's too slow.

Ok then is there a way to correct that now?

[max power 21]

Config replacement.

Fincuan has ported NonWonderDog's ballistics addon.

http://forums.bistudio.com/showthread.php?t=91188

[50.cal 10]

Thx I'll give it a go!

[Spokesperson 0]

That is exactly wrong. In fact, it's the inverse. The opposite of not incorrect.

In order to test a theory, you must satisfy the null hypothesis test. The null hypothesis is a hypothesis that is any result other than the one you are looking for. You then test to see if you can break your theory using the null hypothesis. If you satisfy the null hypothesis, your theory is bunk. If it impossible to satisfy the null hypothesis, your theory may be correct given your methodology is correct.

No, you don't do that in this kind of context. You have formulas (which you deduce from newtonian mechanics, experiments and dimensional analysis) and you have the parameters, then you do the math and get a result. In this case there's a model of drag that is widely used and accepted for its validity. I have simulated the trajectories for a set of parameters that are natural. My bullets aren't of 20m calibre, and I don't shoot under water. A null hypothesis is completely irrelevant here. Sure, I have tried small deviations to these parameters and as expected there are small deviations to the flight time, it's only when you have grenade sized bullets that you get flight times of over one sec. But I'm not going to test all parameters including the completely unplausible ones.

So if this simulation, using normal parameters, supports the idea that the bullets fly to slow, then it's likely also good evidence that the in-game bullets fly to slow. BIS probably use some simplified numeric integration (not euler backwards) in order to save CPU-time, but then a lot of people have a lot of CPUs.

Edited January 12, 2010 by Spokesperson

[afp 1]

or this one?

http://forums.bistudio.com/showthread.php?t=87648

[InqWiper 0]

or this one?

http://forums.bistudio.com/showthread.php?t=87648

Config replacement.

Fincuan has ported NonWonderDog's ballistics addon.

http://forums.bistudio.com/showthread.php?t=91188

Do these mods also alter drag or just initial velocity? I dont think the issue at the moment is initial velocity, but drag.

I did some testing on several weapons and will post the results below. Slowing down time to 0.1 seemed to result in the bullet hitting its target almost 0.14 seconds later so all tests were performed at normal time. The tests only measure XY velocity not Z. If a bullet is dropping straight down it will return 0 speed.

Press show spoiler to show results:

Bizon shot at 500 meters (9x18):

Initial velocity: 349.219m/s

Final velocity(no not 0 you funny guy you, the one before that): 88.0545m/s

Distance travelled: 499.062m

Flight time: 3.095s

Average velocity: 161.248m/s

Velocity maintained: 25.2147%

Bizon SD shot at 500 meters (9x18 SD):

Initial velocity: 319.515m/s

Final velocity: 124.031m/s

Distance travelled: 499.259m

Flight time: 2.63098s

Average velocity: 189.762m/s

Velocity maintained: 38.8185%

MP5A5 shot at 500 meters (9x19):

Initial velocity: 399.815m/s

Final velocity: 187.829m/s

Distance travelled: 499.191m

Flight time: 1.891s

Average velocity: 263.983m/s

Velocity maintained: 46.9890%

MP5A5SD6 shot at 500 meters (9x19 SD):

Initial velocity: 319.727m/s

Final velocity: 165.713m/s

Distance travelled: 500.115m

Flight time: 2.246s

Average velocity: 222.669m/s

Velocity maintained: 51.8295%

M1911 shot at 500 meters (.45 ACP):

Initial velocity: 259.608m/s

Final velocity: 157.856m/s

Distance travelled: 499.624m

Flight time: 2.51599s

Average velocity: 198.579m/s

Velocity maintained: 60.8055%

AK74 shot at 500 meters (5.45x39):

Initial velocity: 899.994m/s

Final velocity: 446.901m/s

Distance travelled: 498.838m

Flight time: 0.804001s

Average velocity: 620.445m/s

Velocity maintained: 49.6560%

M16 shot at 500 meters (5.56x45):

Initial velocity: 929.997m/s

Final velocity: 453.482m/s

Distance travelled: 498.799m

Flight time: 0.852s

Average velocity: 585.445m/s

Velocity maintained: 48.7617%

M4A1SD shot at 500 meters (5.56x45 SD):

Initial velocity: 319.856m/s

Final velocity: 237.372m/s

Distance travelled: 500.088m

Flight time: 1.84399m

Average velocity: 271.198m/s

Velocity maintained: 74.2121%

AKM shot at 500 meters (7.62x39):

Initial velocity: 709.963m/s

Final velocity: 268.571m/s

Distance travelled: 498.939m

Flight time: 1.21001s

Average velocity: 412.344m/s

Velocity maintained: 37.8433%

Vintorez shot at 500 meters (9x39):

Initial velocity: 299.783m/s

Final velocity: 182.342m/s

Distance travelled: 499.604m

Flight time: 2.183s

Average velocity: 228.862m/s

Velocity maintained: 60.8247%

DMR shot at 500 meters (7.62x51):

Initial velocity: 899.975m/s

Final velocity: 568.629m/s

Distance travelled: 499.447m

Flight time: 0.705017s

Average velocity: 708.418m/s

Velocity maintained: 63.1828%

Dragunov shot at 500 meters (7.62x54R):

Initial velocity: 869.997m/s

Final velocity: 540.838m/s

Distance travelled: 498.858m

Flight time: 0.739998s

Average velocity: 674.135m/s

Velocity maintained: 62.1655%

Saiga shot at 500 meters (12 gauge slug):

Initial velocity: 387.556m/s

Final velocity: 29.0898m/s

Distance travelled: 499.732m

Flight time: 6.074s

Average velocity: 82.274m/s

Velocity maintained: %7.5060

M107 shot at 500 meters (12.7x99):

Initial velocity: 849.986m/s

Final velocity: 663.827m/s

Distance travelled: 499.213m

Flight time: 0.678009s

Average velocity: 736.292m/s

Velocity maintained: 78.0986%

KSVK shot at 500 meters (12.7x108):

Initial velocity: 849.981m/s

Final velocity: 645.956m/s

Distance travelled: 498.806m

Flight time: 0.708008s

Average velocity: 704.52m/s

Velocity maintained: 75.9965%

Interresting to see the quite huge difference between normal bizon and bizonSD. Also obvious sillyness in AKM and Saiga testings.

Edited January 13, 2010 by InqWiper