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Red Orchestra Ballistics

VariousNames

Grizzled Veteran
Aug 6, 2009
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I'm curious as to how the ballistics operate in Red Orchestra.

Here's what I do know. There is projectile drop. The projectiles follow a genuine trajectory which appears to model the acceleration of gravity, i.e. the trajectory becomes more steep with distance.

I also know that penetration chances of armor are affected by distance.

I also know that the game models travel time and that there is no penetration model of static objects and no model for wind drift (the game does not model wind).

What I am curious about is...does the game model air resistance? This can be done in a simplified fashion by enacting one standard model of air resistance for every bullet every time it is fired. However, for a realistic physics engine this has to be simulated to some extent. Air resistance is effectively the friction of projectile ballistics, it acts against the direction of motion and causes the projectile to lose velocity. This effectively means that a given projectile loses kinetic energy, and therefore penetration and power, the further it travels.

A simple way to model this would be by making the damage of a given round decrease over a given distance increment, as well as lose a portion of its velocity at that given increment.

In case you're curious how much velocity it should lose per increment, it is tied to the shape of the projectile in something called "ballistic coefficient." A simple example of how this affects projectiles can be seen with the old 8mm rounds of World War 2 that were round nose as opposed to the "spitzer" rounds seen afterwards....the spitzer rounds, being more aerodynamic, were able to retain a greater amount of their energy over longer distances.

To sum up, what does it model regarding projectile ballistics, and how?
 
What I am curious about is...does the game model air resistance?

To sum up, what does it model regarding projectile ballistics, and how?

Each projectile has a Ballistic Coefficient associated with it. This includes small arms and large-bore weapons.

Code:
class Kar98Bullet extends ROBullet;
....
defaultproperties
{
    BallisticCoefficient=0.390
....
}
 
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Omg, that is amazing, thank you, lol.

I guess that means that projectiles lose velocity over distance? Have any other details you can share about how its calculated? Is there a list of in-game ballistic coefficients?

I'm interested to compare them to real life ballistic coefficients for the projectiles as well....anybody got any sources?
 
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Omg, that is amazing, thank you, lol.

I guess that means that projectiles lose velocity over distance? Have any other details you can share about how its calculated? Is there a list of in-game ballistic coefficients?

I'm interested to compare them to real life ballistic coefficients for the projectiles as well....anybody got any sources?

I seriously doubt the in-game ballistics modeling is particualrly advanced. Is the game really tracking each bullet from a 20 or 30 round burst -- let along 10 or 20 other weapons firing simultaneously?

The BC of a bullet -- excluding it's form factor -- is simple to calculate. Understanding the proper form factor and proper drag function is of course critical to a real ballistic trajectory and real world velocity decay.

But yeah, it would be interesting to hear from those that have played with the game code as to what the in-game BC actually does. :D
 
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I seriously doubt the in-game ballistics modeling is particualrly advanced. Is the game really tracking each bullet from a 20 or 30 round burst -- let along 10 or 20 other weapons firing simultaneously?

Sorry Jeff, you're wrong ;) The in-game ballistics modeling is highly advanced, and does track each bullet, including gravity and drag calculations. One optimization however is that it doesn't do ballistics calculations for rounds fired very short distances where the bullet drop is so negligible it has almost no impact on where the bullet would hit.
 
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I seriously doubt the in-game ballistics modeling is particualrly advanced. Is the game really tracking each bullet from a 20 or 30 round burst -- let along 10 or 20 other weapons firing simultaneously?

The BC of a bullet -- excluding it's form factor -- is simple to calculate. Understanding the proper form factor and proper drag function is of course critical to a real ballistic trajectory and real world velocity decay.

But yeah, it would be interesting to hear from those that have played with the game code as to what the in-game BC actually does. :D
John already answered some of this for you, Jeff... it gave us some headaches when we first introduced the MG42, for sure! In the early days, we had to restrict the weapon mix, including all the high RoF weapons (MG34/42, PPSH etc). A lot of smart optimisation later...

The ballistics calc does pretty much what you'd expect it to: velocity, use the relevant ballistic coefficient to calc the loss in velocity (air resistance, temp, humidity), use that information (and gravity) to figure out the drop. We don't play with the odds and sods such as coriolis effect, as the impact (pun unintended) is very small at the engagement distances we are normally dealing with.

As for calculating the ballistic coefficient: can be a bit of a nightmare, as it is very hard to either find the relevant (1940s) data, or to find the relevant ammo. We have the weapons, plus modern ammo for them - but I am wary of relying on modern test data to derive the BC from. Drag function is a lot easier :)

We'll see where we get to with the new game... we may just need to concern ourselves with the more extreme effects. But I can live with us being an inch off at 1,000 meters! Mind you, I was rather pissed yesterday in the play-test when one of our guys shot me with a pistol at just over 100 meters... "I just sort of aimed a couple of feet over his head...". Bugger.
 
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That is astonishing... I'm really impressed with the depth of your ballistics model.

Two questions, however...noting with sympathy how hard it is to find ballistics data for WWII cartridges. What ballistics model variables are being used for each projectile (I understand if this is trade secret, I'm interested for the sake of my gameplay)? What sources are you relying on for these variables? Books, documents, websites...for research purposes....

Finally, at what range does the trajectory model begin to be calculated? 100 meters? Less?

Thank you.
 
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Sorry Jeff, you're wrong ;) The in-game ballistics modeling is highly advanced, and does track each bullet, including gravity and drag calculations. One optimization however is that it doesn't do ballistics calculations for rounds fired very short distances where the bullet drop is so negligible it has almost no impact on where the bullet would hit.

Thnx :D that's infinitely more than I have been able to drag out of others who are routinely looking at the games code.

Are you using Siacchi, or drag functions and finite difference calculations to accurately model Vdrop and trajectory? I presume you are not employing simple kinematics and vacuum trajectory?

Somebody above posted an in-game BC for spitzegeschoss fired from a 98K. for my own edification, what form factor did you employ to determine the above listed in-game BC -- I mean this in terms of the bullets real world BC. I suppose it might also be interesting to compare in-game Vdrop of the same bullet to both finite difference methodology and actual schusstafeln.

What is the cut off range -- I mean the short range you are referring to where vdrop and bullet drop calcs are deemed superfluous?

Best Regards
Jeff
 
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John already answered some of this for you, Jeff... it gave us some headaches when we first introduced the MG42, for sure! In the early days, we had to restrict the weapon mix, including all the high RoF weapons (MG34/42, PPSH etc). A lot of smart optimisation later...

The ballistics calc does pretty much what you'd expect it to: velocity, use the relevant ballistic coefficient to calc the loss in velocity (air resistance, temp, humidity), use that information (and gravity) to figure out the drop. We don't play with the odds and sods such as coriolis effect, as the impact (pun unintended) is very small at the engagement distances we are normally dealing with.

As for calculating the ballistic coefficient: can be a bit of a nightmare, as it is very hard to either find the relevant (1940s) data, or to find the relevant ammo. We have the weapons, plus modern ammo for them - but I am wary of relying on modern test data to derive the BC from. Drag function is a lot easier :)

We'll see where we get to with the new game... we may just need to concern ourselves with the more extreme effects. But I can live with us being an inch off at 1,000 meters! Mind you, I was rather pissed yesterday in the play-test when one of our guys shot me with a pistol at just over 100 meters... "I just sort of aimed a couple of feet over his head...". Bugger.

hi Alan:

i agree that accurate vdrop is of little interest in small arms and infantry combat in terms of wound ballistics. and of course anyone who has done a bit of real world exterior ballistics numbering crunching will know that real world bullet drop can be calc'd independently of vdrop. however if you are interested in material penetration capability of ball or armor piercing small arms ammunition -- like shooting someone through a fence or drywall or CMU or logs or whatever -- than Vdrop and resultant kinetic energy at impact and residual kinetic energy following rear surface passage is obviously essential to any real world calcs. but again, if your sole interest is wound ballistics, operational studies of modern infantry combat suggest engagement ranges in excess of 100-yards are rather rare. any impact velocity within this range from a bullet fired from from a typical infantry rifle, SMG or MG of this era will put you well above the critical impact energy required for an incapacitating wound.

vdrop is also essential in realistic fragmentation models and associated wound capability. shell fragmentation experiences huge levels of drag and therefore looses both material penetration capability and wound capability pretty rapidly from the point of burst (depending of course on fragment size). joint munitions effects fragment models are probability based. fragment density vs. target size\target exposure. either you are hit with a fragment, or you are not. the fragment either does, or does not have sufficient residual velocity to inflict a wound. hit point decay vs. distance from burst should go the way of the dodo.

reasonably accurate vdrop calcs are also important to: canister effectivness; shrapnel shells (still in common use in the Soviet Army in WWII); and material penetration models.


class Kar98Bullet extends ROBullet;
....
defaultproperties
{
BallisticCoefficient=0.390
....
}

edited to add the above posted fluctuating BC value.
 
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Damn, you get technical fast :)

The straight answer is "can't even remember"... we implemented the ballistics calcs a very long time ago - somewhere around 2003. As to who's equation - honestly can't remember where we grabbed the beast from. I'll have to go hunting way back through notes for it.

No, it doesn't assume a vacuum and gravity alone... atmospheric density, drag co-efficient plus the round's BC. For drag we use the G1 curve (from memory), so it gives suitable results in the transonic range. BC we get wherever we can find it, test the given in the data and then match to empirical data we can find to cross-check it.

We don't model anything extra about rounds de-stabilizing in flight or any other odd effects. I can't remember offhand how we handle wounding, but I seem to remember velocity DOES come into it (or maybe that is in RO2) - not really relevant, as you said, to rifle rounds - but it is relevant to pistols etc.

Likewise on penetration - the round will lose a chunk of velocity/energy... which is important to know about!
 
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Damn, you get technical fast :)

The straight answer is "can't even remember"... we implemented the ballistics calcs a very long time ago - somewhere around 2003. As to who's equation - honestly can't remember where we grabbed the beast from. I'll have to go hunting way back through notes for it.

who's equation -- hmmm? I don’t get it. it's an iterative process. in actual trajectory and vdrop calcs you are having to solve multiple equations simultaneously for each increment of the trajectory being assessed. drag is not a constant -- it varies with velocity -- or mach number if you like.

finite difference calculations or Siacci calcs are rather laborious for any one who has actually had to cross check spreasheets or programers output by hand calculations (like me). it's why I find this all rather fascinating given the number of calculations required to assess a single bullets trajectory and vdrop in a realistic manner let alone a 20 or 30 round burst entering a virtual environment.

g1 is fine. infact Sierra swares by it and tweaks the form factor or varies it as well to force fit the curve around empirical data for their bullets. but g1 looses it's shimmer when assessing many larger caliber projectiles of the period because of boattails, conical windscreens and etc but I suppose if in-game ranges are kept down to R<400 or 500meters for large caliber fire or say R<100meters or less for small arms, the differences are relatively unimportant. if on the other hand you slap a 130000UU endfog distance on a map such as Krivio Rog (spelling?) than the differences between g1 and g6 become much more influential on vdrop (impact velocity) and projectile drop (this equates to both: "realistic" correlation between gunsight picture and projectile drop as well as a very crucial effect upon "realistically" simulating battlesight gunnery for both small arms and large caliber weapons).

since this is all old hat what are the in-game vdrop values and bullet drop for say the above spitzer? It sounds like from your description that the in-game ballistics modeling is something simplified -- solving a single equation for extended trajectory and incremental vdrop(?). It would be interesting -- at least for me to cross check the ingame performance vs. actual schusstafeln and actual finite diff calcs.
 
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Actually, you've raised an interesting point that I'll need to check out (when I have time): checking out the longer distances. With RO2, the effective range may be somewhat longer. I have to admit I've never worried too much about it over 3-400 meters in the past. Might bear some scrutiny...

The calcs run (very roughly, cos I am spitting this one out from memory) like this: for each increment, you have a starting velocity, location and vector for the projectile - obviously starts at the basic muzzle velocity. Starting velocity gives the (G1) drag coefficent for that increment, as that varies with velocity; you already have the BC, along with the relevant air density/humidity/temperature (we treat these as constant in RO1 - might even allow that to vary in RO2); now it becomes a straight calculation for that increment to give the loss in velocity, therefore loss of altitude/change in vector. Gives a final velocity, location and vector for the projectile. For the next increment, take those as the starting input, rinse and repeat.

Again from memory, the "increment" is one server tick - say 1/25 of a second, but ask a techie for a real answer on that one... And I think we draw a straight line from start point to end point of the increment, to see if the bullet would have passed through anything, hit detection etc...

And, beyond all that, we get back to the point of "just how accurate does the model need to be?". For our purposes, it needs to be "close enough". If we've introduced an error of 5-10%, I'm not going to worry, frankly... you'd have to be on a real-life target range, under ideal conditions, with a good shooter, to spot the difference. One of the key elements in a "simulation" like RO is that the thing is consistent and performs enough like the real world. Actually, it is probably TOO consistent, as we don't allow for variation in the production quality of the ammo or the guns, never mind wear and tear, poor maintenance and all the rest - that stuff may have to wait until RO2 :)

Hey Alan:

thanks. that sounds much better. you must have gotten a cup of tea into your system after your previous post? :D

but what is cut-off distance that Jager-Ramm was going on about? where are you actually tracking in-flight characteristics and where are you ignoring them? 1-meter -- 100-meters?

in addition, would you indulge me with an example of in-game in-flight tracking? any bullet or projectile will suffice. i just need the in-game bullet used, it's ingame BC, and incremental Vdrop and bullet drop values determined from the game. I suppose I can back out in-game projectile drop using tank sights for larger projectiles (i cant do it for small arms as I cant accurately control initial launch angle). And using the tank sights assumes the launch angles for various range settings correlate to real world super-elevation settings. I suppose I could really wig out and use a stop watch to calc flight time over longer flight distances and subsequently back-calculate Vdrop. But the actual game output would obviously be far more interesting to mull over. and this isn't anything I am hoping to try and bust your balls with later. in fact i won't even do a follow-up post here or any other forum on the subject. I’m more interested with game\simulation evolution (not RO per say). I'd like to compare the in-game flight data output with actual exterior ballistics algorithms and firing tables – for my own edification. Danke.

Jeff
 
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Einsten2.jpg


Fortunately that some people can understand what you say guys!
Because I can't...
 
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Hey Alan:

thanks. that sounds much better. you must have gotten a cup of tea into your system after your previous post? :D

but what is cut-off distance that Jager-Ramm was going on about? where are you actually tracking in-flight characteristics and where are you ignoring them? 1-meter -- 100-meters?

in addition, would you indulge me with an example of in-game in-flight tracking? any bullet or projectile will suffice. i just need the in-game bullet used, it's ingame BC, and incremental Vdrop and bullet drop values determined from the game. I suppose I can back out in-game projectile drop using tank sights for larger projectiles (i cant do it for small arms as I cant accurately control initial launch angle). And using the tank sights assumes the launch angles for various range settings correlate to real world super-elevation settings. I suppose I could really wig out and use a stop watch to calc flight time over longer flight distances and subsequently back-calculate Vdrop. But the actual game output would obviously be far more interesting to mull over. and this isn't anything I am hoping to try and bust your balls with later. in fact i won't even do a follow-up post here or any other forum on the subject. I
 
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Don't e-mail the answers, I want to see them :mad:

They should be public knowledge :p I suggest that they should be included in the game manual in some form of fashion. If the exact model number of the AP projectiles should be included in the Ost menu along with piles of ballistic data, I beg of you to include BC to help us predict trajectories in long range shots.

Often I find myself wondering exactly how to predict the arc of my projectile, perhaps most importantly how much to lead, and this causes issues when firing a bolt action over long distances.

Damn, you get technical fast :)

The straight answer is "can't even remember"... we implemented the ballistics calcs a very long time ago - somewhere around 2003. As to who's equation - honestly can't remember where we grabbed the beast from. I'll have to go hunting way back through notes for it.

:D

RGR. Is it a copy-and-paste deal to HoS or do you have those notes available to you?

Sorry to be such an ***hole, I was just wondering. I have an unhealthy fascination budding over ballistic coefficients and trajectory modeling.

Likewise on penetration - the round will lose a chunk of velocity/energy... which is important to know about!
:eek:

/exalt

I'm interested to know, now, how this affects static object penetration in HoS....but I won't press that issue. I know its eh secret. Going to be a very interesting mechanic if it has even a remote portion of the complexity of your human internal ballistics models and airborne freefall ballistics.
 
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I love the ballistics in this game, but at the normal distances the huge bullet weight and power of those rifle cartridges (7.62x54R and 7.92x57) mean that under 250m bullet drop and air resistance is negligible...
Only in really big maps like Barashka it can be noticed...
For SMG the problem above 150m is so big that it is also difficult to hit anything...
Tank bullets have nice ballistics also...
 
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