Set of utils for make work with random selections more comfortable.
Includes Randomizer and Weighted List.
https://assetstore.unity.com/packages/slug/169229
- Non-repetitions random.
- Flat-distributed random.
- Allow to set weights for list items, and then select randomly by weight.
- Inherins IList and IReadOnlyList interface - you can use it as usual List.
- Property drawer included to easy setup in inspector.
To use Randomizer, you need to create and store its instance:
_randomizer = new Randomizer(_prefabsList.Count);
It needs to be initialized with amount of items to select from. Randomizer designed to work with arrays and lists, so, its only returns inreger indexes, limited in range from 0 to initialized amount.
To get indexes without repetitions, use next:
int index = _randomizer.SelectNoRepeat();
To get indexes flat-distributed:
int index = _randomizer.SelectFlatDistributed();
Both functions returns integer number in range from 0 to amount value, which constructor was initialized with.
WeightedList<T> inherits standard C# interfaces IList<T> and IReadOnlyList<T>.
Internally, it consists form usual List<T>, and list of assotiated weights (List<float>).
So, you can use it in your code exactly like List<T>, except you have to add weights, when its necessary:
Constructor (also parameter-less constructor available):
WeightedList(List<T> objects, List<float> weights)
int IndexOf(float weight)- get first index of item with given weight.int IndexOf(T item)- get first index of item.void Insert(int index, T item)- inserts item at index with 0 weight.void Insert(int index, T item, float weight)- inserts item at index with given weight.void Add(T item, float weight)- adds item to the end of list with given weight.void Add(T item)- adds item to the end of list with 0 weight.
To keep usage safe, Weighted List implements read-only interface:
public interface IReadOnlyWeightedList<T>
{
T GetRandomByWeight();
float GetWeightAtIndex(int index);
float GetTotalWeight();
float GetNormalizedWeightAtIndex(int index);
}
Lets describe it:
T GetRandomByWeight()- itd a main routine to use: it randomly selects an item from list by its weight.float GetWeightAtIndex(int index)- allows you to know the weight at particular index.float GetTotalWeight()- returns the sum of all weights.float GetNormalizedWeightAtIndex(int index)- Normalized weights means the weight value, proportional to absolute value, but when the total weights sum equals 1. For example, we have two items, weigths are 2 and 6. Normalized weights for these items are 0.25 and 0.75.
Additionally, WeightedList<T> provides next methods:
void SetWeightAtIndex(int index, float weight)- sets weight for item with given index.void Normalize()- normalizes all weights (total weights sum will be 1).void SetWeightOf(T item, float weight)- sets weight for particular item (first occurance).
To make it comfortable to use Weighted List in unity, custom property drawer provided.
Usage:
- Inherit concrete implementation of generic WeightedList (dont forget the Serializable attribute):
[Serializable] public class WeightedListOfPrefabs : WeightedList<CustomPrefab> { }
- Inherit property drawer and mark it with attribute:
[CustomPropertyDrawer(typeof(WeightedListOfPrefabs))]
public class MyPropertyDrawer : WeightedListPropertyDrawer { }
Provided property drawer supports any basic type, and any type, inherited from UnityEngine.Object. Plain c# classes supported as read-only (but no limits to use plain classes in code).
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