Before we move into the mechanics, a bit of explanation about the penetration values used in World of Tanks. Germans and Russians tested their guns in different manners. Both used different armor, armor densities, and angle of attack. Also, the Russians required a higher standard of guaranteed shell penetration. Here is what Overlord says about penetration values.
”{Abbreviations expanded and spelling corrected} "In-game, we use the Soviet penetration system with 0 (90) degree armor slope and 75% guaranteed shell penetration (which is more than the 50% guaranteed penetration used in German penetration system). That's why German guns have, as you say, deflated stats in-game.” 75% guaranteed shell penetration is defined as “75% of shell splinters behind the test target”.
“The way we calculate pen data for German guns is the following:”
- German penetration data - 30 degree penetration data (the most common) is converted into 0 degree German penetration data.
- 0 degree German penetration data is converted into Soviet 0 degree data.
- the outcome is usually quite close to 30 degree German penetration data.
This means: in general, German 30 degree armor slope penetration data is equal to 0 degree Soviet penetration data (because of guaranteed penetration gap).
The main difference lies in guaranteed penetration coefficients, which are lower in German systems. NOTE: There are also a few minor game balancing tweaks, so not every conversion is perfect.
NOTE: The collision model to calculate hits is a simplified version of the tank, so its possible there are some superficial areas where a
shell can pass right through without hitting anything.
Update: Wargaming should breakdown how they converted from other nation's penetration tests to the game standard on the forums at some point.
Penetration Mechanics
Once you have hit the enemy, the game then calculates where the shot hit the enemy, at what angle you struck the armor, the effective thickness of the armor (based on the angle), speed, width, and weight of the shell, whether you penetrated the armor, and if so, what was in the path of your shell after striking the armor. A shell can indeed pass clean through a tank.
Note that shell speed falls with distance traveled and thus, AP ammunition can get significant reductions in penetration when firing at distant targets. HE ammunition penetration is not affected by distance.
- At 100m - gun has 100% penetration (+/- 25% random)
- At 500m - approx -20% to -25% to it's penetration value (varies based on the exit velocity of the shell from the gun).
- With distance, from 100m to 500m, penetration degrades linearly.
If all the above was not enough to calculate, Penetration value varies every time you fire your gun. This variation can be up to a 25% plus or minus penetration value and is based on a Gaussian (normal) distribution curve. Shell Damage also varies in the same manner.
Shell Normalization
When a shell hits armor, and if it does not bounce/ricochet, it will dig in and try to penetrate at a 90 degree angle. Typically, it only increases the angle of attack by about 10 degrees.
Overmatch -- Shell Size
In WOT, overmatch is currently modeled so that when the caliber of the weapon is 3 times greater than the thickness of the armor, than overmatch (no chance to ricochet) occurs.
Overmatch -- Penetration
Wot adds an additional version over overmatch based upon when the shell's penetration is more than 2 times greater than the thickness of the armor. When this occurs, shell normalization is increased by an undisclosed amount.
Chewie, on the WoT forums, made a good post about penetration.
Penetration is such a huge aspect to World of Tanks, that I think there needs to be a little more light shed on the topic. From what I understand (and is confirmed by Overlord), these are the six variables that are included in calculating penetration:
- - Shell penetration statistic
- - Shell penetration variation
- - Shell normalization
- - Distance to target (range reduced penetration)
- - Thickness of target's armor
- - Angle of incidence to target's armor
So, every time you fire a Shell at a target, the server does the following five calculations:
Angle of incidence Angle of incidence can also be written as 90 - angle to the horizontal. Since few of us are math majors, I'm going to reverse the calculations so that 90 degrees is a T angle penetration (90 degrees is thus the best angle and 0 is the worst). I will call this the
attack angle.
Ricochet Simplification The projectiles and the angles of impact are idealised, to make calculations less complex. Every angle of impact lower than 20 degrees counts as a ricochet! (10 degrees plus the 10 degree shell normalization). With one exception: If caliber of the projectile is three times greater than the armor and the angle is greater than 8 degrees, the shot will penetrate. All shells have a ricochet value and an idealization value. These are 20 and 8 degrees, for the most part, of the shells.
- Check for ricochet. If your attack angle is lower than 10 degrees (or, in other words, almost parallels the armor), your Shell will ricochet and you will not penetrate. If your Shell size (in mm) is at least three times the amount of armor (in mm) you are attacking, your Shell will not ricochet (unless angle is less than 8 degrees). If your Shell's penetration (in mm) is at least two times the amount of armor (in mm) you are attacking, your Shell will not ricochet (unless angle is less than 8 degrees).
- The Shell is normalized to the center line. When a Shell first comes in contact with armor, it will screw itself somewhat into the armor. This action increases the angle of attack, as the Shell tends to "right" itself towards a right angle (90 degrees) to the armor. Each Shell has a different value of normalization, but it normally increases the attack angle by 10 degrees.
- Calculate thickness of armor. The minimum armor thickness is the tank's section of armor that you are hitting. If there is an attack angle to the shell, due to armor slope and/or angle from which you fired at the target, this increases the armor thickness that your Shell has to penetrate. For a more thorough explanation (and very helpful picture), see here.
- The basic formula for LOS (line of sight) armor is: LOS armor = base thickness / cos(angle of incidence){ed note: this formula not reversed}.
- Remember that for an attack angle shot (where 90 degrees is a straight side shot), the formula is effective armor = base thickness / sin (attack angle).
- Also note that in Excel (which uses radians, not degrees), the formula would be effective armor = base thickness / sin(Radians(attack angle).
- Armor with with a 30 degree slope would be effective armor = base thickness / cos(sloop angle) {Slope angles are typically not reversed. Thus, a 30 degree slope provides better protection than a 60 sloop}
- Calculate penetration value of the shell. The base stat of your tank's gun and Shell are used as the basis for this calculation. The distance between you and the target is also considered. At 100m, you will have 100% of your Shell penetration, but this decreases linearly down to 80% at 500m. Next, the penetration value is modified by Gaussian distribution with an upper limit of +25% and a lower limit of -25%. In other words, your Shell may have an actual penetration value of 75% - 125% of the displayed value (without range figured).
- Compare the calculated penetration value to the calculated thickness of the armor. If the penetration value is larger than the thickness value, you penetrate and deal damage.
Penetration Multipliers
90 1x 80 1.02x 70 1.06x 60 1.15x 50 1.31x 40 1.56x 30 2.00x 20 2.92x 10 5.76x 5 11.47x The table to the right gives the effective armor increase multiplier for the Attack Angle and the armor slope (the angle from the flat horizontal), so straight up and down armor would be 90 degrees and a multiple of 1, and thus no increase in the effective armor.
EXAMPLE 1:
You fire a Shell with 100mm of penetration at a target 500m away. The target is at a 90 degree attack angle to you, and his armor is not sloped with a thickness of 75mm. Let's go through the steps.
- Check for ricochet. You are at more than an 10 degree attack angle. No ricochet.
- Shell is normalized. The target is at a 90 degree angle to you, so the Shell does not need to normalize.
- Calculate thickness of armor. The target is at a 90 degree angle to you, so 75mm / cos(0) = 75mm
- Calculate penetration. Your base penetration stat is 100mm. You are at a distance of 500m. So, our adjustment for distance leaves us at 100 * 80% = 80mm penetration. With the Gaussian distribution, our Shell may have a penetration value of 60mm to 100mm.
- Compare penetration to thickness. Our penetration value lies within 60mm - 100mm versus 75mm armor. We have a very-high chance of penetrating.
EXAMPLE 2:
You fire a Shell with 100mm of penetration at a target 300m away. The target is at a 45 degree angle to you, and his armor is not sloped with a thickness of 75mm. Let's go through the steps.
- Check for ricochet. You are at more than a 10 degree attack angle. No ricochet.
- Shell is normalized. The attack angles is increased by 10. Target is at a virtual 55 degree angle to you.
- Calculate thickness of armor. Virtual armor = 75mm / cos(35 degrees). The 35 degree is the angle of incidence calculated from the angle of attack in step 2 (90o - 55o = 35o). The result is 91.5mm.
- Calculate penetration. Your base penetration stat is 100mm. You are at a distance of 300m, which is halfway between 100m (full penetration) and 500m (80% penetration). So, our adjustment for distance leaves us at 100 * 90% = 90mm penetration. With the Gaussian distribution, our Shell may have a penetration value of 67.5mm to 112.5mm.
- Compare penetration to thickness. Our penetration value lies within 67.5mm - 112.5mm versus 91.5mm. We have a slightly-less than average chance of penetrating.
EXAMPLE 3:
You fire a Shell with 100mm of penetration at a target 100m away. The target is at a 45 degree attack angle to you, and his armor has a slope of 30 degrees from the vertical with a thickness of 75mm. Let's go through the steps.
- Check for ricochet. You are at more than a 10 degree attack angle. No ricochet.
- Shell is normalized. The attack angle is increased by 10. Target is at a virtual 55 degree attack angle to you and a slope of 20 degrees.
- Calculate thickness of armor. Virtual armor = 75mm / cos(35 degrees) / cos(20 degrees). The 35 degree is the angle of incidence calculated from the angle of attack in step 2 (90 - 55 = 35 degrees). The result is 97.4mm.
- Calculate penetration. Your base penetration stat is 100mm. You are at a distance of 100m, so our adjustment for distance leaves us with full 100mm penetration. With the Gaussian distribution, our Shell may have a penetration value of 75mm to 125mm.
- Compare penetration to thickness. Our penetration value lies within 75mm - 125mm versus 97.4. We have a more than average chance of penetrating.
I hope that clears up any questions you may have about penetration. If not, post away!
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