Occasionally, objects of vastly different sizes get involved in fights. The scale modifier accounts for the fact that bigger items are easier to hit, and usually can take more damage, than smaller ones. There are a variety of ways to represent scale in your game. To get an idea of how to represent scale, see the scale chart:
+96 Small moon +50 Aircraft carrier, Star freighter +46 Jumbo jet, Space yacht +24 Eight-story building +20 Four-story building +18 Very Large Mecha +15 Large Mecha +14 Two-story house +12 Single Person Craft, Medium Mecha +10 City bus, tank, One-story building +8 Elephant +6 Average car, Small Mecha +3 Motorcycle, horse 0 Average Human -3 Human child, guard dog, Rocket Launcher -6 Bread box, house cat, Briefcase, Rifle, Laptop Computer -9 Fashion doll, rat, Pistol -12 Action figure, mouse, Palm computer -18 Plastic army figure, coin, Cred-key -21 Ant, Microchip
Subtract the Attackers Scale from the Defenders Scale. The result is either a positive or negative number. Add this number to the attacker's chance to hit and also add the number to the defenders roll to resist damage.
For example, Joe the street-thug is using a pistol that does 3D of damage and is shooting at a car. Joe has a scale of 0, and the car has a scale of +6. Joe is +6 to hit the car.
However, the car has a body of 2d (it's a clunker), but it gets to add +6 to it's body roll because of its larger scale.
Now, consider what happens if Joe targets the driver of the car instead of the car itself. Because only part of the driver is visible through the back window of the car, the area of the driver that Joe can see will be at scale -3. -3 - 0 = -3, so Joe is at -3 to hit the driver. However because the driver really isn't the size of a guard dog or small child, he does not get a -3 modifier to his roll to resist damage. However, you should apply damage modifiers if Joe happens to hit him in the head.
Weapons also have a damage scale. In many cases this scale is the same as the person wielding the weapon. For instance, a person (scale 0) wields a sword - it will also be scale 0. But if Voltron (scale +18!) wields it's sword, it's sword will also be at scale +18.
Usually there is a discrepancy with powerful ranged weapons. Such as a human holding a rocket launcher. The ammo in the rocket launcher was designed to take out tanks and buildings, so one could give the rocket launcher a Damage Scale of +12. So really we have 2 different scales to compute. The to-hit scale based on size (Defenders Scale - Attackers Scale = Modifier) and the Damage Scale based on actual weapon damage and/or armor of the defender (Defenders Scale - Attackers Scale = Modifier).
Now Joe the thug isn't getting anywhere trying to take out the car with his pistol, so he pulls out a rocket launcher that does 3D damage at +12 scale. The car is at scale 6 and Joe is scale 0. 6 (the car, defender) - 0 (Joe's scale, attacker) = +6, so Joe is at +6 to hit the car with the rocket launcher. 6 (the car, defender) - 12 (the rocket launcher's scale damage, attacker) = -6. The car is at -6 to resist the damage from the rocket launcher - ouch!
Using Dice instead of number ModifiersEdit
If you prefer adding or subtracting dice, simply divide the modifier by 3. This will give you the number of dice. Add the remainder back in. A difference in Scale of +10 is the same as +3D+1.
By using scale modifiers in your campaign, you can create a standard die value for everything "average" in your campaign world. For instance, I like to use 3D for the average in my campaigns, so I set everything up this way:
Average Car: Body 3D (Scale +6)
Average Pistol Damage: 3D (Scale 0)
Average Human Strength: 3D (Scale 0)
Average Raccoon Strength: 3D (Scale -6)
Average House Structural Integrity: 3D (Scale +10)
Assault Rifle Damage: 3D (Scale +6)
With 3D being the average in your campaign, you can easily represent inferior or better objects simply by removing or adding dice to the stat and letting scale take care of all of the other modifiers for you. If I experimented on the raccoon and gave him steroids, he might have a strength of 4D+2 instead of 3D, but the scale will still remain at -6. The extra dice make it possible for the raccoon to hurt a human, but it's not likely that the raccoon, even on steroids, can put a scratch in the car.