RenderTexturePool

RenderTexturePool.cs

// Sometimes, RenderTexture.GetTemporary() and RenderTexture.ReleaseTemporary() leak textures.
// For those times, there is RenderTexturePool.

using System.Collections.Generic;
using Unity.Collections;
using UnityEngine;

public class RenderTexturePool {
    readonly Dictionary<RenderTextureDescriptor, List<RenderTextureCounter>> _pool;
    readonly int _initialListCapacity;
    readonly int _expireAfterFrames;

    public int PooledCount => _pooledCount;
    int _pooledCount;
    public RenderTexturePool(int initialDictCapacity, int initialListCapacity, int expireAfterFrames = 5) {
        _initialListCapacity = initialListCapacity;
        _pool = new Dictionary<RenderTextureDescriptor, List<RenderTextureCounter>>(initialDictCapacity);
        _expireAfterFrames = expireAfterFrames;
    }
    public RenderTexture GetTemporary(RenderTextureDescriptor desc) {
        RenderTexture rt;
        if (_pool.TryGetValue(desc, out var list)) {
            if (list.Count > 0) {
                rt = list[0].rt;
                list.RemoveAtSwapBack(0);
                _pooledCount--;
            }
        }
        rt = new RenderTexture(desc);
        return rt;
    }

    public void ReleaseTemporary(RenderTexture renderTexture) {
        var rtCounter = new RenderTextureCounter { rt = renderTexture };
        if (_pool.TryGetValue(renderTexture.descriptor, out var list)) {
            list.Add(rtCounter);
            return;
        }
        list = new List<RenderTextureCounter>(_initialListCapacity) { rtCounter };
        _pool.Add(renderTexture.descriptor, list);
        _pooledCount++;
    }

    public void UpdateFrameCounts() {
        foreach (var list in _pool.Values) {
            for (int i = 0; i < list.Count; i++) {
                var rtCounter = list[i];
                if (rtCounter.unusedFrameCount > _expireAfterFrames) {
                    rtCounter.rt.Release();
                    list.RemoveAtSwapBack(i);
                    i--;
                    continue;
                }
                rtCounter.unusedFrameCount++;
                list[i] = rtCounter;
            }
        }
    }
    
    struct RenderTextureCounter {
        public RenderTexture rt;
        public int unusedFrameCount;
    }
}