Stat Encapsulation

I forgot to charge my laptop yesterday so used the forced break to practice my sketching, but I’m back in it today and development continues.

The Mutation Map tool now has the ability to view and edit both the overall map and the individual stats of each head. It can also do the same for Feet, and I’m working on getting the remaining mutation maps (Limbs, Coverings, Colour Patterns, Feature Models and Feature Textures) into the tool. Hope to be done by the end of the week and moving on to other things, though that may be a bit optimistic.

Also took some time to begin taking my Stat encapsulation to the next level. Currently we have 6 types of Stat:

  • GeneticStats encapsulate a mutation rate, plus mutate, randomise and blank routines, for every gene.
    • FloatingGeneticStat: A hereditable decimal number, like “torsoWidth” or “headSize”. Encapsulates an upper limit and lower limit in addition to the mutation rate.
    • DiscreetGeneticStat: A hereditable integer number, like “numberOfFeatures”. Just encapsulates the mutation rate.
    • BooleanGeneticStat: A hereditable yes/no value, like “hasTail” or “hasNeck”. Just the mutation rate again.
    • MappedGeneticStat: A stat with a mutation map, like “headType” or “bodyCovering”. Encapsulates the entire mutation map structure.
    • BasalStat: a non-hereditable stat which is imported from an external file, linked to a MappedGeneticStat. Like how HeadType determines Diet, or how LimbTipType determines BaseLimbDamage. These stats are rarely used directly: usually, they feed into formulas to determine other stats. (diet is an exception)
    • UpdatableAttribute: a type of Stat I have encapsulated but haven’t derived from IStat yet: these are things like Health, Energy and Biomass, which change over the course of a creature’s life. Encapsulates a list of “Deltas”, making it possible to track the source of changes to these stats (you can see these deltas listed out on the energy page in creature details).

There’s only one major type of stat still missing, at least on a per-creature level:

  • DerivedStat: Any stat which calculates itself from other stats. For instance, Speed takes into account LimbSize, LimbBaseSpeed, TorsoWidth, TorsoRotation, LimbTipBaseSpeed, and so on. DerivedStat will encapsulate all these stats, plus the formula used to combine them.

The method I’m using to encapsulate the formula uses something I haven’t spent much time with in the past: delegates. I’m storing it the entire formula as a delegate inside the DerivedStat instance. This means I get to define the formula in StatData, but still use the built-in accessors of the objects, so I get the same intellisense benefits and high performance as if I was defining  the calculation over in Phenotype.

The result looks like this:

AddDerivedStatType(
    "mass",                                                          //Name
    "Mass",                                                          //Printable Name
    "Determines how much stuff there is in the thing",               //Printable Description
    delegate(Genome genome, BodyPlan bodyPlan, Phenotype phenotype)  //boring code stuff
    {
        return bodyplan.Volume * genome.Skin.Density;                //Formula
    }
);

The relevant bit is the second-last line: that’s the only place that formula needs to be defined. All I have to do later is call Initialise, and the DerivedStat takes care of calculating itself on behalf of it’s parent creature, pulling other stats in and combining them, as well as throwing errors if stats haven’t been correctly initialised.

Yes yes, making with the boring and the code and the words and the stuff, so what? Why do we care?

Here’s why we care: every calculation, limit and mutation rate from the raw genes to attributes like speed and stamina is now stored in StatData. This one file is becoming the spinal column of a lot of the simulation’s behaviour, so tweaking mutation rates, adding limits, changing names and descriptions, and now adjusting stat formula will all be possible simply by changing the input data here.

And I intend to expose that input data to modding.

Cue the maniacal laughter,

Qu

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