Unity shader学习之Grab Pass实现玻璃效果

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/Glass"
{
Properties
{
_NormalMap("Normal Map", 2D) = "bump" {}
_Distortion("Distortion", Range(0, 100)) = 50
}

SubShader
{
Tags
{
"Queue" = "Transparent"
"RenderType" = "Transparent"
}

GrabPass { "_GrabTex" }

Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"

sampler2D _GrabTex;
float4 _GrabTex_TexelSize;
sampler2D _NormalMap;
float _Distortion;

struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};

struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
float4 scrPos : TEXCOORD1;
};

v2f vert(appdata v)
{
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv = v.uv;
o.scrPos = ComputeGrabScreenPos(o.pos);
return o;
}

fixed4 frag(v2f i) : SV_TARGET
{
float3 bump = UnpackNormal(tex2D(_NormalMap, i.uv));
float2 offset = bump.xy * _GrabTex_TexelSize.xy * _Distortion;
fixed4 albedo = tex2D(_GrabTex, (i.scrPos.xy + offset) / i.scrPos.w);
return albedo;
}

ENDCG
}
}
}