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New HE mechanics explained using crude illustrations


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ZverMohnatyj #1 Posted Nov 29 2011 - 04:42

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The patch isn't even out yet and some of the ongoing discussion of this topic is killing me softly.

So because of that, and because we're likely to see a lot more "oh my god, you killed HE! You bastards!" threads - and because the Saints are murdering the Giants, and so I'm starting to lose interest in that game - I thought I'd try my hand at illustrating the "before" and the "after". Note that this is my interpretation of the issue - obviously, whatever internal technical manuals Wargaming is using (if any) probably have a vastly more thorough description. Nor do I claim to have access to a vast hoard of secret knowledge - all of this is drawn from public postings (primarily by the developers on the Russian forums, but I imagine the English-language posts from them - or the Wiki information - should be substantively similarly).

First - the crude, rude, and eye-gouging diagram. [And I can't draw in real life either.] Consider the following "front-side" view of a hypothetical tank (and ignore all the "underscores" - I just need them for spacing):




___________________DEEEEEE
___________________D
_____GGGGGGGGGGGGGGG          
_________________X2D  
___________________DCCCCCC
_________________________C
BBBBBBBBBBBBBBBBBBBBBBBBBB
A
A
A
X1
A
A
A


For simplicity's sake, I've divided this illustration - nifty, huh - into several armor surfaces with made-up values, specifically:

- Surface "A" - front hull, assume 150mm armor. Note the impact point X1.
- Surface "B" - top of the front hull compartment, assume 50mm armor.
- Surface "C" - turret ring and the "underneath" section of the turret itself, assume 10mm armor.
- Surface "D" - turret front slash gun mantlet, assume 200mm armor. Note the impact point X2.
- Surface "E" - turret top, assume 25mm armor.
- Surface "G" - the gun itself (ignored for the purposes of this example).

Got it? Good.

------

Basic assumptions:

- No ricochets, track hits, shells going off into the blue sky, etc. - i.e. "perfectly placed shots".
--- Also note that, per the devs, HE rounds always use nominal armor thickness (i.e. angle of impact does not matter - unlike with AP rounds).

- No penetration (i.e. always use the HE non-penetrating damage formula).
--- For reference, the formula is Damage = (Nominal Damage/2)*(1-Splash/Distance) - Armor Value * 1.3 * Spalling Modifier

- No spalling installed.

- Damage does not diminish with splash radius (not strictly true, but simplifies the illustrative calculations).
--- So the formula is simplified to Damage = Nominal/2 - Armor * 1.3 [This would be effectively the maximum attainable damage in-game - splash equals zero, no spalling.]
--- You can see from the simplified formula that the key variable is the thickness of the armor plate against which HE damage is applied (the thinner the armor, the more HE damage gets through).

------

The Before.

Step 1 - HE round hits the tank.

Step 2 - a sphere equal to the splash radius is generated around the impact point.

Step 3 - the thinnest armor surface within that sphere is what the damage is applied against.
-- Remember that for the purposes of our example, damage is the same throughout the "splash". In reality, damage diminishes (see the full formula above), so it's a combination of "thinnest as adjusted for splash" surfaces. But again - I'm trying to keep things simple here.

Example 1 - HE round impacts at Impact Point X1 (Surface A, 150mm thick). Draw a sphere (a big sphere - but not too big) around that impact point. If Surface B (50mm thick) falls within that sphere, the damage goes against Surface B (50mm). Let's assume the damage is applied against Surface B.

Example 2 - HE round impacts at Impact Point X2 (Surface D, 200mm thick). Let's pretend the gun doesn't exist. The sphere around that point would capture Surfaces B (50mm), C (10mm), D (200mm) and E (25mm). Under the old mechanics, it would be applied against Surface C (10mm).

-----

The After.

Step 1 - HE round hits the tank.

Step 2 - several lines are drawn from the impact point to the nearby armor surfaces. No line crosses "through" an armor surface.

Step 3 - only the surfaces to which an unbroken line can be drawn from the impact point are compared, and the damage goes against the thinnest (or, in reality, "thinnest as adjusted for splash") of these surfaces.

Again. Before, you drew a sphere around the impact point, and every surface within that sphere could be impacted. Post-7.0, you will draw "rays" from the impact point and only the surfaces contacted by "unbroken" rays will count.

So let's reconsider Examples 1 and 2.

Example 1a - HE round impacts at Impact Point X1 on Surface A. Note that there is no way to draw any unbroken lines from point X1 (at least not the way I created the diagram). Thus, HE damage will necessarily be applied against Surface A (150mm), and not Surface B (50mm).

Example 2a - HE round impacts at Impact Point X2 on Surface D. Try drawing unbroken rays from point X2. You can clearly hit Surface D (200mm) and Surface B (50mm). There is absolutely no way to hit Surface E (25mm) or Surface C (10mm). Let's assume that Surface B (50mm) is hit as a result. [Note that if X2 were placed lower, e.g. on the exact "corner" of Surface D, you could theoretically draw an unbroken line to the turret ring, i.e. Surface C. But I've deliberately excluded that possibility from this example.]

-----

Let's review:

- Nothing, and I mean absolutely nothing is being done to the HE rounds themselves.
- Before, you could hit any surface within the splash radius even if you did not have a "line of sight" from the point of impact to that surface.
- Now, you're going to need "line of sight".

And why not throw in a little illustration? Consider three different HE rounds: Shell 1 (250 nominal damage); Shell 2 (500 nominal damage); and Shell 3 (750 nominal damage). I like round numbers, sue me.

Recall that in Example 1/1a (Point X1), under the old system the damage would go against Surface B (50mm), while under the new system it would go against Surface A (150mm). The "old" and "new" final damage values (using our simplified damage formula above) for the three shells would be as follows:

Shell 1 (before) = 250/2 - 1.3 * 50 = 125 - 65 = 60 damage
Shell 1 (after) = 250/2 - 1.3 * 150 = 125 - 195 = 0 damage

Shell 2 (before) = 500/2 - 1.3 * 50 = 250 - 65 = 185 damage
Shell 2 (after) = 500/2 - 1.3 * 150 = 250 - 195 = 45 damage

Shell 3 (before) = 750/2 - 1.3 * 50 = 375 - 65 = 310 damage
Shell 3 (after) = 750/2 - 1.3 * 150 = 375 - 195 = 180 damage

Clearly, it will no longer pay to shoot into the center of a thick vertical armor plate with no "line of sight" to thinner armor surfaces.

Now let's consider Example 2/2a (Point X2). Under the old system, the damage would go against Surface C (10mm) - but under the new system, Surface B (50mm) would be hit instead.

Shell 1 (before) = 250/2 - 1.3 * 10 = 125 - 13 = 112 damage
Shell 1 (after) = 250/2 - 1.3 * 50 = 125 - 65 = 60 damage

Shell 2 (before) = 500/2 - 1.3 * 10 = 250 - 13 = 237 damage
Shell 2 (after) = 500/2 - 1.3 * 50 = 250 - 65 = 185 damage

Shell 3 (before) = 750/2 - 1.3 * 10 = 375 - 13 = 362 damage
Shell 3 (after) = 750/2 - 1.3 * 50 = 375 - 65 = 310 damage

So you can see this is a much better placed shot (under the new system), but the smaller shell is still significantly affected (because it can't "see" the thinner Surface C).

Note that it will probably be a lot tougher to conduct appropriate tests in the field, even in training rooms, because many tanks now have 16 armor surfaces and you have to pick a target where you both know the thickness and the geometrical arrangement of each armor surface. [And geometry matters a lot - Storm literally gave one example, of a HE round impacting the side skirt of a Maus, where if the Maus turns its turret just a little off to the side its thin underside "peeks out" over the impact point and that's where the "damage ray" ends up pointing.] Enterprising players will probably come up with a way to get an approximation, but...well, see the section below.

-----

Tactical implications.

- Where you shoot matters. I.e. you can't just lob rounds into the front hull plate of a Tiger I (Point X1 above) and expect fantastically terrific results. Using HE effectively will now involve things like "bouncing" the splash off the lower edge of the turret (Point X2 moved to the lower "corner" of Surface D, so that it can "see" the turret ring or Surface C) to hit the thinner top armor surfaces - or something along those lines. Obviously, the traditional weak spots for AP shells (e.g. the R2D2 turret on the KV-5) are also good aiming points.

- Small HE rounds care about placement a lot. Big HE rounds care about placement not-very-much. See the examples above - a round with just 250 damage can get completely negated if it hits the wrong surface, whereas a giant ball of explosives from the KV-2's 152mm gun will probably not care a great deal (ok, it will care to some extent, but a significant portion of the damage is getting through regardless, especially once you recall that - once more, with feeling - HE ignores sloping, i.e. tanks like the IS series that rely on sloped armor for survival are particularly vulnerable to well-placed HE shots).

- Side screens will now work wonders. Because a screen will "block" a HE round's "rays" (to the extent that the screen isn't actually penetrated or "destroyed" by the explosion).

- Artillery impact somewhat uncertain. I'm not an experienced SPG driver (a couple of hundred games in the lower-level machines, but not much more). Presumably, top armor hits are going to stay just as effective, more or less; hits that penetrate will definitely be just as effective as before; but splashes near the tank or against, say, a heavily sloped front plate might end up hitting a thick armor surface or else the side anti-HE screens and not doing very much of anything. Tracking, at the most.

So there you have it. Hopefully this is a relatively clear explanation of the matter, at least as I see it. To keep things constructive, please limit the "this sucks! they killed Kenny!" comments to the extent physically possible.

-----

ADDENDUM - clarification of HE internal module damage mechanics. [All sourced from the developer Q&A thread over the past few months.]

Case 1 - HE round penetrates the armor.

- The "point of explosion" is established.

- A sphere is drawn about the "point of explosion" (I think equal to the splash radius).

- Every internal module within the splash radius takes damage from the detonating round.

Case 2 - HE round does not penetrate the armor.

- The game determines which surface to apply the damage against.
-- This is where the "old" and "new" mechanics are utilized.

- The exact point of impact against that armor surface is established.

- A cone is drawn perpendicular to the armor surface with the point of impact as the apex, extending "through" the tank.
-- I believe the cone is established as plus or minus 25 degrees to the line that is perpendicular to the armor surface in question, but am not 100% that this is the exact angle (might be 22.5 degrees, in other words).
-- The "perpendicularity" was confirmed by Storm on a couple of occasions, including in the 0.7.0 Test Q&A thread on November 23. [The specific question was - "is the cone of damage parallel to the 'impact ray' used to determine which armor surface the damage is applied against, or is it perpendicular to that armor surface"; the answer was - "perpendicular".]

- Any internal module within this cone takes damage from the shell, to the extent that said damage is not absorbed by the armor.

In other words imagine a blown-up figure "I<"; the "I" portion is the armor surface; the "cone of damage" extends directly behind that surface through the tank, and any internal module in that cone will take damage.

A final note on external modules. In that same 0.7.0 Test Q&A thread, Storm has stated that, in effect, external modules (i.e. those modules damaging which will not affect the tank itself, like the rangefinder) will be considered separately. So if you have a detonation that can draw an unbroken ray to both an external module and an actual armor surface, the tank will take some damage (modified by the armor surface), and that external module will take some damage (modified by its own armor value).

END ADDENDUM

SHISHKABOB #2 Posted Nov 29 2011 - 04:49

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bump for justice because it's annoying hearing people go "I heard from a guy who said he heard from a guy that they are nerfing X into the GROOOOOUUUUND"

Clockworkred #3 Posted Nov 29 2011 - 05:02

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Thanks for the info, Kurz. At least i know i have to think with my derpguns now.

Pink_Panther #4 Posted Nov 29 2011 - 05:11

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Great post Kruzen - not only did it explain how HE will work, it also made how it currently works clearer (even with your abstract drawing)  :Smile_honoring:

Thanks.

NinjaFisT #5 Posted Nov 29 2011 - 05:12

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Aw, there goes the fun I had with the M4's 105... Good bye excellent derp, I will miss you so. :(

amade #6 Posted Nov 29 2011 - 05:16

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You're always bringing us good, reliable information Kruzenshtern. As a small token of appreciation feel free to use this image for your explanation instead ; )

http://www.amade-wos...ank_diagram.JPG

KillingMeSoftly #7 Posted Nov 29 2011 - 05:31

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View PostKruzenshtern, on Nov 29 2011 - 04:42, said:

The patch isn't even out yet and some of the ongoing discussion of this topic is killing me softly.

You rang?

Thornir #8 Posted Nov 29 2011 - 05:33

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This is excellent OP, thank you!

This illustrates to me that with the usual howitzer "accuracy" well north og .4+, the HE-dependent tanks are going the way of the Dodo. Yes, you can put the m1a1 on the M4. You then have a slower, weaker, slower-firing E8. Useless? No. Worth keeping for credit grinding? Not so much, i am thinking. Same with the Jumbo. The German vehicles that could use the short 10.5 will be impacted likewise, but in my experience, the Hetzer is the only one that carries it often. The KV-2 derp can load AP.

Grinding credits now shifts to the !Surprise! Russian line vehicles with the 107 as a mid-tier weapon I guess...or i could cave and stop trying to be the "Play for Free!" poster child... :blink:

diego999 #9 Posted Nov 29 2011 - 05:34

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Thanks for the info. I was having trouble to understand the new HE mechanics but now you made it clear  :Smile_great:

fuzzylunkinz #10 Posted Nov 29 2011 - 05:39

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View PostThornir, on Nov 29 2011 - 05:33, said:

This is excellent OP, thank you!

This illustrates to me that with the usual howitzer "accuracy" well north og .4+, the HE-dependent tanks are going the way of the Dodo. Yes, you can put the m1a1 on the M4. You then have a slower, weaker, slower-firing E8. Useless? No. Worth keeping for credit grinding? Not so much, i am thinking. Same with the Jumbo. The German vehicles that could use the short 10.5 will be impacted likewise, but in my experience, the Hetzer is the only one that carries it often. The KV-2 derp can load AP.

Grinding credits now shifts to the !Surprise! Russian line vehicles with the 107 as a mid-tier weapon I guess...or i could cave and stop trying to be the "Play for Free!" poster child... :blink:
Yup, 105mm on the M4 simply does not have the accuracy to make use of proper aiming.  Generally you are trying to keep your distance from the tier 8 tanks which means your reticle swallows up the tank, and it's up to the Russian gods to decide where on the tank your nice HE shell will hit.

I foresee myself rebuying the Easy 8.

fatkiddown #11 Posted Nov 29 2011 - 05:41

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Very informative and you get a +1.  Any idea why the change?  From my grey matter, it makes sense.  Thick armor "in the way" of a blast wave _should_ be effective in dampening it....

SHISHKABOB #12 Posted Nov 29 2011 - 05:41

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are we forgetting about the mother of all tier 5 penetrators, the PzIV?

kemzie #13 Posted Nov 29 2011 - 05:55

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Do you guys think that Arty will be affected? My hummel has a blast radius of 3+ meters so it should hit weak spots when hit on top of the tank right? It's not like you can aim for weakspots when using an arty piece.

Otto_matic_Reiffel #14 Posted Nov 29 2011 - 06:01

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The damage makes a lot more sense now, but it does lower HE effectiveness overall. Hopefully they rebalance tanks that rely on HE lobbers for a chunk of their progression (Hetzer and SU-152 come to mind).

Clockworkred #15 Posted Nov 29 2011 - 06:10

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Actually the Shermy has the speed and agility to zoom around bigger tanks and plant one right up their tailpipe, where the armor should be weaker. Although this definitely cripples some derpgun's standoff capability, we're just gonna have to *gasp* think about our shots.

Of course, i'm talking about tanks that have turrets. I don't know about those TDs who don't have that sort of flexibility.

VonKrieg #16 Posted Nov 29 2011 - 06:23

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Auto +1, as always a very informative post by Kruz.

Jeeps_Guns_Tanks #17 Posted Nov 29 2011 - 06:28

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Great post!

amade #18 Posted Nov 29 2011 - 06:31

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How to adapt: If you can't aim at weakspots accurately shoot at the lower sides of the turret or the cupulas if it's big enough. The "rays" from the blast radius will definitely hit the thinner roof armor.

SpectreHD #19 Posted Nov 29 2011 - 06:38

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Accuracy buff for the M4's, Jumbo's and German howitzer 105mm, pl0x? Or at least smaller dispersions...

cv5yorktown #20 Posted Nov 29 2011 - 06:39

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Wow thanks for the great post!

Question: What about modules? Will the module need to be directly impacted by the HE or will a straight line be drawn to it? Also would a module such as a view port count as the weakest point?

Tanks using HE will have to be much more tactical now, but could still be very effective. The main thing I'm looking forward to though is the less splash from artillery.