这里面我转一个镜面反射，再阐述一些遇到的问题，先建立以个Shader，名字可以叫做MirrorReflection，脚本如下：
Shader "FX/Mirror Reflection"
{Properties
{_MainTex("Base(RGB)",2D)="white"{}
  _ReflectionTex("Reflection",2D)="white"{TexGen ObjectLinear}
}

        // two texture cards: full thing
Subshader
{Pass
         {SetTexture[_MainTex]{combine texture}
   SetTexture[_ReflectionTex]{matrix [_ProjMatrix] combine texture*previous}
  }
}

        // fallback: just main texture
        Subshader
{Pass
  {SetTexture [_MainTex]{combine texture}
  }
        }
}

在建立一个cs脚本，名字叫做MirrorReflection，脚本如下：
using unityEngine;
using System.Collections;

//实际上 This is in fact just the Water script from Pro Standard Assets,

// just with refraction stuff removed.



[ExecuteInEditMode]// Make mirror live-update even when not in play mode
public class MirrorReflection:MonoBehaviour
{public bool m_DisablePixelLights=true;
public int m_TextureSize=256;
        public float m_ClipPlaneOffset=0.07f;
        public LayerMask m_ReflectLayers=-1;
        private Hashtable m_ReflectionCameras=new Hashtable(); // Camera ->Camera table
        private RenderTexture m_ReflectionTexture=null;
        private int m_OldReflectionTextureSize=0;
        private static bool s_InsideRendering=false;

        // This is called when it's known that the object will be rendered by some
        // camera. We render reflections and do other updates here.
        // Because the script executes in edit mode,reflections for the scene view
        // camera will just work!
        public void OnWillRenderObject()
        {if(!enabled || !renderer || !renderer.sharedMaterial || !renderer.enabled )return;
                Camera cam=Camera.current;
                if(!cam )return;

                // Safeguard from recursive reflections.
                if(s_InsideRendering )return;

                s_InsideRendering=true;

                Camera reflectionCamera;

                CreateMirrorObjects(cam,out reflectionCamera );

                // find out the reflection plane:position and normal in world space
                Vector3 pos=transform.position;
                Vector3 normal=transform.up;

                // Optionally disable pixel lights for reflection
                int oldPixelLightCount=QualitySettings.pixelLightCount;
                if(m_DisablePixelLights )QualitySettings.pixelLightCount=0;

                UpdateCameraModes(cam,reflectionCamera );

                // Render reflection
                // Reflect camera around reflection plane
                float d=-Vector3.Dot(normal,pos)-m_ClipPlaneOffset;

                Vector4 reflectionPlane=new Vector4(normal.x,normal.y,normal.z,d);

                Matrix4x4 reflection=Matrix4x4.zero;

                CalculateReflectionMatrix(ref reflection,reflectionPlane);

Vector3 oldpos=cam.transform.position;

Vector3 newpos=reflection.MultiplyPoint(oldpos );

reflectionCamera.worldToCameraMatrix=cam.worldToCameraMatrix * reflection;



// Setup oblique projection matrix so that near plane is our reflection

// plane. This way we clip everything below/above it for free.

Vector4 clipPlane=CameraSpacePlane(reflectionCamera,pos,normal,1.0f );

Matrix4x4 projection=cam.projectionMatrix;

CalculateObliqueMatrix(ref projection,clipPlane);

reflectionCamera.projectionMatrix=projection;



reflectionCamera.cullingMask=~(1<<4)& m_ReflectLayers.value; // never render water layer

reflectionCamera.targetTexture=m_ReflectionTexture;

GL.SetRevertBackfacing(true);

reflectionCamera.transform.position=newpos;

Vector3 euler=cam.transform.eulerAngles;

reflectionCamera.transform.eulerAngles=new Vector3(0,euler.y,euler.z);

reflectionCamera.Render();

reflectionCamera.transform.position=oldpos;

GL.SetRevertBackfacing(false);

Material[]materials=renderer.sharedMaterials;

foreach(Material mat in materials ){

if(mat.HasProperty("_ReflectionTex"))

mat.SetTexture("_ReflectionTex",m_ReflectionTexture );

}



// Set matrix on the shader that transforms UVs from object space into screen

// space. We want to just project reflection texture on screen.

Matrix4x4 scaleOffset=Matrix4x4.TRS(

new Vector3(0.5f,0.5f,0.5f),Quaternion.identity,new Vector3(0.5f,0.5f,0.5f));

Vector3 scale=transform.lossyScale;

Matrix4x4 mtx=transform.localToWorldMatrix * Matrix4x4.Scale(new Vector3(1.0f/scale.x,1.0f/scale.y,1.0f/scale.z));

mtx=scaleOffset * cam.projectionMatrix * cam.worldToCameraMatrix * mtx;

foreach(Material mat in materials ){

mat.SetMatrix("_ProjMatrix",mtx );

}



// Restore pixel light count

if(m_DisablePixelLights )

QualitySettings.pixelLightCount=oldPixelLightCount;



s_InsideRendering=false;

}





// Cleanup all the objects we possibly have created

void OnDisable()

{

if(m_ReflectionTexture ){

DestroyImmediate(m_ReflectionTexture );

m_ReflectionTexture=null;

}

foreach(DictionaryEntry kvp in m_ReflectionCameras )

DestroyImmediate(((Camera)kvp.Value).gameObject );

m_ReflectionCameras.Clear();

}





private void UpdateCameraModes(Camera src,Camera dest )

{

if(dest==null )

return;

// set camera to clear the same way as current camera

dest.clearFlags=src.clearFlags;

dest.backgroundColor=src.backgroundColor;

if(src.clearFlags==CameraClearFlags.Skybox )

{

Skybox sky=src.GetComponent(typeof(Skybox))as Skybox;

Skybox mysky=dest.GetComponent(typeof(Skybox))as Skybox;

if(!sky || !sky.material )

{

mysky.enabled=false;

}

else

{

mysky.enabled=true;

mysky.material=sky.material;

}

}

// update other values to match current camera.

// even if we are supplying custom camera&projection matrices,

// some of values are used elsewhere(e.g. skybox uses far plane)

dest.farClipPlane=src.farClipPlane;

dest.nearClipPlane=src.nearClipPlane;

dest.orthographic=src.orthographic;

dest.fieldOfView=src.fieldOfView;

dest.aspect=src.aspect;

dest.orthographicSize=src.orthographicSize;

}



// On-demand create any objects we need

private void CreateMirrorObjects(Camera currentCamera,out Camera reflectionCamera )

{

reflectionCamera=null;



// Reflection render texture

if(!m_ReflectionTexture || m_OldReflectionTextureSize !=m_TextureSize )

{

if(m_ReflectionTexture )

DestroyImmediate(m_ReflectionTexture );

m_ReflectionTexture=new RenderTexture(m_TextureSize,m_TextureSize,16 );

m_ReflectionTexture.name="__MirrorReflection" + GetInstanceID();

m_ReflectionTexture.isPowerOfTwo=true;

m_ReflectionTexture.hideFlags=HideFlags.DontSave;

m_OldReflectionTextureSize=m_TextureSize;

}



// Camera for reflection

reflectionCamera=m_ReflectionCameras[currentCamera]as Camera;

if(!reflectionCamera )// catch both not-in-dictionary and in-dictionary-but-deleted-GO

{

GameObject go=new GameObject("Mirror Refl Camera id" + GetInstanceID()+ " for " + currentCamera.GetInstanceID(),typeof(Camera),typeof(Skybox));

reflectionCamera=go.camera;

reflectionCamera.enabled=false;

reflectionCamera.transform.position=transform.position;

reflectionCamera.transform.rotation=transform.rotation;

reflectionCamera.gameObject.AddComponent("FlareLayer");

go.hideFlags=HideFlags.HideAndDontSave;

m_ReflectionCameras[currentCamera]=reflectionCamera;

}

}

// Extended sign:returns -1,0 or 1 based on sign of a
private static float sgn(float a)
{if(a>0.0f)return 1.0f;
        if(a<0.0f)return -1.0f;
        return 0.0f;
}
// Given position/normal of the plane,calculates plane in camera space.

private Vector4 CameraSpacePlane(Camera cam,Vector3 pos,Vector3 normal,float sideSign)

{

Vector3 offsetPos=pos + normal * m_ClipPlaneOffset;

Matrix4x4 m=cam.worldToCameraMatrix;

Vector3 cpos=m.MultiplyPoint(offsetPos );

Vector3 cnormal=m.MultiplyVector(normal ).normalized * sideSign;

return new Vector4(cnormal.x,cnormal.y,cnormal.z,-Vector3.Dot(cpos,cnormal));

}



//调整给定的射影矩阵以便最近的平面Adjusts the given projection matrix so that near plane is the given clipPlane
// clipPlane is given in camera space. See article in Game Programming Gems 5.
private static void CalculateObliqueMatrix(ref Matrix4x4 projection,Vector4 clipPlane)
{Vector4 q=projection.inverse * new Vector4(sgn(clipPlane.x),sgn(clipPlane.y),1.0f,1.0f);
        Vector4 c=clipPlane *(2.0F /(Vector4.Dot(clipPlane,q)));
        // third row=clip plane -fourth row
        projection[2]=c.x -projection[3];
        projection[6]=c.y -projection[7];
        projection[10]=c.z -projection[11];
        projection[14]=c.w -projection[15];
}

//围绕给定的平面计算折射矩阵
private static void CalculateReflectionMatrix(ref Matrix4x4 reflectionMat,Vector4 plane)
{reflectionMat.m00=(1F -2F*plane[0]*plane[0]);
        reflectionMat.m01=(-2F*plane[0]*plane[1]);
        reflectionMat.m02=(-2F*plane[0]*plane[2]);
        reflectionMat.m03=(-2F*plane[3]*plane[0]);

        reflectionMat.m10=(-2F*plane[1]*plane[0]);
        reflectionMat.m11=(1F -2F*plane[1]*plane[1]);
        reflectionMat.m12=(-2F*plane[1]*plane[2]);
        reflectionMat.m13=(-2F*plane[3]*plane[1]);

        reflectionMat.m20=(-2F*plane[2]*plane[0]);
        reflectionMat.m21=(-2F*plane[2]*plane[1]);
        reflectionMat.m22=(1F -2F*plane[2]*plane[2]);
        reflectionMat.m23=(-2F*plane[3]*plane[2]);

        reflectionMat.m30=0F;
        reflectionMat.m31=0F;
        reflectionMat.m32=0F;
        reflectionMat.m33=1F;
        }
}

值得注意的是，地面，或者镜面尽量用U3d里面自建的plane,把shader和cs脚本直接赋予到该plane上就出效果了。其他物体不必赋予。

好吧，我表示看的眼睛有点花了

谢谢分享了！给需要的人