Unity跑酷扭曲shader

1.这个是用来跑酷场景的跑道扭曲的效果。参数Offset不宜设置太高，因为扭曲太高了，它只是把显示图片给予矩阵旋转，但是三角形顶点还是摄像机外，所以使用的时候，会因为顶点不在摄像机里面而在跑酷过程突然给消失（摄像机裁剪）。

Shader "Customs/Curved" {
    Properties {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _QOffset ("Offset", Vector) = (11,-1,0,0)
        _Color ("Main Color", Color) = (1,1,1,1)
        _Brightness ("Brightness", Float) = 1.8
        _Dist ("Distance", Float) = 100.0
        _FogColor("FogColor", Color) = (0.87,0.87,0.87,1)
        _FogDensity("FogDensity", Float) = 0.1
        _FogRange("FogRange", Float) = 300
        _Cut("Cut", range(0,1)) = 0

    }

    SubShader {
        Tags {"RenderType"="TransparentCutOut"}
        //blend srcalpha oneminussrcalpha
        Cull off

        zwrite on

        CGPROGRAM
        #pragma surface surf Lambert vertex:vert alphatest:_Cut
        struct Input 
        {
             float2 uv_MainTex;
        };

        sampler2D _MainTex;
        float4 _QOffset;
        float _Dist;
        float _Insensitive;
        float _Brightness;
        float4 _Color;

        void vert (inout appdata_full v) 
        {

            float4 vPos = mul (UNITY_MATRIX_MV, v.vertex);

            float xsmeh=sin(_WorldSpaceCameraPos.z/120);

            float zOff = vPos.z/_Dist;

            vPos += _QOffset*zOff*zOff;

            v.vertex = mul(transpose(UNITY_MATRIX_IT_MV), vPos);
            #if SHADER_API_GLES
                v.vertex.xyz*= 1.0;
            #endif
        }

        void surf (Input IN, inout SurfaceOutput o) 
        {
            o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb * _Brightness * _Color;
            float alpha = tex2D (_MainTex, IN.uv_MainTex).a;
            o.Alpha = alpha;  
        }

        ENDCG
    }

    Fallback "Diffuse"
}