---------转自蛮牛“东方喵”分享：http://www.manew.com/thread-91896-1-1.html

Shader "Xffect/heat_distortion" {
Properties {
_NoiseTex ("Noise Texture (RG)", 2D) = "white" {}
_MainTex ("Alpha (A)", 2D) = "white" {}
_HeatTime ("Heat Time", range (0,1.5)) = 1
_HeatForce ("Heat Force", range (0,0.1)) = 0.1
}

Category {
Tags { "Queue"="Transparent+1" "RenderType"="Transparent" }
Blend SrcAlpha OneMinusSrcAlpha
AlphaTest Greater .01
Cull Off Lighting Off ZWrite Off

SubShader {
    GrabPass {                         
        Name "BASE"
        Tags { "LightMode" = "Always" }
    }

    Pass {
        Name "BASE"
        Tags { "LightMode" = "Always" }

CGPROGRAM

pragma vertex vert

pragma fragment frag

pragma fragmentoption ARB_precision_hint_fastest

include "UnityCG.cginc"

struct appdata_t {
float4 vertex : POSITION;
fixed4 color : COLOR;
float2 texcoord: TEXCOORD0;
};

struct v2f {
float4 vertex : POSITION;
float4 uvgrab : TEXCOORD0;
float2 uvmain : TEXCOORD1;
};

float _HeatForce;
float _HeatTime;
float4 _MainTex_ST;
float4 _NoiseTex_ST;
sampler2D _NoiseTex;
sampler2D _MainTex;

v2f vert (appdata_t v)
{
v2f o;
o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
#if UNITY_UV_STARTS_AT_TOP
float scale = -1.0;
#else
float scale = 1.0;
#endif
o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;
o.uvgrab.zw = o.vertex.zw;
o.uvmain = TRANSFORM_TEX( v.texcoord, _MainTex );
return o;
}

sampler2D _GrabTexture;

half4 frag( v2f i ) : COLOR
{

//noise effect
half4 offsetColor1 = tex2D(_NoiseTex, i.uvmain + _Time.xz*_HeatTime);
half4 offsetColor2 = tex2D(_NoiseTex, i.uvmain - _Time.yx*_HeatTime);
i.uvgrab.x += ((offsetColor1.r + offsetColor2.r) - 1) * _HeatForce;
i.uvgrab.y += ((offsetColor1.g + offsetColor2.g) - 1) * _HeatForce;
 

half4 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));
//Skybox's alpha is zero, don't know why.
col.a = 1.0f;
half4 tint = tex2D( _MainTex, i.uvmain);

return col*tint;

}
ENDCG
}
}

// ------------------------------------------------------------------
// Fallback for older cards and Unity non-Pro
 
SubShader {
    Blend DstColor Zero
    Pass {
        Name "BASE"
        SetTexture [_MainTex] { combine texture }
    }
}

}
}