# RPG combat maths

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So I am thinking about how to implement the combat system in my RPG, thought I might run some ideas past the crowd to see if they are sensible / stupid. It's fairly basic at the moment, want to get it working before making it more complex!

(Oh, should mention: there is no hand-to-hand (or sword-to-hand) combat in my game, it's not about swords and dungeons, so basically just about everything can be classed as "magic")

I'd like to consider each "spell" - I call them "ability" - as being a synthesis of traits. A "trait" consists of a type of attack (might be "fire" or "electricity"), and a skill level at that. So for example a hand grenade might have the traits {physical,fire} and so the damage it inflicts will be a combination of the damage from the individual traits.

I intend to implement "luck" in a slightly different way from what seems to be standard. Basically I will consider luck to be 100%-skill. Luck will shift the computed damage around. At low luck levels (ie high skill levels) rather than having a symmetric normal distribution (or far worse, uniform), the distribution will be skewed so that a boost of some percentage is much more likely than a cut. At low skill levels, the skew in the distribution flips - you are more likely to reduce the computed damage. At 50% luck, the distribution is effectively normal and symmetric.

Doing damage (or healing, or winning a battle, or...) gains players experience points, and those EXP eventually yield players tokens to upgrade their skill level in particular traits ("Child of Light" style in a graph). Each player in the team has a slightly different multiplier for exactly how much their skill increases when they buy a token for it (the trait "affinity") as well as a personal maximum for that trait. So although each player can develop any skill, it will pay to consider their skills.

Big question I'm starting to ponder: given a set of mechanics, how does one determine the order of upgrade nodes in the development graph(s)?

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>> how does one determine the order of upgrade nodes in the development graph(s)?

are you referring to the unreal engine?

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>> how does one determine the order of upgrade nodes in the development graph(s)?

are you referring to the unreal engine?

Oh no, I mean that there's a graph of nodes that a player traverses (see Child of Light / Final Fantasy X), whereby each time you hit a node you are conferred some upgrade to your stats or skills. In the Child of Light system you are granted tokens, you can move a node on for every token you obtain.

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To know what path your players should take, I think, you need to have an idea of the destination. Do you have a final battle of some sort in mind? Do you have an idea of how powerful or what abilities you want your players to have when they reach the end? Will there be a few key abilities or items that the players will need to be able to finish the game?

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How much choice do you want the player to have?  In some systems a node does only one exact thing, but in other systems a node gives a player a choice between 2 or 3 options.  Also have you made a list of all your options yet?  It's important to know things like whether the player can separately increase their resistance to or affinity for each particular elements.  No point having physical damage resistance if nothing deals physical damage, but what about resistance to status ailments?  Is HP something that's increased through this upgrade grid or does it increase in some separate way?  And how does MP work, is there one MP gauge that is spent for all types of magic, or something like FF8 where there are separate reservoirs of each element of magic?

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Lots to think about! Thanks for the help so far. This is clearly going to take some iteration to get right. My instinct is to get a "simple" system going and see how it works in practice.

One of my ideas for the game is to have a single common "MP" bar for all the goodies. This will take the place of both MP and to some extent money, and will add an element of resource management.

I am now very much leaning towards a "Child of Light" style upgrade system where battles earn you exp, exp levels you up, levelling up yields a number of tokens that moves you along a path in the Tech Graph. Most basic nodes allow a +1 trait increase, but I am thinking that I might make the Tech Graph a sub-game in itself - think Monopoly but with tokens up for grabs.

Thoughts?

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>> Big question I'm starting to ponder: given a set of mechanics, how does one determine the order of upgrade nodes in the development graph(s)?

IE the order of perks in a perk tree:

in order form least to most useful. how else would you do it?

unless i misunderstand the question...

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As you describe it, "luck" consists of doing more damage with any attack: it is very incoherent with having separate skills for different attack traits.

In some games, particularly tabletop roleplaying games relying on other types of character building and advancement, there is no place for skills or other stats attached to specific attack "traits"; what attacks are possible and their damage could be collapsed to two trait-oblivious skills or stats (e.g. "magical power" and "magical lore") or one (e.g. "magical aptitude"), or even to no skill at all (all characters are equally good at spellcasting).

"Luck" at dealing damage in general, if present as a stat or skill, would be opposed to something completely different, e.g. "luck" at obtaining good answers from divination magic or contact with the gods or "luck" in interactions to lead and persuade other people.

On the other hand, in a complex, combat-oriented CRPG most players would expect the harmonization to go the opposite way: skill at dealing damage should be specific to some subsets of attacks, in the same way as skill at pulling them off.

For example, "fire attack damage" paired with "maximum fire spell level" and/or "fire spell failure probability by spell level" (or individual spells bought as separate skills, if appropriate).

With the choice between improving "luck" and improving spell sophistication there would be a natural way, on top of the specialization towards different magical traits, to distinguish between a character build that can do something nasty but only at low power and a character build that can hit hard but only in simple ways, with the obvious convergence path of doing a lot of damage with complex attacks.

Bonuses to all damage should be reserved for buffing effects, including magical items.

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