Raycast rain particle system

Rain.cs

using UnityEngine;
using System.Collections;

public class Rain : MonoBehaviour
{
    [SerializeField] protected ParticleEmitter m_ParticleEmitter;
    [SerializeField] protected Splashes m_Splashes;
    
    [SerializeField] protected float m_Width = 10.0f;
    
    [SerializeField] protected LayerMask m_CollisionMask;
    [SerializeField] protected float m_RayLengthFactor = 1.0f;
    
    protected Particle[] m_Particles;
    
    [SerializeField] protected float m_RaindropSpeed = 30.0f;
    [SerializeField] protected float m_MaxRaindropDuration = 2.0f;
    [SerializeField] protected float m_MaxRainAngle = 30.0f;
    protected Quaternion m_RainRotation;
    
    [SerializeField] protected float m_RainSpacing = 0.1f;
    [SerializeField] protected float m_DropInterval = 0.02f;
    protected float m_LastDropEmissionTime;
    protected bool m_AlternateRow = false;
    
    protected WindArea[] m_WindAreas;
    
    protected void Start()
    {
        m_WindAreas = (WindArea[])FindObjectsOfType(typeof(WindArea));
    }
    
    protected void Update()
    {
        float spacing = m_Width * m_RainSpacing * 0.5f;
        Vector3 position = transform.position;
        position.x = Mathf.Floor(Camera.main.transform.position.x / spacing) * spacing + Time.time % spacing;
        
        if(m_AlternateRow)
            position.x += spacing * 0.5f;
        
        transform.position = position;
        
        m_RainRotation = Quaternion.AngleAxis((Mathf.Sin(Time.time) + Mathf.Sin((Time.time + 0.25f) * 0.41f)) * 0.5f * m_MaxRainAngle, Vector3.forward);
        
        if(Time.time > m_LastDropEmissionTime + m_DropInterval)
        {
            AddRowOfRaindrops(m_RainSpacing);
            m_LastDropEmissionTime = Time.time;
            
            m_AlternateRow = !m_AlternateRow;
        }
        
        m_Particles = m_ParticleEmitter.particles;
        MoveParticles(Time.deltaTime);
        m_ParticleEmitter.particles = m_Particles;
    }
    
    protected void MoveParticles(float deltaTime)
    {
        for(int i = 0; i < m_Particles.Length; ++i)
        {
            foreach(var windArea in m_WindAreas)
                m_Particles[i].velocity += windArea.RainForceForPoint(m_Particles[i].position) * deltaTime;
            
            m_Particles[i].position += m_Particles[i].velocity * deltaTime;
            m_Particles[i].energy -= deltaTime;
            
            Vector3 direction = m_Particles[i].velocity * Time.deltaTime * m_RayLengthFactor;
            
//          Debug.DrawRay(m_Particles[i].position - direction, direction, Color.cyan, 0.0f);
            
            RaycastHit hit;
            if(Physics.Raycast(m_Particles[i].position - direction, direction, out hit, m_Particles[i].velocity.magnitude * deltaTime, m_CollisionMask))
            {
                m_Particles[i].energy = 0.0f;
                
                m_Splashes.AddSplash(hit.point, hit.normal, 0.2f);
                
                if(hit.collider.gameObject.layer == Layer.WettableIndex)
                {
                    if(hit.rigidbody.gameObject.layer == Layer.PlayerIndex)
                        Game.Wetness += 1.0f;
                    
                    hit.rigidbody.SendMessage("HitByRain");
                }
            }
        }
    }
    
    protected void AddRaindrop()
    {
        m_ParticleEmitter.Emit(GetRandomStartPosition(), m_RainRotation * (Vector3.up * -m_RaindropSpeed),
            Random.Range(m_ParticleEmitter.minSize, m_ParticleEmitter.maxSize), m_MaxRaindropDuration, Color.white);
    }
    
    protected void AddRowOfRaindrops(float spacing)
    {
        for(float x = -1.0f; x <= 1.0f; x += spacing)
        {
            m_ParticleEmitter.Emit(GetStartPositionFromFactor(x), m_RainRotation * (Vector3.up * -m_RaindropSpeed),
                Random.Range(m_ParticleEmitter.minSize, m_ParticleEmitter.maxSize), m_MaxRaindropDuration, Color.white);
        }
    }
    
    protected Vector3 GetRandomStartPosition()
    {
        return GetStartPositionFromFactor(Random.Range(-1.0f, 1.0f));
    }
    
    protected Vector3 GetStartPositionFromFactor(float factor)
    {
        return transform.position + transform.right * m_Width * 0.5f * factor;
    }
    
    protected void OnDrawGizmosSelected()
    {
        Vector3 halfWidth = transform.right * m_Width;
        Gizmos.color = Color.blue;
        Gizmos.DrawLine(transform.position + halfWidth * -0.5f, transform.position + halfWidth * 0.5f);
    }
}