using UnityEngine;

namespace Crest.Examples
{
    /// <summary>
    /// Simple script to play / stop any child particle systems based on viewer distance from this GO.
    /// </summary>
    public class ParticleSystemDistanceCulling : MonoBehaviour
    {
        public Transform _viewpoint;
        public float _maxDistance = 50.0f;

        bool _emitting = true;

        ParticleSystem[] _particleSystems;

        private void Start()
        {
            _particleSystems = GetComponentsInChildren<ParticleSystem>();
        }

        void Update()
        {
            var dist2 = (_viewpoint.transform.position - transform.position).sqrMagnitude;
            var maxDist2 = _maxDistance * _maxDistance;

            if (_emitting && dist2 > maxDist2)
            {
                _emitting = false;

                foreach (var system in _particleSystems)
                {
                    system.Stop();
                }
            }
            else if (!_emitting && dist2 < maxDist2)
            {
                _emitting = true;

                foreach (var system in _particleSystems)
                {
                    system.Play();
                }
            }
        }
    }
}