【Unity API】射线相关：Ray Raycast

冷不防 2023-09-25 21:23 16阅读 0赞

**写在前面**

【Unity API】系列！记录实现效果一路上遇到的Unity API，仅作个人学习记录。

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在Unity里写工具时，总有场景需要用到两点发出射线求交的函数，Unity提供了一些API方便我们使用！例如最近在实现一个光晕效果的工具：

*  需要根据光源位置和相机参数确定光源方向
 *  射线求交判断遮挡

脚本里就用到了

*  UnityEngine.Ray
 *  Physics.Raycast

## 1 Ray ##

官方手册：[UnityEngine.Ray - Unity 脚本 API][UnityEngine.Ray - Unity _ API]

关于射线的是一整个struct，首先是通过发出点origin+射线方向确定一个Struct Ray：

//
        // 摘要:
        //     Representation of rays.
        public struct Ray : IFormattable
        {
            //
            // 摘要:
            //     Creates a ray starting at origin along direction.
            //
            // 参数:
            //   origin:
            //
            //   direction:
            public Ray(Vector3 origin, Vector3 direction);
    
            //
            // 摘要:
            //     The origin point of the ray.
            public Vector3 origin { get; set; }
            //
            // 摘要:
            //     The direction of the ray.
            public Vector3 direction { get; set; }
    
            //
            // 摘要:
            //     Returns a point at distance units along the ray.
            //
            // 参数:
            //   distance:
            public Vector3 GetPoint(float distance);
            //
            // 摘要:
            //     Returns a formatted string for this ray.
            //
            // 参数:
            //   format:
            //     A numeric format string.
            //
            //   formatProvider:
            //     An object that specifies culture-specific formatting.
            public override string ToString();
            //
            // 摘要:
            //     Returns a formatted string for this ray.
            //
            // 参数:
            //   format:
            //     A numeric format string.
            //
            //   formatProvider:
            //     An object that specifies culture-specific formatting.
            public string ToString(string format);
            //
            // 摘要:
            //     Returns a formatted string for this ray.
            //
            // 参数:
            //   format:
            //     A numeric format string.
            //
            //   formatProvider:
            //     An object that specifies culture-specific formatting.
            public string ToString(string format, IFormatProvider formatProvider);
        }

[\[Unity\]教程------Ray(射线）的基本使用][Unity_------Ray]这个文章详细写了怎么通过射线检测碰撞物体。

再看看实现光晕，首先需要计算光晕方向

Ray ray = new Ray(m_GameCamera.transform.position, position);

然后Raycast（后面会提到）进行射线遮挡判断

if(Physics.Raycast(ray, out hit))
    {
        ...
    }

## 2 Raycast ##

官方手册:[Physics-Raycast - Unity 脚本 API][Physics-Raycast - Unity _ API]

public static bool Raycast (Vector3 origin, Vector3 direction, float maxDistance= Mathf.Infinity, int layerMask= DefaultRaycastLayers, QueryTriggerInteraction queryTriggerInteraction= QueryTriggerInteraction.UseGlobal);

文档中对这个API的描述为：向场景中的所有碰撞体投射一条射线，该射线起点为 /origin/，朝向 /direction/，长度为 /maxDistance/

返回的值：返回的是一个bool变量，如果射线检测道碰撞机就返回true，否则返回false

RaycastHit hit;
            // Does the ray intersect any objects excluding the player layer
            if (Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, Mathf.Infinity, layerMask))
            {
                Debug.DrawRay(transform.position, transform.TransformDirection(Vector3.forward) * hit.distance, Color.yellow);
                Debug.Log("Did Hit");
            }
            else
            {
                Debug.DrawRay(transform.position, transform.TransformDirection(Vector3.forward) * 1000, Color.white);
                Debug.Log("Did not Hit");
            }

### RaycastHit ###

[NativeHeaderAttribute("Modules/Physics/RaycastHit.h")]
        [NativeHeaderAttribute("Runtime/Interfaces/IRaycast.h")]
        [NativeHeaderAttribute("PhysicsScriptingClasses.h")]
        [UsedByNativeCodeAttribute]
        public struct RaycastHit
        {
            //
            // 摘要:
            //     The Collider that was hit.
            public Collider collider { get; }
            //
            // 摘要:
            //     Instance ID of the Collider that was hit.
            public int colliderInstanceID { get; }
            //
            // 摘要:
            //     The impact point in world space where the ray hit the collider.
            public Vector3 point { get; set; }
            //
            // 摘要:
            //     The normal of the surface the ray hit.
            public Vector3 normal { get; set; }
            //
            // 摘要:
            //     The barycentric coordinate of the triangle we hit.
            public Vector3 barycentricCoordinate { get; set; }
            //
            // 摘要:
            //     The distance from the ray's origin to the impact point.
            public float distance { get; set; }
            //
            // 摘要:
            //     The index of the triangle that was hit.
            public int triangleIndex { get; }
            //
            // 摘要:
            //     The uv texture coordinate at the collision location.
            public Vector2 textureCoord { get; }
            //
            // 摘要:
            //     The secondary uv texture coordinate at the impact point.
            public Vector2 textureCoord2 { get; }
            //
            // 摘要:
            //     The Transform of the rigidbody or collider that was hit.
            public Transform transform { get; }
            //
            // 摘要:
            //     The Rigidbody of the collider that was hit. If the collider is not attached to
            //     a rigidbody then it is null.
            public Rigidbody rigidbody { get; }
            //
            // 摘要:
            //     The ArticulationBody of the collider that was hit. If the collider is not attached
            //     to an articulation body then it is null.
            public ArticulationBody articulationBody { get; }
            //
            // 摘要:
            //     The uv lightmap coordinate at the impact point.
            public Vector2 lightmapCoord { get; }
            [EditorBrowsable(EditorBrowsableState.Never)]
            [Obsolete("Use textureCoord2 instead. (UnityUpgradable) -> textureCoord2")]
            public Vector2 textureCoord1 { get; }
        }

其中，RaycastHit也是一个围绕Raycast定义的结构体，感觉每个定义了Raycast的脚本都会定义个RaycastHit再给他out出来（即使后面不用到），感觉应该是个固定的、不能更改的写法吧。

[Unity学习之Physic.Raycast(射线检测)个人理解分享][Unity_Physic.Raycast]这篇博客演示了碰撞检测的应用。

[UnityEngine.Ray - Unity _ API]: https://docs.unity.cn/cn/2019.4/ScriptReference/Ray.html
[Unity_------Ray]: https://blog.csdn.net/qq_36251561/article/details/119174801
[Physics-Raycast - Unity _ API]: https://docs.unity.cn/cn/2019.4/ScriptReference/Physics.Raycast.html
[Unity_Physic.Raycast]: https://blog.csdn.net/Mars___Z/article/details/89313004