Since I haven't yet finished editing my BACC rules for New Edenia, I thought I ought to post what I have started working out: how I somewhat-randomly determine if sims will get a divorce, and whether or not I will ignore their wants, or lack thereof, to get engaged or married.
Relationship Satisfaction Calculation
I set this little math simulation up to avoid determining my sim’s romances by pure aspiration or personality calculations, because basing things in aspiration or zodiac gets extremely boring for me, and it’s why I have hacks to make all lifetime wants accessible to all sims and am not above randomly reassigning One True Hobbies.
For each sim in my neighborhood I use a four sided dice to create the following statistics:
Preferred Minimum Level of Attraction (dice -1 = bolts)
Preferred Minimum Shared Interests
Preferred Maximum IDF difference
Sims with a marriage priority of 1 will not propose engagement, but may accept it. I have some sims that I use a marriage priority of zero with, indicating that they actively do not want to be married, but since this precludes actually getting married, and most of these sims will avoid going steady, I generally do not calculate relationship scores for these sims.
Shared interests are considered to be interests that both sims have 7+ points in, essentially their most frequent topics of conversation.
Each sim also has a randomized Ideal Family Size, which I set in ACR, but also record for the purposes of this calculation and determining if a sim will adopt or reproduce via plantsimism or alien abduction.
Calculating Relationship Satisfaction
When sims enter a committed relationship (going steady, engagement, marriage) I calculate their relationship satisfaction scores. This tells me how likely sims are to break up after a “honeymoon period” of one season from each relationship upgrade, and how likely they are to argue.
1) The relationship’s positive points overall is calculated by the following: Bolts + Shared Interests + IDF difference modifier.
a. IDF difference modifier: 0 = +2 points, 1,2 = +1 point, 3,4 = +0 points, 5,6 = -1 point, 7, 8 = -2 points. (Generally I do not use an IDF of higher than seven or eight.)
b. The IDF difference is calculated based on the difference between number of additional children desired (IDF – current offspring) between the two sims. Therefore a sim with an IDF of 10 who has had 4 children from previous partners is perfectly matched in this regard with a sim who has an IDF of 6 and no offspring. A sim with an IDF of 3 who has 2 children from a previous relationship is poorly matched in this regard with a childless sim who has an IDF of 6 and no children.
2) Each sim’s dissatisfaction points (up to three) are then calculated separately.
a. Actual bolts – preferred minimum attraction = if this number is negative the sim gains one dissatisfaction point.
b. Actual shared interests – preferred minimum shared interests = if this number is negative the sim gains one dissatisfaction point.
c. Maximum desired IDF difference – actual IDF difference = if this number is negative the sim gains one dissatisfaction point.
3) The overall relationship score is the positive points minus the total number of dissatisfaction points. This score rules whether sims will propose, and how likely sims are to break up after their “honeymoon period.”
Proposal and acceptance odds are calculated using a sim’s marriage priority plus their relationship score. This total must be above zero to propose, and at or above zero to accept. At least one sim in the pair must also roll a marriage or engagement want to propose.
If a sim proposes to a sim whose odds are below zero, I roll a 4 sider to determine how many days they have to raise the score before the sim with the negative odds breaks the engagement.
A sim with a special marriage priority of zero will break the engagement within 1 d4 days (I roll this randomly.) I usually only assign this to sims who are either afraid of commitment according to the extra personality traits I assign in their bios, or aromantic and don't want a marriage, maybe just a live-in best friend. (Though if I have ACR set right, I won't get sims in a position to propose to aromantic sims.) See this post for how I manage to play asexual and aromantic sims despite having ACR pretty much running itself.
The period during which sims will not automatically argue if they have low relationship satisfaction, set as 1 season after latest relationship upgrade. (Relationship upgrades include “going steady” getting engaged, moving in together, and getting married.) It only includes days on their home lot, not days spent on vacation / running businesses, etc.
Dissatisfaction: After the honeymoon period, roll a 6-sider versus each sim’s dissatisfaction points each day to determine whether or not they will initiate one argument. Sims with higher dissatisfaction scores are therefore more likely to argue, and there is a maximum 50% chance that they will argue each day due to dissatisfaction.
Stress Arguments: When a sim makes a bad (red) memory or goes into red aspiration, they will argue with their partner once for each dissatisfaction point. For example, if a house is robbed, triggering a couple with 2 dissatisfaction points each to argue, each sim will initiate an argument “about the robbery” twice.
Kids: a sim who has zero more desired children will automatically argue with a partner who wants more after each child birthday or their partner rolls a want to have a baby.
Sims who fall out of love may divorce or break up at any time. Sims who lose their friendship will separate automatically.
A sim’s marriage priority determines how many days they will wait to repair a relationship before divorce after a partner cheats. Sims with a marriage priority of 1 have 2 days to repair the relationship or go to counseling, sims with a marriage priority of 4 have five days. I use each sim’s ACR jealousy settings to determine if they actually should have jealousy, and will cheat to remove furiousness from non-jealous sims who “caught a partner cheating.”
Each sim with more than one dissatisfaction point has a likelihood of divorce from sheer dissatisfaction after the honeymoon period, which is calculated by Relationship Score + Marriage Priority – dissatisfaction points. If this score is below 0 for Marriage Priority x 3 days, sims will roll a six sider versus their dissatisfaction points minus 1 every day to break up. The maximum is a 33% chance per day of divorce. I don't start rolling for this until 1 day after the couple has first had a mandatory argument.
Improving Relationship Score:
1) The easiest method would be to change turn ons/offs via a matchmaker potion or the Re-nu-yu orb, but those don’t account for very much of a relationship score. (Additionally, some attractances can be improved by improving skill sets.)
2) - Use magazines to improve the number of shared interests. It helps to find interests that only barely don’t count as major interests.
3) - Sims who learn parenting have their acceptable difference in ideal number of children bumped up by one.
4) - IDF differences can improve if a sim has had offspring elsewhere, also difficult pregnancies can bring IDF’s over 5 down a point or two. Sims who have excessively difficult pregnancies or who roll fears of having babies can have their IDF reduced.
5) - Sims who learn couples counseling get a -1 to the number of arguments rolled for.- Sims who learn lifelong happiness have their dissatisfaction score reduced by one.
Denise and Jasen are married and have a relationship score of -1. Denise’s marriage priority is 2 and dissatisfaction is 3, whereas Jasen’s MP is 1 and dissatisfaction is 1. Denise has a 2/6 chance of divorcing Jasen after 7 days of marriage (because even though 3 x a marriage priority of 2 means she could start on day 6, that's also the first day they'll have to roll for arguments,) a 3/6 chance of initiating a random argument, and will argue with Jasen three times for every red memory she makes. Due to only having one dissatisfaction point, Jasen will not automatically roll to divorce Denise under any circumstances, but will have to roll for arguments starting on day 6 of marriage, argue once per red memory.
Casilda and Toby are going steady and have a relationship score of -3. Casilda’s marriage priority is 4 and dissatisfaction is 2. Toby’s marriage priority is 3 and dissatisfaction is 2. Toby cannot propose to Casilda, but Casilda can propose to Toby and he will accept.
After marriage, Casilda will have a 1/6 chance of divorcing Toby after 12 days of marriage. After the honeymoon period she will have a 2/6 chance of initiating a random argument, and argue with Toby twice for each red memory. Toby will have a 1/6 chance of divorcing Casilda after 9 days, a 2/6 chance of a random argument, and argue twice for each red memory.
Ashleigh and Gibson are going steady and have a relationship score of 7. Both have a marriage priority of 2 and no dissatisfaction points. Either one can propose and/or accept a proposal.
If married or cohabitating, neither will have to roll for random or stress arguments, but arguments can still be triggered by differences in their IDF. In my game, these two randomized with zero jealousy, so they shouldn’t be broken up by cheating either.
Sura Kyo and Tesla Krakow are married and have a relationship score of zero. Sura has an MP of one and a dissatisfaction of 2. Tesla has an MP of two and a dissatisfaction of 2. Sura would start to roll for arguments and divorce on day 3, except that’s part of the honeymoon period so she has to wait for day 6. After day 6, Sura has a 1/6 chance of divorce, 2/6 chance of argument. Tesla will have the same chances on day 6. Both will argue twice for each red memory.
Sura’s Ideal Family Size is zero, and Tesla’s is seven, so when she and Tesla have a kid they will immediately start arguing over having more at every birth and birthday related to that child. For every child that exceeds Sura’s IDF, a point will be added to their IDF difference modifier, so that it will go up first to 8, then to 9, (at which point it will drive their relationship score to negative 1).
I've seen a lot of people try to randomize other things, but never this, so I thought I'd give it a go, and put it up here so that people who aren't math-averse can do it too. If you don't have a 4 sider, I recommend using a regular 6 sided dice and just re-rolling if you get 5 or 6. Or you can use random.org, or any dice rolling program.