public unsafe struct TriangleArray : IDisposable
    {
        private int _capacity;

        private int _length;
        public int Length => _length;

        private Triangle* _array;

        public Triangle* this[int index]
        {
            get
            {
                return &_array[index];
            }
            set
            {
                _array[index] = *value;
            }
        }

        public TriangleArray(int capacity)
        {
            _array = (Triangle*) Marshal.AllocHGlobal(capacity * sizeof(Triangle)).ToPointer();
            _capacity = capacity;
            _length = 0;
        }

        public void Clear()
        {
            _length = 0;
        }

        public int AddExisting(Triangle item)
        {
            CheckCapacity();
            _array[_length++].CopyFrom(item); //in case GC kills above item
            return _length - 1;
        }

        public Triangle* GetNew()
        {
            CheckCapacity();
            return &_array[_length++];
        }

        public int RemoveAt(int index)
        {
            _array[index] = _array[_length - 1];
            _length--;
            return _length - 1;
        }

        public Triangle[] ToArray()
        {
            var array = new Triangle[_length];
            for (var i = 0; i < _length; i++)
            {
                array[i] = _array[i];
            }
            return array;
        }

        public void Resize(int newCapacity)
        {
            var arrayIntPtr = (IntPtr) _array;
            var newArrayPtr = Marshal.ReAllocHGlobal(arrayIntPtr, (IntPtr)(newCapacity * sizeof(Triangle))).ToPointer();
            Marshal.FreeHGlobal(arrayIntPtr);
            _array = (Triangle*) newArrayPtr;
            _capacity = newCapacity;
        }

        public void Dispose()
        {
            Marshal.FreeHGlobal((IntPtr)_array);
        }

        private void CheckCapacity()
        {
            if (_length >= _capacity - 1)
            {
                Resize(_capacity * 2);
            }
        }
    }