Glass Refraction-截图模拟玻璃效果

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unity Shaders Book/Chapter 10/Glass Refraction" {
   Properties {
       _MainTex ("Main Tex", 2D) = "white" {}
       _BumpMap ("Normal Map", 2D) = "bump" {}
       _Cubemap ("Environment Cubemap", Cube) = "_Skybox" {}
       _Distortion ("Distortion", Range(0, 100)) = 10
       _RefractAmount ("Refract Amount", Range(0.0, 1.0)) = 1.0
   }
   SubShader {
       // We must be transparent, so other objects are drawn before this one.
       Tags { "Queue"="Transparent" "RenderType"="Opaque" }

       // This pass grabs the screen behind the object into a texture.
       // We can access the result in the next pass as _RefractionTex
       GrabPass { "_RefractionTex" }

       Pass {
           CGPROGRAM

           #pragma vertex vert
           #pragma fragment frag

           #include "UnityCG.cginc"

           sampler2D _MainTex;
           float4 _MainTex_ST;
           sampler2D _BumpMap;
           float4 _BumpMap_ST;
           samplerCUBE _Cubemap;
           float _Distortion;
           fixed _RefractAmount;
           sampler2D _RefractionTex;
           float4 _RefractionTex_TexelSize;

           struct a2v {
               float4 vertex : POSITION;
               float3 normal : NORMAL;
               float4 tangent : TANGENT;
               float2 texcoord: TEXCOORD0;
           };

           struct v2f {
               float4 pos : SV_POSITION;
               float4 scrPos : TEXCOORD0;
               float4 uv : TEXCOORD1;
               float4 TtoW0 : TEXCOORD2;
           float4 TtoW1 : TEXCOORD3;
           float4 TtoW2 : TEXCOORD4;
           };

           v2f vert (a2v v) {
               v2f o;
               o.pos = UnityObjectToClipPos(v.vertex);

               o.scrPos = ComputeGrabScreenPos(o.pos);

               o.uv.xy = TRANSFORM_TEX(v.texcoord, _MainTex);
               o.uv.zw = TRANSFORM_TEX(v.texcoord, _BumpMap);

               float3 worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
               fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
               fixed3 worldTangent = UnityObjectToWorldDir(v.tangent.xyz);
               fixed3 worldBinormal = cross(worldNormal, worldTangent) * v.tangent.w;

               o.TtoW0 = float4(worldTangent.x, worldBinormal.x, worldNormal.x, worldPos.x);
               o.TtoW1 = float4(worldTangent.y, worldBinormal.y, worldNormal.y, worldPos.y);
               o.TtoW2 = float4(worldTangent.z, worldBinormal.z, worldNormal.z, worldPos.z);

               return o;
           }

           fixed4 frag (v2f i) : SV_Target {
               float3 worldPos = float3(i.TtoW0.w, i.TtoW1.w, i.TtoW2.w);
               fixed3 worldViewDir = normalize(UnityWorldSpaceViewDir(worldPos));

               // Get the normal in tangent space
               fixed3 bump = UnpackNormal(tex2D(_BumpMap, i.uv.zw));

               // Compute the offset in tangent space
               float2 offset = bump.xy * _Distortion * _RefractionTex_TexelSize.xy;
               i.scrPos.xy = offset * i.scrPos.z + i.scrPos.xy;
               fixed3 refrCol = tex2D(_RefractionTex, i.scrPos.xy/i.scrPos.w).rgb;

               // Convert the normal to world space
               bump = normalize(half3(dot(i.TtoW0.xyz, bump), dot(i.TtoW1.xyz, bump), dot(i.TtoW2.xyz, bump)));
               fixed3 reflDir = reflect(-worldViewDir, bump);
               fixed4 texColor = tex2D(_MainTex, i.uv.xy);
               fixed3 reflCol = texCUBE(_Cubemap, reflDir).rgb * texColor.rgb;z

               fixed3 finalColor = reflCol * (1 - _RefractAmount) + refrCol * _RefractAmount;

               return fixed4(finalColor, 1);
           }

           ENDCG
       }
   }

   FallBack "Diffuse"
}

取自《Unity Shader 入门精要》

玻璃扭曲效果要用切线空间下的法线坐标，因为此时法线的标准方向是(0,0,1)，前面两个数字可以用来做UV扰动

GrabPass { "TextureName" } Unity只会在每帧为第一个使用名为TextureName的纹理的物体执行一次抓取屏幕的操作，而这个纹理可以在其他Pass中被访问。优点是只抓取一次，缺点是用到这个纹理的Pass访问的纹理是一样的。

Glass Refraction-截图模拟玻璃效果

猜你喜欢