Tuesday, September 24, 2013

Redefining range


As I moved from bow and arrow to long range rifles I carried over a mistake. The naked eye can't see well at the still effective ranges modern machine guns and rifles have. The classic increasing "to hit" penalty by range is not a good model anymore.

If I do a gradual drop in precision over range when using an iron sight the weapon becomes too deadly because I'm not taking into consideration the much faster drop introduced by the shooter's eye. There's a gradual loss in precision due to the weapon's craftsmanship and ammunition properties, but there is a much larger drop in precision due to the naked eye's ability to distinguish a target.

This calls for a separation of modifiers. One for the weapon's range performance (which may vary with ammunition type too), and another for the visual capacity of the shooter (which may be enhanced through optics).

I could factor in the optics into a single modifier to the weapon, but that brings two problems. I'd have to write weapon stats for each type of optic device: reflex, holographic, and scopes by amplification (3x, 4x, ... Nx). This also makes Joe "Carnival" Sniper quite good at shooting with a sniper rifle. He just picks up one with a 9x scope and fires away. But it takes more skill than that to use a sniper rifle at those ranges and I want the game to represent it. I'm even thinking about making the sniper character require a well trained player. It takes a bit more to play a sniper and I feel will be a gratifying feeling for the players masters the sniper as a character class. More on this to come in my next post, Designing the Sniper.

Now back to weapons and the crunchy part of this idea.

Usually weapons have a range modifier based on distance, but no sight modifier. That is, a modifier that adjusts for the attacker's ability to pinpoint the target. A weapon may have a huge range and standard modifiers would add values for different ranges up to the maximum effective range of the weapon. For example 0 at short range, - 1 at medium range, - 3 at long range, etc. This works well with bows, their range limit is within visual range of the naked eye. Firearms on the other hand have ranges that exceed the naked eye's capacity to distinguish things and thus aim correctly. So a weapon, if equipped with basic iron sights, will become ineffective at hitting a bull's eye a lot sooner than it stops being lethal or precise. In other words at 400 m the bullet is still flying pretty much where the sight said it would, but the eye can't pin point the target as well anymore and be precise in the alignment between target and sight. Image amplification is needed.

An error I believe I'm borrowing from other games is taking the range penalty to include both weapon precision and shooter sight. Sight, I believe, should be a penalty applicable based on the character skill and the optics being used, not the weapon's quality. It applies to a human's eye and in the case of fantasy settings it could be modified by race too.

Currently I'm using one modifier for range, the weapon's. But this makes modeling difficult because iron sight weapons seem to be too deadly at ranges where the target could hardly be seen with the naked eye. Optics add benefits to the weapon's effectiveness when in truth they should add better "aim" to the shooter. There are two values so to speak: the weapon's ability to shoot straight and the shooters ability to make use of this precision.

Normally the weapon's quality and ammunition drift in flight lead to the range modifiers. For example: point blank, short, medium, long and extended range all add increasingly negative modifiers due to bullet drop, wind, bullet spin and barrel craftsmanship. Usually with bows dexterity and fighter skill add in the bonuses to compensate for range. In the case of modern weapons optics also add in a modifier by adding image amplification and improving aim.

The option of separating them into to values may be questionable, specially since it adds another value to consider when resolving combat. Yet I believe it simplifies the weapon and sight models considerably and makes skill even more relevant and also easier to implement.

Here's a comparison between both models:

Classic range model

A weapon, say an AK-47 has different ranges: point blank (20 m), short (80 m), medium (200 m) and long (400 m). These are examples and not meant to be based on the real weapon. The modifiers are as follows: 0, -2, -5, and -7. A scope adds a +3 modifier, or for a more detailed model: + 4, + 3, + 2 and + 2 according to each range bracket.

This a simple and quite common and easily understood model, but it has its flaws. What if the weapon is precision manufactured? Will the penalties be less? Why? At long range the error introduced by the naked eye is more than any benefit in better craftsmanship. At 300 or 400 meters the target is so small it is hard to make a precise aim with just an iron sight.

Now the scope gives a flat + 3, or in the more detailed model a succession of values depending on range. Will this be so for weapons that have an effective range of 400 m as those that have an effective range of 800 m? Why? Scopes bring things closer, but something 800 m is still twice as far as 400 m and shouldn't get the same benefit.

Even with the improved model with a modifier for each range, what happens when the same scope is fitted on another weapon that has different ranges? For example point blank (30 m), short (120 m), medium (300 m) and long (600 m). Does it improve it just the same? Why does this weapon get a + 3 at ranges up to 120 m when the AK got + 3 only up to 80 m? What happens the other way around when the weapon's range decreases?

What about skill? Putting a scope on a sniper rifle does not a partisan a marksman make. Really long range rifles are usually trimmed for a distance and quick adjustments outside its set range setting are slow to do and require skill and preparation. That is why the scope have mil marks that help to compensate quickly, but even then there is a limit. Modeling this with a classic range and scope model is difficult. The scope is effective up to 2000 meters, but at any one given moment the sweet spot is plus/minus 100 or 200 m.

Range and sight model

Now let's look at it as two separate and overlapping modifiers. One is sight and the other is weapon precision. Weapon precision is how good a weapon performs at a given range. It is similar to the classic model of range modifiers. Let us assume for the moment that there are three ranges: short, medium and long. These ranges have modifiers depending on weapon quality and they drop of gradually or harshly depending on weapon type. For example : 0 , -1 and -3 for a rifle. The ranges for the rifle are short 50 m,  medium 150 m, long 300 m.

Weapon Modifiers
50 m : 0
150 m : -1
300 m : -3

Sight modifiers on the other hand are fixed by the human eye. For example 0, -3, -6, -12 for ranges of 50 m, 100 m, 150 m and 200 m. When using the weapon the modifiers add up.

Sight Modifiers
50 m : 0
100 m : -3
150 m : -6
200 m : -12

At 40 m the modifier is 0, 0 from rifle range and 0 from sight. At 120 m the modifier is -7, -1 from rifle range and -6 from the sight modifier. At 180 m the modifier is -15, -3 for rifle range and -12 for eye sight. As you can see the weapon quickly becomes ineffective at such ranges, but the weapon model is still simple and not affected by optics.

Now let's put a 3x ACOG scope on the rifle. The magnification means everything seems closer to the shooter's eye, but only to the eye not the weapon. The bullet still has to travel the full length of the distance to target and weapon craftsmanship and ammo selection plays a huge role here. The target at 40 m is now apparently 13 m away, the target at 120 m is now apparently 40 m away and the target at 180 m is now apparently 60 m away. This improves the sight modifier greatly as these are taken at the apparent distance not actual distance. The weapon's modifiers are still taken at the real distance to target. Taking the same modifiers as the previous example:

Weapon Modifiers
50 m : 0
150 m : -1
300 m : -3

Sight Modifiers
50 m : 0
100 m : -3
150 m : -6
200 m : -12

The examples convert to:

40 m : 0 modifier before, now apparently at 13 m, 0 modifier now : 0 for weapon range modifier (use real distance of 40 m) and 0 for sight modifier (use apparent distance to target of 13 m)

120 m : -7 modifier before, now apparently at 40 m, - 1 modifier now : -1 for weapon range modifier (use real distance of 120 m) and 0 for sight modifier (use apparent distance to target of 40 m)

180 m : -15 modifier before, now apparently at 60 m, - 6 modifier now : -3 for weapon range modifier (use real distance of 180 m) and -3 for sight modifier (use apparent distance to target of 60 m)

Notice how effective adding 3x amplification was to the weapon's performance. The shot at 120 m got a seven fold improvement and the shot at 180 m nearly a three fold improvement.

This mechanism adds complexity because it requires another value to add when calculating modifiers, but it simplifies weapon modeling as a whole. As you can see the rifle is still the same and the player doesn't have to deal with lots and lots of weapon stats, each for a different attached scope. The weapon is one thing and the scope is another and they're now easily combined.

Next post will cover the sniper and his rifle in more detail.


Image source
http://www.archivio.aria.compressa.org/gallery/lst_image.php?pid=760&size=fullsize
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