gacha
v0.2.1
Published
Roguelike item drop distribution calculator
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Maintainers
Readme
Node Gacha
Node Gacha (named after the Japanese onomatopoeia for the sound made by toy machines) aims to be a module providing different methods for calculating randomness in games. Randomness can include everything from enemy encounters to item drop rates, particularly useful for RPG's and Roguelikes.
Eventually we'll offer a few different systems, but for now we only support "roguelike".
npm install gacha
Roguelike
Purpose: Given a listing of items (or enemies) with variable drop rates, determine the odds of them being dropped on a particular level.
Diagram
The above diagram gives a visualization of how Roguelike works. Each item has an ideal level (center of curve), a spread (the radius of the curve), and a weight (makes it taller). After passing data through the roguelike function, a list of probabilities of each item spawning is provided on a per-level basis.
Code Sample
var gacha = require('gacha');
// items must be an object where each property contains level, weight, and spread.
var items = {
"101": {
"name": "Knife",
"type": "weapon",
"level": 1,
"weight": 1.0,
"spread": 1
},
"102": {
"name": "Sword",
"type": "weapon",
"level": 2,
"weight": 1.0,
"spread": 2
},
"103": {
"name": "Iron Buckler",
"type": "shield",
"level": 3,
"weight": 3.0,
"spread": 3
},
"104": {
"name": "Potion",
"type": "heal",
"level": 3,
"weight": 1.0,
"spread": 2
}
};
var equip = gacha.roguelike(items, function(item) {
// Optional filter callback, defaults to `return true;`
return item.type !== 'heal';
});
console.log(equip); // Shown below
// Which item should we spawn on level 3?
var lvl3 = equip[3];
var strata = Math.random() * lvl3.total;
var item = null;
for (var i = 0; i < lvl3.strata.length; i++) {
if (strata <= lvl3.strata[i]) {
var id = lvl3.lookup[i];
item = items[id];
break;
}
}
console.log("Receiving item for level three:", item);
Resulting equip
object
{
"0": {
"lookup": [ "101", "102", "103" ],
"strata": [ 0.24197072451914337, 0.3457475988742921, 0.4485344854101383 ],
"total": 0.4485344854101383
},
"1": {
"lookup": [ "101", "102", "103" ],
"strata": [ 0.3989422804014327, 0.6186379251352939, 0.8551480729542124 ],
"total": 0.8551480729542124
},
"2": {
"lookup": [ "101", "102", "103" ],
"strata": [ 0.24197072451914337, 0.5240655162930214, 0.9140048277385038 ],
"total": 0.9140048277385038
},
"3": {
"lookup": [ "102", "103" ],
"strata": [ 0.2196956447338612, 0.6803545106956419 ],
"total": 0.6803545106956419
},
"4": {
"lookup": [ "102", "103" ],
"strata": [ 0.10377687435514871, 0.493716185800631 ],
"total": 0.493716185800631
},
"5": {
"lookup": [ "103" ],
"strata": [ 0.2365101478189184 ],
"total": 0.2365101478189184
},
"6": {
"lookup": [ "103" ],
"strata": [ 0.1027868865358462 ],
"total": 0.1027868865358462
}
}