Bomb physics.

[CyclonicTuna 87]

I was hoping that with the implementation of PhysX, which is far from perfect I'll admit, BI would take the time to implement proper bombing physics. One thing that has always really bothered me is the fact that bomb don't gain any speed and sort of, float down to the ground like a leaf, or a stone that sinks.

A decently sized bomb will break the sound barrier when dropped from lets say 30.000 feet. A 200 pound Jdam, when goes into a steep dive when it nearly reaches the target and can achieve the speed of sound when dropped from 10000 feet. But In Arma they don't, they fly really slow and it just annoys me beyond belief.

I wonder if it is possible to introduce an accurate physics engine for bombs. I know similair systems have been implemented for other games: http://www.moddb.com/mods/wicmw/features/flint-lead-pursuit-guidance-principles.

Because in real life you rarely even see the bomb before it hits:

[zapat 56]

I made tests in A2: the physics seemed to be okay on the bomb. (I manually calculated the position of a bomb according to basic gravity & speed calculations: the bombs arrived where they should have).

Edit: WRONG! Normal objects are okay, bombs do glide a lot!

see: http://forums.bistudio.com/showthread.php?171179-Bomb-physics&p=2594876&viewfull=1#post2594876

Edited January 8, 2014 by zapat

[progamer 14]

I agree, gravity affecting speed is something that needs to be added to the ballistics model.

Edited January 7, 2014 by ProGamer

[Nexerius 10]

I agree.

I've also been very unsatisfied by the looks and sounds of explosions.

Most of the time they sound really bad...

[CyclonicTuna 87]

I agree.

I've also been very unsatisfied by the looks and sounds of explosions.

Most of the time they sound really bad...

Allow met to introduce:

http://forums.bistudio.com/showthread.php?162988-Blastcore-A3

http://forums.bistudio.com/showthread.php?170226-Jsrs-2-0

[spookygnu 563]

Yeah I just admit, last night was my first time flying an f18 in a group. We scrambled the jets whilst the base was under attack. (pretty cool taking off on the runway, with grenades exploding next to me, lol!) anyway, we made a number of attack runs on the enemy and one of them was a laser guided bomb. When that got fired I had was below 600 meters, and I followed it for another two. Then broke the attack and went round again.

When I followed the bomb, I had chance to think, thats a nice view, if I thought thought quick enough I would've taken a screen shot I had that much time between firing and breaking off. The bomb was waaaay to slow on the decent.

[maturin 12]

Uh... are you guys actually pickling from 30,000 feet? Or just expecting the bombs to magically accelerate from 3000 to resemble youtube footage?

[CyclonicTuna 87]

Uh... are you guys actually pickling from 30,000 feet? Or just expecting the bombs to magically accelerate from 3000 to resemble youtube footage?

30.000 feet is about the maximum hight of many combat aircraft, and also the maximum effective range for laser guided bombs. GPS guidance however doesn't really have a maximum range. So if a 2000lbs JDAM drops from 30.000 feet, it will reach the ground sometimes pushing mach 2. Which is not what you saw in the Youtube video's because a projectile falling at that speed is almost invisible to the naked eye. But if we take for instance a bombing run by an A10 from 9.000 feet, which is a very reasonable hight to fly in Arma 2, the bomb will still hit the ground going 5 or 6 hunder miles an hour, what you saw in the video.

In Arma however, the bomb doesn't accalerate at all. It falls from the aircraft and maintaines a very slow glide untill it hits the ground.

To awnser you're question. Yes, if you fly to 30.000 feet in Arma, which is about 10 km, and drop a bomb, it will not accelerate. But even if you were to drop from a lower altitude, as stated above (9.000 feet), the bomb would still impact a lot faster than it is going in vanilla Arma.

[roshnak 41]

30.000 feet is about the maximum hight of many combat aircraft

What.

[maturin 12]

In Arma however, the bomb doesn't accalerate at all. It falls from the aircraft and maintaines a very slow glide untill it hits the ground.

Not sure I believe that without proof. It's a pain in the ass to test, but I just dropped a bomb from 4000m while diving at 450 km/h. They both zoomed out of sight as I dived at a constant rate, and blew up in a few seconds.

[CyclonicTuna 87]

Not sure I believe that without proof. It's a pain in the ass to test, but I just dropped a bomb from 4000m while diving at 450 km/h. They both zoomed out of sight as I dived at a constant rate, and blew up in a few seconds.

I believe a bomb is given a fixed velocity when deployed from a aircraft, which also means that when it goes into a steep dive when, for instance, released at the very last second, all that forward momentum is converted in downward momentum, which isn't exactly how it works in real life. For instance in real combat situations pilots often deploy a tactic where they lob a bomb to make it fly further then when doing a conventional release. These things arn't possible in Arma.

---------- Post added at 12:34 AM ---------- Previous post was at 12:28 AM ----------

What.

Well operational cieling is the correct term. Aircraft like the F-15 and the Mig 35 will reach 55.000 feet when possible, but there's a lot of factors, mainly wieght that add, or rather subtract from the maximum operational ceiling. If they maintain for instance an altitude of above 50.000 feet the're engine ISP decreases to the point where long missions become unmaintainable.

[maturin 12]

Bombs accelerate. I just saw it with my own eyes. My velocity was steady or increasing in the dive, yet the bombs zoomed out of sight.

[CyclonicTuna 87]

Bombs accelerate. I just saw it with my own eyes. My velocity was steady or increasing in the dive, yet the bombs zoomed out of sight.

Like I said, after release it given a fixed velocity. That velocity is greater than yours but they don't accelerate. And If they do, they don't do at 9.81m/s squared. Try it with a very fast plane like the SU-35: http://www.armaholic.com/page.php?id=24024

Go into a steep dive, full afterburner and release the bombs. You overtake them in the dive because they keep to their fixed velocity.

Edited January 8, 2014 by CyclonicTuna

[maturin 12]

I still need actual proof.

Obviously a diving jet overtakes the bombs, because the jet is already going faster than the bombs' terminal velocity, so they slow due to drag.

[zapat 56]

Run this script, and watch up!

//function for calulating gravity
_goodGrav = 
{
   private ["_b","_velb","_vx","_vy","_vz"];

   _b = _this select 0;
   _velb = velocity _b;

   _vx = _velb select 0;
   _vy = _velb select 1;
   _vz = _velb select 2;

   _vz = 0;

   PrevTime = diag_tickTime;
   waitUntil
   {
       _vz = _vz - 9.81 * (diag_tickTime - PrevTime);
       _b setVelocity [_vx,_vy,_vz];

       PrevTime = diag_tickTime;
       isNull _b || ((getPosATL _b) select 2) < 2
   };

   player sidechat "done";
};



GoodGrav_o1 = "Land_WaterBarrel_F" createVehicle [0,0,0];
GoodGrav_o1 setPos [(getPos player select 0) + 20, getPos player select 1, 500];//500 height
GoodGrav_o1 setVelocity [0,50,0];    //initial velocity

GoodGrav_o2 ="Land_WaterBarrel_F" createVehicle [0,0,0];
GoodGrav_o2 setPos [(getPos player select 0) + 20, (getPos player select 1) + 10, 500];    //500 height
GoodGrav_o2 setVelocity [0,50,0];        //initial velocity
[GoodGrav_o2] spawn _goodGrav;        //script attached 



GoodGravIcons = 
{
   drawIcon3D ["", [1,0,0,1], getPos GoodGrav_o1, 0.5, 0.5, 0, "", 0, 0.03 * safezoneH, "PuristaMedium"];
   drawIcon3D ["", [0,0,1,1], getPos GoodGrav_o2, 0.5, 0.5, 0, "", 0, 0.03 * safezoneH, "PuristaMedium"];
};
PLGRM_TACV_oefId = ["PLGRM_TACV_oefId", "onEachFrame", "GoodGravIcons"] call BIS_fnc_addStackedEventHandler;

One icon is tied to a waterbarrell being handled by the engine,

The other is tied to one being handled by the script, and adjusting 9,81m/s2 on each frame.

Both have some initial velocity. Play with the numbers.

They seem to fall together. I hope I got the physics part all right. :)

[CyclonicTuna 87]

I still need actual proof.

Obviously a diving jet overtakes the bombs, because the jet is already going faster than the bombs' terminal velocity, so they slow due to drag.

Except for the fact that a bomb has a much greater weight to drag ratio than an airplane, because its a bomb. That's what bombs are designed for. They're long and sleek for a reason. In Arma a plane can't even reach the real terminal velocity of a real GBU, so the bomb should always accelerate away from the aiplane even when released at high speed. Unless the plane is diving it at over 2000 km/h the bomb should fall away from the plane.

---------- Post added at 04:15 PM ---------- Previous post was at 04:14 PM ----------

Run this script, and watch up!

//function for calulating gravity
_goodGrav = 
{
   private ["_b","_velb","_vx","_vy","_vz"];

   _b = _this select 0;
   _velb = velocity _b;

   _vx = _velb select 0;
   _vy = _velb select 1;
   _vz = _velb select 2;

   _vz = 0;

   PrevTime = diag_tickTime;
   waitUntil
   {
       _vz = _vz - 9.81 * (diag_tickTime - PrevTime);
       _b setVelocity [_vx,_vy,_vz];

       PrevTime = diag_tickTime;
       isNull _b || ((getPosATL _b) select 2) < 2
   };

   player sidechat "done";
};



GoodGrav_o1 = "Land_WaterBarrel_F" createVehicle [0,0,0];
GoodGrav_o1 setPos [(getPos player select 0) + 20, getPos player select 1, 500];//500 height
GoodGrav_o1 setVelocity [0,50,0];    //initial velocity

GoodGrav_o2 ="Land_WaterBarrel_F" createVehicle [0,0,0];
GoodGrav_o2 setPos [(getPos player select 0) + 20, (getPos player select 1) + 10, 500];    //500 height
GoodGrav_o2 setVelocity [0,50,0];        //initial velocity
[GoodGrav_o2] spawn _goodGrav;        //script attached 



GoodGravIcons = 
{
   drawIcon3D ["", [1,0,0,1], getPos GoodGrav_o1, 0.5, 0.5, 0, "", 0, 0.03 * safezoneH, "PuristaMedium"];
   drawIcon3D ["", [0,0,1,1], getPos GoodGrav_o2, 0.5, 0.5, 0, "", 0, 0.03 * safezoneH, "PuristaMedium"];
};
PLGRM_TACV_oefId = ["PLGRM_TACV_oefId", "onEachFrame", "GoodGravIcons"] call BIS_fnc_addStackedEventHandler;

One icon is tied to a waterbarrell being handled by the engine,

The other is tied to one being handled by the script, and adjusting 9,81m/s2 on each frame.

Both have some initial velocity. Play with the numbers.

They seem to fall together. I hope I got the physics part all right. :)

Could you make a video of it? I can't seem to make it work, I'm not a miracleworker in the Arma 3 editor :P.

[zapat 56]

Yup:

[CyclonicTuna 87]

Yup:

Well if that settles the gravity question than the only thing I could think of are the lifting bodies. Because a bomb shouldn't be able to glide at such a low angle with such low speed as they do in Arma 3 right now. Because a bomb is essentially like a big bullet which has slightly better lift, but only slightly. In order to get the forward distance that they travel right now they would need a hell of a lot more speed. Like 10 times the speed. In other words, the lifting bodies of the bomb are way off. It glides like an airplane but it should fall like a.... well like a bomb.

It should start doing a nosedive after release, in an arch which size is variable to the speed of release. With the only exception to that rule being that if the bomb has a lot of speed, its fins could carry it a bit further if instructed to do so by the GPS or LHS. Either way, if its not the gravity that should be fixed, its the lifting bodies.

[zapat 56]

What is the class of a bomb? I can do the test with that too.

[CyclonicTuna 87]

What is the class of a bomb? I can do the test with that too.

I believe these are the classnames for bombs:

2Rnd_GBU12_LGB

2Rnd_GBU12_LGB_MI10

2Rnd_Mk82

2Rnd_Mk82_MI08

[zapat 56]

Those are magazines. Not createVehicleable.

[CyclonicTuna 87]

Isn't the name the same except for the the "2Rnd_"?

---------- Post added at 05:23 PM ---------- Previous post was at 05:20 PM ----------

Does this help?: http://www.armaholic.com/forums.php?m=posts&q=7963

[Champy_UK 1]

Been watching this thread as im testing for a Domination artillery system...

All these work created on the ground at a marker using create vehicle....

Bo_GBU12_LGB_MI10- big explosion

Bo_Air_LGB -tiny explosion

Bo_Air_LGB_hidden -tiny explosion

Bo_GBU12_LGB - nice big explosion

Bo_Mk82_MI08 - nice big explosion

M_Mo_120mm_AT - works

M_Mo_120mm_AT_LG - works but haven't worked out the laser designation yet

Sh_155mm_AMOS - works

All the bombs work set high too but they never fall on a direct marker, usually go some 250m away from where they should fall and tried to using Domination artillery system. Always float down away from the marker point, presume velocity and angle?? Going to try to test by setting it towards the marker placed or designation spot.

Cant get M_Mo_120mm_AT / M_Mo_120mm_AT_LG Sh_155mm_AMOS_guided /Sh_155mm_AMOS_LG to work using the Domi system but they as above work ok with create vehicle in the editor?

Hope this helps

Champy

[zapat 56]

Thx for the classes aaand there you go. You guys are right. This is ridiculous.

Comparsion videos:

Red rect is engine controlled object.

Blue rectangle is script controlled object (adjusting g coef of 9,81m/s2 on each frame).

The objects are there, but wouldn't be visible without attached icons.

Release height: 500 m (above player).

Initial horizontal velocity: 50m/2 (180 km/h)

Initial vertical velocity: 0.

This simulates releasing an object above the player from a plane wich is flying level at 180km/h on 500m height.

Objects: waterbarrels. Gravity is okay:

Objects: Bo_GBU12_LGB_MI10 bombs in freefall. Strangely huge lifting effect is added by engine.

The red one could travel hundreds of meters more because it had more time in air. It is not falling: it is gliding.

Edited January 8, 2014 by zapat

[CyclonicTuna 87]

Now all we need is someone who actually has knowledge of real physics and how airborne munitions behave, and who also happens to be a math and coding wizard (not me because I'm lazy and dumb), who would want to properly fix this.

I wonder where we could find such a man.... or woman. I'm not judging anyone.

---------- Post added at 10:40 PM ---------- Previous post was at 10:38 PM ----------

And thanks for the video's to prove my point zapat :)