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--- dom6:drn [2024/06/04 18:00]
fenrir created
+++ dom6:drn [2026/06/22 05:27] (current)
wigglefig Copied information from the dom5 version because this one wasn't complete
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 ====== Dominions Random Number (DRN) ======
-Most skill checks use a **Dominions Random Number**, or a DRN. This includes virtually all Damage rolls, [[attack skill|Attack]] rolls, [[Precision|Missile Hit]] rolls, and so on.
+Most Dominions game mechanisms use something called the **Dominions Random Number (DRN**). This includes virtually all Damage rolls, [[attack skill|Attack]] rolls, [[Precision|Missile Hit]] rolls, and so on. When a random number is called for, the number used is usually actually a DRN. This is a roll of two six-sided dice (2d6) but with an additional bonus: if any individual die roll is “6,” one is subtracted, and then that die is re-rolled and added to the result. This is referred to as an “open-ended” 2d6 roll. The DRN is two six-sided dice. A lower-case "drn" is one six-sided die.
-The DRN is two six-sided dice. A lower-case "drn" is one six-sided die. Any dice roll described as an "XdY" (i.e. 1d4) without saying it's open-ended is closed.
+Example: The game calls for a DRN. Two dice are rolled and they come up 2,6. Because one of the
+dice was a “6,” one is subtracted from the total (making 7), and the die is rolled again. But this die is
+also a 6. So one is subtracted from the total (now up to 12) and a die is rolled again. It is a 4. The final
+result for this DRN is 16.
-What makes this different from regular six-sided dice rolls? Well, Dominions Random Number dice **explode**; if you roll a **6**, you make it a **5**, and then you **roll that die again**. The extra roll is added to your total. You continue to roll until you stop rolling 6's. This is called an "open-ended" roll in-game, while regular rolls are known as "not open-ended" or "closed".
+Note that if both original dice came up as 6, both would be re-rolled and added as above. If a die keeps coming up 6, it keeps getting re-rolled and added, which can very occasionally lead to large numbers. Dominions has a lot of situations where something is very unlikely to happen, like a militia soldier hitting an ethereal monster. However, in the real world of Dominions, very few things are actually impossible. To model this fact as closely as can be, the Dominions Random Number was created. With it, it is always possible for such an event to occur, which would not be the case if the roll was not openended. In some very few cases, there may be only one six-sided die rolled. It is still open-ended, but in this case, the rules refer to it as a drn, in lower-case letters. An example is the dispelling of global enchantments.
-==== Understanding the DRN ====
+====== Probabilities in Dominions 6 ======
+Most die rolls in Dominions 6 involve one player rolling higher than another player using the DRN system. To give players some idea of how likely something is to happen, here is a table that shows the difference between two values on the left, and the chance of beating that value using two open-ended dice on the right.
+<WRAP group>
+<WRAP column quarter>
+^ Difference ^ Chance ^
+| -30 | 0.006% |
+| -29 | 0.008% |
+| -28 | 0.012% |
+| -27 | 0.017% |
+| -26 | 0.023% |
+| -25 | 0.031% |
+| -24 | 0.043% |
+| -23 | 0.060% |
+| -22 | 0.082% |
+| -21 | 0.11% |
+| -20 | 0.16% |
+| -19 | 0.22% |
+| -18 | 0.30% |
+| -17 | 0.41% |
+| -16 | 0.55% |
+| -15 | 0.76% |
+| -14 | 1.0% |
+| -13 | 1.4% |
+| -12 | 1.9% |
+| -11 | 2.6% |
+</WRAP>
+<WRAP column quarter>
+^ Difference ^ Chance ^
+| -10 | 3.4% |
+| -9 | 4.6% |
+| -8 | 6.2% |
+| -7 | 8.2% |
+| -6 | 11% |
+| -5 | 14% |
+| -4 | 18% |
+| -3 | 24% |
+| -2 | 30% |
+| -1 | 38% |
+| **0** | **46%** |
+| 1 | 54% |
+| 2 | 62% |
+| 3 | 70% |
+| 4 | 76% |
+| 5 | 82% |
+| 6 | 86% |
+| 7 | 89% |
+| 8 | 92% |
+| 9 | 94% |
+</WRAP>
+<WRAP column quarter>
+^ Difference ^ Chance ^
+| 10 | 95% |
+| 11 | 97% |
+| 12 | 97% |
+| 13 | 98% |
+| 14 | 98.6% |
+| 15 | 99.0% |
+| 16 | 99.2% |
+| 17 | 99.4% |
+| 18 | 99.6% |
+| 19 | 99.7% |
+| 20 | 99.79% |
+| 21 | 99.84% |
+| 22 | 99.89% |
+| 23 | 99.92% |
+| 24 | 99.94% |
+| 25 | 99.96% |
+| 26 | 99.97% |
+| 27 | 99.978% |
+| 28 | 99.988% |
+| 29 | 99.991% |
+</WRAP>
+</WRAP>
+What does this mean? It means that if you have a Jotun Moose Rider with attack skill 9 and your opponent has an Abysian Infantry with defense skill 10, your chance of beating him with two open-ended dice (and thus scoring a hit) is 38%. If the values were reversed, your chance of success would be 54%. Why the seeming disjunction? Because the “zero-point” is only 46%. Remember – the table shows the chance of beating your opponent. Thus, if you are evenly matched, you need to roll higher than he or she does on the same type of dice, and thus your chances of doing so are less than even. 46%, to be exact.
+Sometimes the manual will state that a given effect requires a morale check (or some other ability check) “against” some number. This is simply a way of saying that a unit’s morale (or other ability) + DRN is compared to the stated number + DRN. So if a unit has to “take a morale check against 12,” this means the unit’s morale + a DRN is compared to 12 + DRN. If the unit has a morale of 10, the chart above would indicate that the chance of this unit passing the check is 30%.
+===== Rolls for success =====
+A common situation you'll find yourself in is trying to win one at least one of a series of particularly difficult rolls, such as trying to get a [[Soul Slay]] cast through the [[Magic Resistance]] of a [[super combatant]]. Here are a few values to orientate yourself around what to expect:
+^ Difference  ^ Single roll success  ^ Expected rolls for success (1 in ...)  ^ Rolls needed for >80% chance of one success  ^ Examples for magic pen against [[Magic Resistance]] of 18             ^
+| 0           | 46%                  | 2                                      | 3                                            |                                                   |
+| -1          | 38%                  | 3                                      | 4                                            |                                                   |
+| -2          | 30%                  | 3                                      | 5                                            |                                                   |
+| -3          | 24%                  | 4                                      | 6                                            | Hard to resist magic pen roll                     |
+| -4          | 18%                  | 6                                      | 9                                            |                                                   |
+| -5          | 14%                  | 7                                      | 11                                           |                                                   |
+| -6          | 11%                  | 9                                      | 14                                           |                                                   |
+| -7          | 8.20%                | 12                                     | 19                                           | Standard magic pen roll                           |
+| -8          | 6.20%                | 16                                     | 26                                           |                                                   |
+| -9          | 4.60%                | 22                                     | 35                                           |                                                   |
+| -10         | 3.40%                | 29                                     | 47                                           |                                                   |
+| -11         | 2.60%                | 38                                     | 62                                           | Easily negated magic pen roll                     |
+| -12         | 1.90%                | 53                                     | 84                                           |                                                   |
+| -13         | 1.40%                | 71                                     | 115                                          |                                                   |
+| -14         | 1.00%                | 100                                    | 161                                          |                                                   |
+| -15         | 0.76%                | 132                                    | 211                                          | Easily negated + ??Antimagic?? source  |
+| -16         | 0.55%                | 182                                    | 292                                          |                                                   |
+| -17         | 0.41%                | 244                                    | 392                                          |                                                   |
+| -18         | 0.30%                | 333                                    | 536                                          |                                                   |
+| -19         | 0.22%                | 455                                    | 731                                          |                                                   |
+| -20         | 0.16%                | 625                                    | 1006                                         |                                                   |
+| -21         | 0.11%                | 909                                    | 1463                                         |                                                   |
+| -22         | 0.08%                | 1220                                   | 1962                                         |                                                   |
+| -23         | 0.06%                | 1667                                   | 2682                                         |                                                   |
+| -24         | 0.04%                | 2326                                   | 3743                                         |                                                   |
+| -25         | 0.03%                | 3226                                   | 5191                                         |                                                   |
+| -26         | 0.02%                | 4348                                   | 6997                                         |                                                   |
+===== Understanding the DRN =====
 Due to how the DRN works, there are few skill checks that are utter guarantees, and determining what the result of a roll will be is even more difficult.
-=== drn Math (One Die) ===
+==== drn Math (One Die) ====
 You could zoom in on the odds of an open-ended six-sided die's results an infinite number of times, but let's just say you only expand twice at most:
@@ Line 51: / Line 167: @@
 </WRAP>
-=== DRN Math (Two Dice) ===
+==== DRN Math (Two Dice) ====
 <WRAP group>

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