Physics.RaycastNonAlloc 是 Unity 中用于 3D 物理射线检测的高性能方法，它是 Physics.Raycast 的非分配版本。

方法签名

public static int RaycastNonAlloc(Ray ray, RaycastHit[] results, float maxDistance = Mathf.Infinity, int layerMask = DefaultRaycastLayers, QueryTriggerInteraction queryTriggerInteraction = QueryTriggerInteraction.UseGlobal)public static int RaycastNonAlloc(Vector3 origin, Vector3 direction, RaycastHit[] results, float maxDistance = Mathf.Infinity, int layerMask = DefaultRaycastLayers, QueryTriggerInteraction queryTriggerInteraction = QueryTriggerInteraction.UseGlobal)

参数说明

• ray/origin+direction: 射线或起点+方向
• results: 预分配的 RaycastHit 数组
• maxDistance: 射线最大距离
• layerMask: 层级掩码
• queryTriggerInteraction: 是否检测触发器

数组大小限制的重要性

问题说明

当可能击中的目标数量超过 results 数组的大小时，超出容量的击中目标将被忽略，这可能导致重要的碰撞检测被遗漏。

演示示例

using UnityEngine;public class RaycastLimitationDemo : MonoBehaviour
{[SerializeField] private int arraySize = 3;[SerializeField] private float rayDistance = 100f;private RaycastHit[] smallArray;private RaycastHit[] largeArray;void Start(){smallArray = new RaycastHit[arraySize];      // 小数组largeArray = new RaycastHit[50];             // 大数组}void Update(){if (Input.GetKeyDown(KeyCode.Space)){CompareRaycastResults();}}void CompareRaycastResults(){Vector3 origin = transform.position;Vector3 direction = transform.forward;// 使用小数组检测int smallHitCount = Physics.RaycastNonAlloc(origin, direction, smallArray, rayDistance);// 使用大数组检测int largeHitCount = Physics.RaycastNonAlloc(origin, direction, largeArray, rayDistance);Debug.Log($"小数组(大小:{arraySize})检测到: {smallHitCount} 个目标");Debug.Log($"大数组(大小:50)检测到: {largeHitCount} 个目标");if (largeHitCount > smallHitCount){Debug.LogWarning($"⚠️ 遗漏了 {largeHitCount - smallHitCount} 个目标！");// 显示被遗漏的目标for (int i = smallHitCount; i < largeHitCount; i++){Debug.LogWarning($"遗漏目标: {largeArray[i].collider.name} (距离: {largeArray[i].distance:F2})");}}}
}

实际问题场景

1. 子弹穿透系统问题

public class BulletPenetration : MonoBehaviour
{[SerializeField] private int maxPenetrations = 3;private RaycastHit[] hits;void Start(){// ❌ 错误：数组太小，可能遗漏目标hits = new RaycastHit[maxPenetrations];}public void FireBullet(Vector3 origin, Vector3 direction, float range){int hitCount = Physics.RaycastNonAlloc(origin, direction, hits, range);Debug.Log($"检测到 {hitCount} 个目标");// 问题：如果路径上有5个目标，但数组只能容纳3个// 最后2个目标不会被检测到，即使它们在射线路径上for (int i = 0; i < hitCount && i < maxPenetrations; i++){ProcessHit(hits[i]);}}void ProcessHit(RaycastHit hit){Debug.Log($"击中: {hit.collider.name}");}
}

2. 改进的解决方案

public class ImprovedBulletPenetration : MonoBehaviour
{[SerializeField] private int maxPenetrations = 3;[SerializeField] private int maxDetectionTargets = 20; // 增大检测容量private RaycastHit[] allHits;void Start(){// ✅ 正确：使用更大的数组确保不遗漏目标allHits = new RaycastHit[maxDetectionTargets];}public void FireBullet(Vector3 origin, Vector3 direction, float range){int totalHits = Physics.RaycastNonAlloc(origin, direction, allHits, range);Debug.Log($"路径上共检测到 {totalHits} 个目标");// 根据距离排序（RaycastNonAlloc 默认已按距离排序）int processedHits = 0;for (int i = 0; i < totalHits && processedHits < maxPenetrations; i++){if (CanPenetrate(allHits[i])){ProcessHit(allHits[i]);processedHits++;}else{// 遇到无法穿透的目标，停止处理ProcessHit(allHits[i]);break;}}// 显示未处理的目标（因为穿透限制）if (totalHits > processedHits){Debug.Log($"因穿透限制，忽略了后续 {totalHits - processedHits} 个目标");}}bool CanPenetrate(RaycastHit hit){// 检查材质或标签决定是否可穿透return hit.collider.CompareTag("Penetrable");}void ProcessHit(RaycastHit hit){Debug.Log($"处理击中: {hit.collider.name} (距离: {hit.distance:F2})");}
}

3. 动态数组大小管理

public class DynamicRaycastSystem : MonoBehaviour
{private RaycastHit[] raycastBuffer;private int currentBufferSize = 10;private const int MAX_BUFFER_SIZE = 100;void Start(){raycastBuffer = new RaycastHit[currentBufferSize];}public RaycastHit[] PerformRaycast(Vector3 origin, Vector3 direction, float distance){int attempts = 0;int hitCount;do{hitCount = Physics.RaycastNonAlloc(origin, direction, raycastBuffer, distance);// 如果数组已满，说明可能还有更多目标if (hitCount == raycastBuffer.Length && currentBufferSize < MAX_BUFFER_SIZE){// 扩大数组currentBufferSize = Mathf.Min(currentBufferSize * 2, MAX_BUFFER_SIZE);raycastBuffer = new RaycastHit[currentBufferSize];Debug.LogWarning($"扩大射线检测缓冲区至 {currentBufferSize}");attempts++;}else{break;}}while (attempts < 3); // 最多尝试3次扩展// 返回实际击中的结果RaycastHit[] results = new RaycastHit[hitCount];System.Array.Copy(raycastBuffer, results, hitCount);return results;}
}

最佳实践建议

1. 合理估算数组大小

public class RaycastBestPractices : MonoBehaviour
{// 根据场景复杂度设置缓冲区大小private RaycastHit[] hits;void Start(){// 分析你的场景：// - 最密集区域可能有多少个碰撞器？// - 射线最长距离内可能遇到多少目标？// - 加上安全余量int estimatedMaxTargets = AnalyzeSceneComplexity();int safetyBuffer = estimatedMaxTargets / 2;int bufferSize = estimatedMaxTargets + safetyBuffer;hits = new RaycastHit[bufferSize];Debug.Log($"射线检测缓冲区大小: {bufferSize}");}int AnalyzeSceneComplexity(){// 简单的场景复杂度分析Collider[] allColliders = FindObjectsOfType<Collider>();// 可以根据场景大小、碰撞器密度等因素计算return Mathf.Max(20, allColliders.Length / 10);}
}

2. 性能监控

public class RaycastPerformanceMonitor : MonoBehaviour
{private RaycastHit[] hits = new RaycastHit[50];private int maxHitsRecorded = 0;void Update(){if (Input.GetMouseButton(0)){PerformMonitoredRaycast();}}void PerformMonitoredRaycast(){Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);int hitCount = Physics.RaycastNonAlloc(ray, hits, 100f);// 记录最大击中数if (hitCount > maxHitsRecorded){maxHitsRecorded = hitCount;Debug.Log($"新的最大击中数记录: {maxHitsRecorded}");}// 检查是否接近数组限制if (hitCount >= hits.Length * 0.8f){Debug.LogWarning($"射线检测接近缓冲区限制！当前: {hitCount}/{hits.Length}");}}void OnGUI(){GUI.Label(new Rect(10, 10, 300, 20), $"最大击中记录: {maxHitsRecorded}");GUI.Label(new Rect(10, 30, 300, 20), $"缓冲区大小: {hits.Length}");}
}

总结

使用 Physics.RaycastNonAlloc 时，数组大小的选择至关重要：

1. 过小的数组：会导致遗漏目标，可能影响游戏逻辑
2. 过大的数组：浪费内存，但确保完整性
3. 最佳实践：根据场景复杂度合理估算，加上安全余量
4. 监控机制：在开发阶段监控实际使用情况，调整数组大小

记住：宁可数组稍大一些，也不要因为大小不足而遗漏重要的碰撞检测。