[小明学Shader]14.热扭曲效果

1.代码

Shader "AAAA/HeatIsland" {
Properties {
    _MainTex ("Base (RGB)", 2D) = "white" {}
    _OffsetTex ("Shui (RGB)", 2D) = "white" {}
    _ClipTex ("Clip (RGB)", 2D) = "white" {}
    _Speed("速度",range(2,12))=12
    _Range("range",range(0,20))=10
}

SubShader {
    Pass {
        ZTest Always Cull Off ZWrite Off
        Fog { Mode off }
                
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest 
#include "UnityCG.cginc"

uniform sampler2D _MainTex;
uniform sampler2D _OffsetTex;
uniform float _Speed;
uniform float _Range;

struct v2f {
    float4 pos : POSITION;
    float2 uv : TEXCOORD0;
};

v2f vert( appdata_img v )
{
    v2f o;
    o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
    o.uv = v.texcoord;
    return o;
}

float4 frag (v2f i) : COLOR{
    float2 offset = i.uv;
    
    //噪声图的uv随着时间增长一直向下移动
    float2 offsetUV=float2(i.uv.x,i.uv.y-_Time.x*_Speed);
    //计算下移后的uv所对应的color
    float4 shuiColor = tex2D(_OffsetTex, offsetUV);
    //将MainTex的uv进行偏移
    offsetUV = offset + shuiColor.xy/_Range;
    
    return tex2D(_MainTex, offsetUV);
}
ENDCG

    }
}

Fallback off

}

2.效果

3.注意 

　　扭曲的本质是UV偏移,便宜信息写在一张噪声图里而已.