What reduction in silhouette associated with going hull down ?

Degrees of Frost · January 9, 2001

My understanding is that silhouette represents, roughly, the size of an AFV and is therefore plays some role in determining "to hit" percentages for guns engaging this AFV (but I admit that I am unsure as to how "to hit" percentages are calculated).

Is silhouette reduced when a vehicle is hull down ?

If so is this reduction uniform for all AFVs that are hull down ? I would imagine that that the reduction would have to vary somewhat - a tank like a Sherman would "shed" alot of silhouette when it goes hull down and become harder to hit than usual - while an assualt gun, like say a Hetzer or a JdpZ IV, couldn't lose as much silhouette and still be able to keep it gun in play.

edited to remove extraneous bits and pieces and I am now fully recovered

[This message has been edited by Degrees of Frost (edited 01-19-2001).]

Lt Bull · January 9, 2001

My analysis of the basic quoted To Hit % values in CM indicates that being hull down relates to roughly a 37% reduction in target size.

I am curious to hear other peoples findings/conclusions and see how this might correlate to the actual figure (or model).

Lt Bull

Jeff Duquette · January 9, 2001

I dunno the ins and outs of how its modeled in the game. Basically a tank manuvers itself adjacent to a crestline in such a way that is hull is covered\protected from shots fired at the tank, but the tank can still peak it barrel over the edge of the crestline and fire at bad guys. There is apparently some game controversy with respect to the benifits of being hull down when your being fired at.

I'm more of a visual guy...heres a picture that might help you. From: W. Schneider's "Panzertaktik".

Degrees of Frost · January 10, 2001

<BLOCKQUOTE>quote:<HR>Originally posted by Lt Bull:

My analysis of the basic quoted To Hit % values in CM indicates that being hull down relates to roughly a 37% reduction in target size.

I am curious to hear other peoples findings/conclusions and see how this might correlate to the actual figure (or model).

How did you carry out this analysis ?

Was this stated 37% reduction in size common for all hull-down AFV's ?

What does the reduction in size have on the "to hit" chance of engaging guns ?

I guess the third question is the most important one.

<BLOCKQUOTE>quote:<HR>Originally posted by Jeff Duquette:

I dunno the ins and outs of how its modeled in the game. Basically a tank manuvers itself adjacent to a crestline in such a way that is hull is covered\protected from shots fired at the tank, but the tank can still peak it barrel over the edge of the crestline and fire at bad guys. There is apparently some game controversy with respect to the benifits of being hull down when your being fired at.

I think I understand the concept of being hull-down, though I rarely get my tanks into good hull down positions - but pictures are always fantastic.

I believe that hull-down in CM is all or nothing, either the AFV is hull down or it isn't. My understanding is that there is no "degrees" of hull-down.

I think I have read a thread [threads ?] where the benefits of being hull down were debated. I think the mixed blessings of being hull down for the Mk IV or was it the Mark VI was discussed at some length. It becomes a question of weighing the benefit of reducing engaging tanks "to hit" chance versus increasing the probability of successful incoming shot hitting a weaker part of the tanks frontal aspect (the turret in the MkIV example).

But, again, if memory serves the reduction in the "to hit" chance wasn't really focussed on. It came down to more of a discussion of the benefits of being hull down in the more abstract. Increased chance of retreating out of enemies LOS, being able to retreat and move about unobserved, and of course reducing the "to hit" - but by how much ? and is the reduction the same for all hull down AFV's ?

[This message has been edited by Degrees of Frost (edited 01-10-2001).]

Lt Bull · January 10, 2001

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

How did you carry out this analysis?

Firstly I assumed a statistical normal distribution to model shot dispersion as a basis of the study and also (very importantly) guns ALWAYS target the CENTRE of the target visible to them.

I then recorded the quoted "To Hit%" of various guns vs various targets (silhouettes) both "hull down" and "in open" at various ranges (500,1000,1500,2000,2500m) given on a CM scenario editor firing range.

From this data, for each range, for targets "in the open", an arbitrary (but nevertheless valid) STANDARD DEVIATION (or standard measure of shot dispersion) can be subscribed to each type of gun BASED on the "To Hit%" and target silhouette.

Once this STANDARD DEVIATION of shot dispersion is determined for the gun at that range, it is possible to look at the "To Hit%" against the same target at the same range but when the target is now "hull down" and determine what % reduction in silhouette would be associated with the new hull down "To Hit%".

note: I assumed that silhouette varies linearly so that a silhouette of 100 is twice the size/area/target of a silhouette of 50 for example. (important: this does not imply that a gun has double the the chance of hitting a target that has double the silhouette at the same range!)

I was going to post some graphs/pictures/tables to better explain but gave up after I realised you cant cut/paste BMP/JPGs to Forum threads. Files need to be hosted online somewhere and then linked to those sites.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

Was this stated 37% reduction in size common for all hull-down AFV's ?

My analysis concluded that a 37% reduction in target size (or silhouette) when hull down is consistent for all vehicles regardless of size/silhouette.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

What does the reduction in size have on the "to hit" chance of engaging guns ?

I'm quite sure the modelling of hits vs guns is handle differently than hits vs vehicles as there appears to be no silhouette value for guns. Regardless, if you think about it, guns are in effect like a tank's turret, so they can be considered in some ways as a tank in constant "hull down" status (with only the turret exposed). Further, HE is primarily required to KO a gun, not AP.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

I believe that hull-down in CM is all or nothing, either the AFV is hull down or it isn't. My understanding is that there is no "degrees" of hull-down.

Correct. This has been verified by BTS in the past.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

...It becomes a question of weighing the benefit of reducing engaging tanks "to hit" chance versus increasing the probability of successful incoming shot hitting a weaker part of the tanks frontal aspect (the turret in the MkIV example).

That question is PRACTICABLY difficult to answer when you probably need it most...while playing a game!!

Its can be analysed, though, by a simple calculation if you have the data readily available, which it isn't.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

But, again, if memory serves the reduction in the "to hit" chance wasn't really focussed on. It came down to more of a discussion of the benefits of being hull down in the more abstract. Increased chance of retreating out of enemies LOS, being able to retreat and move about unobserved, and of course reducing the "to hit"

True, and as a rule of thumb, unless your tank has a significantly weaker turret and is at "close range" to an accurate firing gun(roughly speaking much less than 500m), the abstract reasoning will probably weigh in more heavily in favour of being hull down.

<BLOCKQUOTE>quote:<HR>Originally posted by Degrees of Frost:

- but by how much ? and is the reduction the same for all hull down AFV's ?

Again, it could be quantifiably analysed IF all the required data was given.

You would need this info for every situation that may be of interest to you in a CM game:

1) % chance to HIT turret/upper hull/lower hull/tracks in the both the "in open" AND "hull down" position at the range in question

2) % chance to KILL tank GIVEN a hit on the turret/upper hull/lower hull/tracks at that range

None of these factors are easily determined from CM, especially 2) as it involves complex penetration calculations with many variables. Both 1) and 2) could be determined empirically for very simple situations by doing CM "firing range" testing. Matching penetration values at range vs target armour/slope could be used as a very crude estimation for 2).

Lt Bull

Degrees of Frost · January 12, 2001

Thanks Bull ! The constant 37% decrease for all AFV's is interesting - one would think that it should probably vary somewhat from tank to tank given the variation in turret:hull size ratio's between different AFVs.

I for one would certainly be interested to see your graphs/tables/calculations and can only imagine others would as well. Maybe we could find some third party to host them for you .... anybody ?

That, of course, is assuming you would be comfortable with that Bull.

<BLOCKQUOTE>quote:<HR>Originally posted by Lt Bull:

quote: Originally posted by Degrees of Frost: "What does the reduction in size have on the "to hit" chance of engaging guns ?"

-------------------------------------------

I'm quite sure the modelling of hits vs guns is handle differently than hits vs vehicles as there appears to be no silhouette value for guns. Regardless, if you think about it, guns are in effect like a tank's turret, so they can be considered in some ways as a tank in constant "hull down" status (with only the turret exposed). Further, HE is primarily required to KO a gun, not AP.

Sorry I should have made that clearer - by "engaging guns" I meant the "to hit" chance of guns, either AT guns or mounted guns (TDs, tanks etc), firing at a hull down vehicle not the "to hit" for a tank firing at an AT gun.

So, in essence, just asking the same question "what effect does hull down status has on to hit chance ?"

<BLOCKQUOTE>quote:<HR>Originally posted by Lt Bull:

1) % chance to HIT turret/upper hull/lower hull/tracks in the both the "in open" AND "hull down" position at the range in question

2) % chance to KILL tank GIVEN a hit on the turret/upper hull/lower hull/tracks at that range

None of these factors are easily determined from CM, especially 2) as it involves complex penetration calculations with many variables. Both 1) and 2) could be determined empirically for very simple situations by doing CM "firing range" testing. Matching penetration values at range vs target armour/slope could be used as a very crude estimation for 2).

As to point one, my understanding CM calculates whether there is a hit or not and THEN determines where it will hit, the turret or the hull or the tracks or whatever.

When a hull down vehicle is "hit" I assume the same process is carried out but in this case CM determines whether it hits the upper hull or the turret. The impression that I have formed by reading various posts is that a "hit" is always a "hit", its just that possible hit locations are altered in relation to the tank-being-hit's aspect to the round that hit it. So once a hit is scored on a hull down vehicle it is going to remain a hit - the possible hit location calculation does NOT include the lower hull and tracks with "hits" to these locations being changed to misses.

Now those paragraphs is as clear as mud, sorry everyone its summer here in Sydney and I had a long swim this morning followed by a huge cooked breakfast and I am not sure my brain is working particularly well.

I am not particularly interested in the "to kill" chance - I am mainly interested in the to hit chance and how being hull down alters it. I recognise that range and gun type will have a big impact on these calculations

Thanks again Bull.

[This message has been edited by Degrees of Frost (edited 01-11-2001).]

Degrees of Frost · January 19, 2001

I was hoping that some other members of this forum might like to comment on the reduction "to hit" associated with targeting a hull down AFV versus targeting the same vehicle in the open.

Lt Bull has suggested that his/her (you never know) calculations suggest that the silhouette of ALL vehicles is reduced by 37%.

I do understand that hull down is abstracted in CM. A vehicle is hull down or it is not. But surely some vehicles are able to "shed" more or less silhouette when they are hull down.

Things like the Marder tank destroyers have a large and highset gunshield that one might expect to stand out like a sore thumb even when the vehicle is hull down. Should these vehicles "shed" the same amount of silhouette as a turreted tank (say a panther or a Mk IV) ?

And I still would love to know how silhouette effects "to hit" ?

Is it the most important factor after range for example ?

bredberg · January 19, 2001

I'll bet you that in CM2 (if and when they are done with it) the amount of silhouette will be computed, and hence the average of 37% (or what ever) will not be used.

(By the way I totally agree with you that this percentage would wary a lot between different AFVs - additionally all tank crews would not position their tank in the optimal hull-down position, and hence would show more than is necessary.)

It would be fairly easy to implement a hull-down computation since CM already includes a similar tool in the LOS.

You simply use the LOS from the gun and the compute which part of the target that can be seen and hit - maybe this is already included in CM.

Eagerly waiting for a moderator....

Cheers Jonas

Quenaelin · January 19, 2001

I thought this was realistically simulated, and shell actually flies throuh the air or isn't it so?. Becouse obviously it is harder to hit target if it is carefully covered (in rightly posted hull down position) and not just partially hull down. But if shell trajectory isn't simulated allready, then I think this should be modified to CM2. This kind of hit propability stuff is getting my nerves. How can you calculate in the heat of action how much whichever target is covered and which is propability to hit it. It should only be estimated value of hit propability not the real value. And shell should be simulated when it is going through air and trees and any obstacles it passes, not these cheap calculation stuff on hit propability. That is my opinion. If something should be changed to CM next version, this simulation thing is one thing and better graphics is second.

:USERNAME: · January 19, 2001

Vehicles should have gradients for this protective posture.

It should be:

1. Vehicle down

2. Commander up (or turret down)

3. Hull down (no bow mgs)

4. Track down (bow mgs up)

5. None

In my opinion a vehicle like the Panzer IV in a true HD situation is short changed. This tank (which until recently was over sized) has a very small turret in comparision to other vehicles. It should be reduced to about 1/3 its size in a hull down position.

CM makes it difficult to command your units into HD and somewhat under models its effects if your units get this status.

I havent played that much 1.1 but is the reciprocacy of HD still prevalent? I noticed that every time I was HD so was the target?

Lewis

Jeff Duquette · January 19, 2001

<BLOCKQUOTE>quote:<HR>Frost Said:

But, again, if memory serves the reduction in the "to hit" chance wasn't really focussed on. It came down to more of a discussion of the benefits of being hull down in the more abstract. Increased chance of retreating out of enemies LOS, being able to retreat and move about unobserved, and of course reducing the "to hit" - but by how much ? and is the reduction the same for all hull down AFV's ?<HR></BLOCKQUOTE>

Toward the tail end of the thread I posted a “to hit” based British Army Tests conducted during the war. Here it is again.

The percentage of a tanks silhouette that is covered as a result of being hull-down has several variables. The first of course is the vehicle geometry. The second is the relative elevation between target and firing tank. Third is the maximum depression or elevation possible within the gun tube of a tank.

Degrees of Frost · January 22, 2001

<BLOCKQUOTE>quote:<HR>Originally posted by Jeff Duquette:

Toward the tail end of the thread I posted a "to hit" based on British Army Tests conducted during the war.

Thanks for re-posting those graphs Jeff. Do you have any idea how reduction of size would alter these "to hit" curves (given that a Tiger turret is on the largish size ) ?

But is that pattern of decrease in the "to hit" chance plotted against range what we see in Combat Mission ?

It certainly backs up some individuals observations that getting your tank hull down against attacking enemy guns/tanks that have closed to shorter ranges (less than 500m) does not make you necessarily much harder to hit.

But we still don't know how "to hit" is calculated in Combat Mission.

How is silhouette "weighted" in these calculations ?

Does a 37% reduction in silhouette make a hull down tank significantly harder to hit at ranges under 500m ?

<BLOCKQUOTE>quote:<HR>Originally posted by Jeff Duquette:

The percentage of a tanks silhouette that is covered as a result of being hull-down has several variables. The first of course is the vehicle geometry. The second is the relative elevation between target and firing tank. Third is the maximum depression or elevation possible within the gun tube of a tank.

I think that most people would agree with you there Jeff. But in the wonderfully abstracted world of CM there is ONLY hull down or not down.

<BLOCKQUOTE>quote:<HR>Originally posted by USERNAME:

In my opinion a vehicle like the Panzer IV in a true HD situation is short changed. This tank (which

until recently was over sized) has a very small turret in comparision to other vehicles. It should be reduced to about 1/3 its size in a hull down position.

The data presented by Jeff (for the second time) would suggest that maybe at short ranges the Mk IV isn't being shortchanged but at long ranges perhaps it is ........ ?

On the otherhand maybe tank destoyers like the Nashhorn and Marder series aren't being penalised enough ..... not to mention Priests and Sextons.

Maybe I should run some tests of my own ...... might be a while though given I am having enough trouble keeping up with my PBEM demands.

What reduction in silhouette associated with going hull down ?

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