FixedPhysicsRaycaster.cs

using System.Collections.Generic;
using UnityEngine.UI;

namespace UnityEngine.EventSystems
{
	/// <summary>
	/// Simple event system using physics raycasts.
	/// </summary>
	[AddComponentMenu("Event/Physics Raycaster (Fixed)")]
	[RequireComponent(typeof(Camera))]
	public class FixedPhysicsRaycaster : BaseRaycaster
	{
		/// <summary>
		/// Const to use for clarity when no event mask is set
		/// </summary>
		protected const int kNoEventMaskSet = -1;

		protected Camera m_EventCamera;

		/// <summary>
		/// Layer mask used to filter events. Always combined with the camera's culling mask if a camera is used.
		/// </summary>
		[SerializeField]
		protected LayerMask m_EventMask = kNoEventMaskSet;

		/// <summary>
		/// The max number of intersections allowed. 0 = allocating version anything else is non alloc.
		/// </summary>
		[SerializeField]
		protected int m_MaxRayIntersections = 0;
		protected int m_LastMaxRayIntersections = 0;

		RaycastHit[] m_Hits;

		protected FixedPhysicsRaycaster()
		{ }

		public override Camera eventCamera
		{
			get
			{
				if (m_EventCamera == null)
					m_EventCamera = GetComponent<Camera>();
				return m_EventCamera ?? Camera.main;
			}
		}


		/// <summary>
		/// Depth used to determine the order of event processing.
		/// </summary>
		public virtual int depth
		{
			get { return (eventCamera != null) ? (int)eventCamera.depth : 0xFFFFFF; }
		}

		/// <summary>
		/// Event mask used to determine which objects will receive events.
		/// </summary>
		public int finalEventMask
		{
			get { return (eventCamera != null) ? eventCamera.cullingMask & m_EventMask : kNoEventMaskSet; }
		}

		/// <summary>
		/// Layer mask used to filter events. Always combined with the camera's culling mask if a camera is used.
		/// </summary>
		public LayerMask eventMask
		{
			get { return m_EventMask; }
			set { m_EventMask = value; }
		}

		public int maxRayIntersections
		{
			get { return m_MaxRayIntersections; }
			set { m_MaxRayIntersections = value; }
		}

		protected void ComputeRayAndDistance(PointerEventData eventData, out Ray ray, out float distanceToClipPlane)
		{
			ray = eventCamera.ScreenPointToRay(eventData.position);
			// compensate far plane distance - see MouseEvents.cs
			float projectionDirection = ray.direction.z;
			distanceToClipPlane = Mathf.Approximately(0.0f, projectionDirection)
				? Mathf.Infinity
				: Mathf.Abs((eventCamera.farClipPlane - eventCamera.nearClipPlane) / projectionDirection);
		}

		public override void Raycast(PointerEventData eventData, List<RaycastResult> resultAppendList)
		{
			// Cull ray casts that are outside of the view rect. (case 636595)
			if (eventCamera == null || !eventCamera.pixelRect.Contains(eventData.position))
				return;

			Ray ray;
			float distanceToClipPlane;
			ComputeRayAndDistance(eventData, out ray, out distanceToClipPlane);

			int hitCount = 0;

			if (m_MaxRayIntersections == 0)
			{
				m_Hits = Physics.RaycastAll(ray, distanceToClipPlane, finalEventMask);
				hitCount = m_Hits.Length;
			}
			else
			{
				if (m_LastMaxRayIntersections != m_MaxRayIntersections)
				{
					m_Hits = new RaycastHit[m_MaxRayIntersections];
					m_LastMaxRayIntersections = m_MaxRayIntersections;
				}

				hitCount = Physics.RaycastNonAlloc(ray, m_Hits, distanceToClipPlane, finalEventMask);				
			}

			if (hitCount > 1)
				System.Array.Sort(m_Hits, (r1, r2) => r1.distance.CompareTo(r2.distance));

			if (hitCount != 0)
			{
				for (int b = 0, bmax = hitCount; b < bmax; ++b)
				{
					var result = new RaycastResult
					{
						gameObject = (m_Hits[b].collider ? m_Hits[b].collider.gameObject : null),
						module = this,
						distance = m_Hits[b].distance,
						worldPosition = m_Hits[b].point,
						worldNormal = m_Hits[b].normal,
						screenPosition = eventData.position,
						index = resultAppendList.Count,
						sortingLayer = 0,
						sortingOrder = 0
					};
					resultAppendList.Add(result);
				}
			}
		}
	}
}