Bombs are too slow!

[max power 21]

From the biki, the dynamic bullet simulation has two forces, drag and gravity. Those forces both have coefficients. I'm not sure why gravity has a coefficient- it must be for tuning purposes.

I'm not assuming that there is some global gravity value- only surmising it from anecdotal evidence from multiple simulations. What evidence have you that shotshell is correct?

Let's leave criticisms of anecdotal evidence alone. I'm sure everyone knows the relative value and limits of anecdotal evidence, especially me.

Edited December 14, 2010 by Max Power

[[aps]gnat 28]

..... my last post was meant to be a joke ..... but it didnt work on so many "english is not my first language" .... lol, my bad. :P

[noubernou 77]

Just testing a bit with bullet ballistics, and it does appear that they are effected differently than shotShell...

I don't have much scientific proof though cause I got distracted by how pretty ricochets look using the drop command! :D (and then got inspired to make realistic shrapnel for artillery shells... *sigh*).

[vilas 477]

but when you chat about trajectory "bad or good" - it is not issue

trajectory is function of speed, gravity (and of course air Cx stopping force etc. but i don't point them)

so about trajectory (good bullet drop or bad) decide pair of gravity and speed (like in photography, for good picture you need time and aperture and ISO)

so if you will change both - your trajectory should stay the same (just like in photo, no matter if you will take 1/125s, f5.6 with ISO 200 or f5.6 and 1/60 s but ISO 100 or 1/250s and f5.6 but ISO 400 (i don't have camera in hand now) , you will get the same result as picture ,

with lower gravity acceleration, with lower speed - trajectory curve should remain the same

bomb will fall slower (is anyone tested my calculations of free falling) but trajectory curve of shell will be okay (although you will miss APC or soldier - like in my example)

Edited December 15, 2010 by vilas

[noubernou 77]

but when you chat about trajectory "bad or good" - it is not issue

trajectory is function of speed, gravity (and of course air Cx stopping force etc. but i don't point them)

so about trajectory (good bullet drop or bad) decide pair of gravity and speed (like in photography, for good picture you need time and aperture and ISO)

so if you will change both - your trajectory should stay the same (just like in photo, no matter if you will take 1/125s, f5.6 with ISO 200 or f5.6 and 1/60 s but ISO 100 or 1/250s and f5.6 but ISO 400 (i don't have camera in hand now) , you will get the same result as picture ,

with lower gravity acceleration, with lower speed - trajectory curve should remain the same

bomb will fall slower (is anyone tested my calculations of free falling) but trajectory curve of shell will be okay (although you will miss APC or soldier - like in my example)

Except thats not the case in ArmA2, bombs "glide" and don't tend to lose velocity as quickly as other simulations.

You can take a bomb and set its vectorDir so its pitching up, the bomb will begin to climb and not lose velocity at a realistic rate.

It seems like there is a difference between all three of the main simulations, bullet, shell, and bomb, that use gravity. Shell seems to be the only one that really follows the laws of gravity and air resistance close enough to the real world.

[maturin 12]

If bombs don't lose velocity fast enough, then why do they explode so far behind the aircraft? A bomb with a ballistic flight path would explode directly beneath your plane at the low altitudes they are dropped at in-game.

[noubernou 77]

If bombs don't lose velocity fast enough, then why do they explode so far behind the aircraft? A bomb with a ballistic flight path would explode directly beneath your plane at the low altitudes they are dropped at in-game.

That is totally different though. That can be explained with the bomb having a higher drag coefficient than the aircraft, etc. The fact that the bomb will "glide" up and reach a totally un-natural climb speed is the issue.

You can make a bomb/missile climb up a shallow angle till its velocity is 0 then it just drops straight down... :mad:

[max power 21]

but when you chat about trajectory "bad or good" - it is not issue

trajectory is function of speed, gravity (and of course air Cx stopping force etc. but i don't point them)

so about trajectory (good bullet drop or bad) decide pair of gravity and speed (like in photography, for good picture you need time and aperture and ISO)

so if you will change both - your trajectory should stay the same (just like in photo, no matter if you will take 1/125s, f5.6 with ISO 200 or f5.6 and 1/60 s but ISO 100 or 1/250s and f5.6 but ISO 400 (i don't have camera in hand now) , you will get the same result as picture ,

with lower gravity acceleration, with lower speed - trajectory curve should remain the same

bomb will fall slower (is anyone tested my calculations of free falling) but trajectory curve of shell will be okay (although you will miss APC or soldier - like in my example)

Speed in this case is a known quantity, however, because you set the muzzle velocity yourself.

[vilas 477]

you know quantity of measuring units, but you have no idea about lenght of game meter and duration of game second ;)

so you know speed of xyz game meters per second, not xyz m/s

in that case you know that it has velocity xyz something/s

and maybe for that reason we - addonmakers should get some "time table" of movement of bullets/shell

for example shooting to target 1000 meters away and counting /comparing to real life

to manage real measuring unit

if there is a air-block (Cx) coefficient it complicates

but if we "for scientific experiment" put thesis that game is in vacum, and Cx=0

than shooting from bullet v0 500 should give us exact hit of target in 2 s.

but hell, i have no such super-clock to measure this on movie

if anyone has "fraps movie" something like this with "clock" , than count after what time bullet with given speed hits target 1 km away (the slower speed of bullet - the easier to measure)

having result (no mater will it be 2 s, 2.1 s , 2.5 s - we can count game length of 1 km )

if anyone has time and enough measuring skills - take 10 shots, take 10 result and give average time what you get

use AK 7.62 as it is slower speed bullet in game than sniper rifle bullet

i am not home for 2 days, so i can't measure it

but if you will do addon of ammo and magazine with speed=500

shot to 1 km (give weapon big magnification to see target hit)

you'll get time , and than we will know how long travels bullet in distance of 1 km

#define private 0

#define protected 1

#define public 2

#define true 1

#define false 0

#define TEast 0

#define TWest 1

#define TGuerrila 2

#define TCivilian 3

#define TSideUnknown 4

#define TEnemy 5

#define TFriendly 6

#define TLogic 7

class CfgPatches { class VILAS_exp_Forces { units[] = {"vil_exp"}; requiredVersion = 1.0; }; };

class cfgAmmo {class b_762x54 ; class Vil_experiment_Ball : B_762x54 { hit = 20; typicalSpeed = 500; }; };

class CfgMagazines {

class Default;

class CA_Magazine : Default {};

class vil_experimental_mag : CA_Magazine {

scope = public; displayName = exp magazine; ammo = "Vil_experiment_Ball "; count = 20; initSpeed = 500; };

};

class cfgWeapons {

class m24 ;

class vil_exp_gun : m24{

scope = public;

displayName = experimental gun;

opticsZoomInit = 0.1;

opticsZoomMin = 0.001;

opticsZoomMax = 0.1;

distanceZoomMin = 500;

distanceZoomMax = 500;

magazines[] = {"vil_experimental_mag"};

};

};

this should work

having it , you (if vacuum is in game) should kill soldier 1 km away in 2 seconds , zoom is incredible, so you should clearly see unit 1 km away in editor

or maybe very slow velocity and short distance ?

#define private 0

#define protected 1

#define public 2

#define true 1

#define false 0

#define TEast 0

#define TWest 1

#define TGuerrila 2

#define TCivilian 3

#define TSideUnknown 4

#define TEnemy 5

#define TFriendly 6

#define TLogic 7

class CfgPatches { class VILAS_exp_Forces { units[] = {"vil_exp"}; requiredVersion = 1.0; }; };

class cfgAmmo {class b_762x54 ; class Vil_experiment_Ball : B_762x54 { hit = 20; typicalSpeed = 100; }; };

class CfgMagazines {

class Default;

class CA_Magazine : Default {};

class vil_experimental_mag : CA_Magazine {

scope = public; displayName = exp magazine; ammo = "Vil_experiment_Ball "; count = 20; initSpeed = 100; };

};

class cfgWeapons {

class m24 ;

class vil_exp_gun : m24{

scope = public;

displayName = experimental gun;

opticsZoomInit = 0.1;

opticsZoomMin = 0.001;

opticsZoomMax = 0.1;

distanceZoomMin = 100;

distanceZoomMax = 100;

magazines[] = {"vil_experimental_mag"};

};

};

Edited December 15, 2010 by vilas

[noubernou 77]

I think its fairly accurate as basic ballistics calculations work on shotShell sim'd ammo.

Look at the code in the BIS arty module for how it calculates its ballistics tables. Its just a function of gravity and drag over time and it translates almost perfectly in game.

If it were not... I'd be raising holy hell because it'd be impossible to shoot artillery accurately otherwise... :p

I mean, artillery is the pinnacle of ballistics calculations, its all about hitting targets you can't see from very very far away very very accurately, so if the basic functions of ballistics work in ArmA2 for shotShell, I'd consider most of the other measurements accurate... How they are simulated is another question (for shotMissile/shotRocket).

[OChristie 0]

I found a temporary work around, just increase the weight of the munition and increase the speed i'n the configuration file no need to fix gravity as that would change the engine completely.

You need to modify:

maxSpeed

sideAirFriction

airFriction

thrust

It should create the desired effect.

[blakeace 11]

From my experiments with the ballistic behavior of the unguided bombs, I have found using a gravity value of 5.2, and the drag coefficient at about 0.000275 yields reasonably close prediction to their flight path.

Edit: My testing was done prior to the latest 1.56 patch.

Edited December 16, 2010 by blakeace

[maturin 12]

Just dropped some bombs from a hovering Hind (300m altitude) and they flew forward about 150m.

[blakeace 11]

Just dropped some bombs from a hovering Hind (300m altitude) and they flew forward about 150m.

Same with a harrier hovering. Never noticed this in any of my experimenting, though I will admit I never really looked at a stationary delivery platform.

Values from my previous post still seem ok if the vehicle has a reasonable forward velocity. Eg the hind at @130 was tested and the bombs impacted as predicted.

[noubernou 77]

Do the bombs have a thrust value... :?

[max power 21]

Some bombs can glide, like the gbu. That FAB bomb or whatever does lock on to targets and seek, so I'd imagine if it doesn't have thrust, it does have some capability to maneuver (rightly or wrongly, I know nothing of FABs).

[twisted 128]

I found a temporary work around, just increase the weight of the munition and increase the speed i'n the configuration file no need to fix gravity as that would change the engine completely.

You need to modify:

maxSpeed

sideAirFriction

airFriction

thrust

It should create the desired effect.

be nice if a mod folder amending these for all was released with a bikey as well.

[vilas 477]

but has anyone tested falling time and bullet to target on given distance time ?

i gave 2 examples of things to check (but i am not home for 2 days ) so i can't test it

---------- Post added at 09:12 AM ---------- Previous post was at 09:12 AM ----------

be nice if a mod folder amending these for all was released with a bikey as well.

first we moders have to know coefficient real-life/game

than we as moders can rework our speed and mass values in addons :]

[noubernou 77]

Some bombs can glide, like the gbu. That FAB bomb or whatever does lock on to targets and seek, so I'd imagine if it doesn't have thrust, it does have some capability to maneuver (rightly or wrongly, I know nothing of FABs).

FAB are usually just normal GP iron bombs with no guidance/propulsion (think of them as the US MK series).

[[frl]myke 14]

FAB are usually just normal GP iron bombs with no guidance/propulsion (think of them as the US MK series).

Correct, the russian GBU (laserguided) counterpart would be the KAB series.

[Opticalsnare 12]

The problem is that bombs dropped by aircraft atm are dropped from a very low height and so they simply glide to their targets without picking up much speed. Drop them from 5000-10000ft and it looks completly differnt they serously slam into their targets. We need to make the aircraft themselfs drop the bombs at a much higher attitude.

[noubernou 77]

Yea, thats my plan for better laser guidance as well as JDAM. The problem now is that pilots have to see the target or the laser marker to drop a bomb on it.

JDAM and LGB that isnt the case. You can fly very high in ArmA2 and drop bombs. Course thats not as sexy flying in low and straffing the target with a full Harrier of LGB... but it is a little more realistic. :p

[vilas 477]

if any of you would measure time of some falling/bullet fly - we could discuss on facts , math, not feelings

[noubernou 77]

if any of you would measure time of some falling/bullet fly - we could discuss on facts , math, not feelings

Vilas I doubt any of us here have the equipment to take an accurate measurement of a real bullet.

I did the math with the ballistics calculator that comes with ArmA2 that Headspace wrote for the Arty Module. I made a b-table for a 7.62 round and the rounds consistently fell short by about 100m to what the b-table calculated they would fall at. The TOF was also off.

[[frl]myke 14]

If this helps, i've measured (roughly) the droptime from a hovering Mi-24, dropping FAB-25:

Height: 100.394m

Time: 8.209s

Height: 201.315m

Time: 11.377s

Height: 301.501m

Time: 13.426s

Height: 401.541m

Time: 14.963s

Height: 401.587m

Time: 15.122s

The script used:

private ["_veh"];
_veh = _this select 0;
glt_measure = {
private ["_veh", "_bomb", "_height", "_released", "_falltime"];
_veh = _this select 0;
_bomb = _this select 6;
_height = getposATL _veh select 2;
_released = time;
waituntil {!alive _bomb};
_falltime = time - _released;
hintsilent format ["Height: %1\nTime: %2", _height, _falltime];
};
_myEH = _veh addeventhandler ["fired", {nul = _this spawn glt_measure}];
hintsilent "Ready";

Probably not high science but i guess it did the job pretty well.