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Hi there, my brethren-in-arms!
I spontaneously visited the Imperial Guard forum last night and came across a thread about drop troops. Since I myself am hardly ever concerned of the issue of scattering (drop pods are pretty safe to land close to the enemy, my terminators usually come in in the vincinity of veterans with teleport homers) I have never before cared much to translate the risks into seizable numbers.
Last night, though, I juggled some probabilities and did some calculations. And since today I was confronted with the problem of estimating the risk of scattering fatally upon deep-striking to a specfic position here I thought it would not hurt to share my results.
Scattering has two components: distance and direction. For our purposes we will measure range in inches (who could have guessed) and direction in degrees. While the latter is indicated completely by the scatter die the first is determined by both the distance dice and the scatter die (which can turn up with a "hit"). Do not be bothered with that too much yet, though.
Our scatter distance is 0" and 2-12" in increments of 1" each. Note that it is impossible to scatter 1". The following list provides percent chances of scattering the given number of inches or less.
0" (or less): 33.3%
2" (or less): 35.2%
3" (or less): 38.9%
4" (or less): 44.4%
5" (or less): 51.9%
6" (or less): 61.1%
7" (or less): 72.2%
8" (or less): 81.5%
9" (or less): 88.9%
10" (or less): 94.5%
11" (or less): 98.2%
12" (or less): 100.0%
This is pretty much it.
Now we need to work in the direction. Following the assumption that it is equally probable to scatter in any one direction we can calculate the risk of scattering into certain unopportune locations (enemy units, friendly units, impassable terrain) by dividing all possible directions (360°) by the arcs that pose a threat.
This may sound complicated and can indeed be in some situations. Let me elaborate these theoretical considerations in an easy example as to show how the given ideas are supposed to be used.
A unit of terminators is to deep-strike near a squad of Necron warriors. As the terminators will want to be sure to be able to assault the enemy in the turn following its arrival it is supposed to land within 6" of its target, that then could not foot-slog out of the 12" effective assault range of the terminators. But more important than deep-striking this close is the safety of the terminators who should hit secure ground (and not be destroyed due to bad scatter) with a probability of about 80%. The terrain is free of other units or impassable terrain.
When the terminators are placed in front of the squad of Necron warriors the latter will probably occupy an approximate 120° arc of the terminators' surroundings. Since 120° is a third of 360° the danger of scattering into the Necrons at any given distance can be divided by three. If you are willing to run a risk of 20% (100% - 80% safety) of your terminators scattering into the Necron warriors you can thus take a 60% (3 x 20%) of scattering too far because only a third of all directions are positively dangerous. Thus you would deep-strike your terminators 4" from the Necron warriors, the probability of scattering a maximum of 3" being 38.9%, the risk of scattering further (and eventually coming within 1" of enemy models thus being destroyed) therefore being 61.1% (100% - 38.9%), in the direction of the warriors only about 20% (a third of it). [Of course this is a little approximated since if you don't scatter directly towards the warriors but a little diagonally to them you could probably even scatter 4" without being harmed.]
Trying to deep-strike 4" in front of the enemy then still leaves you with an approximate 40%+ chance of effectively landing within 6" of the enemy squad (2" or less scatter away from the enemy squad with a probability of 35%/3 being negligible, 3" or less scatter towards the enemy squad with a probability of 39%/3 not being a problem either, and a scatter of 4" or less parallel to the enemy squad with a probability of 45%/3 being tolerable too, for a total of tightly calculated 40%).
Of course those calculations remain rules of thumb due to the arcs in our calculations remaining rather large increments instead of infinitely small ones like in an integral. Still these numbers and considerations are perhaps inspiration or orientation guide enough to prove useful to some player intending to deep-strike his troops with a rather carefully calculated (in comparison to purely intuitive estimation) amount of risk.
But regardless of this hopefully useful breakdown it is of course completely up to you to decide where you draw the line! Your style of play determines just how much risk you are willing to take in order to gain certain advantegous positions...
Enjoy the game and good luck with your scatter dice!
P.S.: sorry if things are difficult to understand. I am still having problems expressing myself on complex matters in this language.
that just made me feel dumb
haha, that was far too complicated for me to understand :p but intead of complaining i will congratulate you on your calculations
i hope 1 day, i too will have a spacemarine brain and be able to calculate on a similar level
In the name of the Emperor and for the Glory of the Imperium... Gimme Back My Girlfriend! :(
well I am not coming from the exact same angle as you all, actually probably the opposite. As a Tyranid player, if I don't deepstrike my Lictors within 6" they are basically lost.
Deepstriking always seems risky too me, but with marines since you don't always have to land within 6" that doesn't seem as bad. If your terminators don't reach you still have stormbolters and a +2 armour save to bail you out for an additional turn, right? I also think leaving a squad off table for a turn can help your opponent forget about them and allow them to sway the game when they come in.
As someone who loves Lictors I think I have to ignore the numbers because far too many times have I striked within 3" of an enemy and rolled a bulleye destorying nealy an entire havoc squad in one turn.
Very informative. I still find deep striking to be too risky, but calculating the scatter odds makes it seem more reasonable. The real problem is when they get shot up next round.
well this is nice, but since you declared that the percentages are (X" or less) it can be quite misleading. For example there are 6 sides to the scatter die. and there are 2 hit sides. so you will scatter 2/3s of the time or 66%. when you do scatter the chance to scatter 2" is the same for every other possiblity... (9%).. at least i think it is. .. anyway... cool post regardless
So, yes. There is a 33.3% chance of not scattering (i.e. scattering 0", as listed above) and a 66.7% chance of scattering something around 2-12". When listing the probability of scattering x" or less I have always included the chance of not scattering at all.
Now, if we scatter we do not, as you say (hope I am not getting you wrong on this) have the same chance for scattering 2" as we do for scattering 5". Because with 2d6 there is only one possibility to roll a 2 (1,1), but there are 4 posibilities to roll a 5 (4,1; 3,2; 2,3; 1,4). So the chance of scattering exactly 2" is 1/36 (1 out of 36 possible combinations that can be rolled with 2d6) of the chance of scattering at all (66.7%), equaling a chance of 1.9%.
That means that the chance of not scattering or scattering exactly 2" would be 33.3% + 1.9% resulting in 35.2% as given above.
Ecellent thread. First time I've ever seen it worked out before.
Keeper of the Dark Fortress
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Found this very useful, thanks!
"In dedicato imperatum ultra articulo mortis"
My can't brain today, I have the dumb.
Because my post seems a little difficult to understand I will write up a tutorial on how to calculate the risk this weekend, along with a "plan your own deep-strike"-kit featuring all the numbers you need in handy tables so you can just more or less "look it up" without doing much calculating yourself. I will add some more examples there and visualize them with some battlefield pictures. Any maybe even add some considerations on what to deep-strike when and where (at least for us space marines). Hope I can spare the time for that project! Look forward to it.