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前言

我们使用之前的棋盘格作为测试Shader来添加雾效。

• Unity中 URP 下的棋盘格Shader

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一、URP下Shader支持雾效的步骤

1、添加雾效变体

#pragma multi_compile_fog

2、在Varying结构体中添加雾效因子

float fogCoord : TEXCOORD2;

3、在顶点着色器中，我们使用内置函数得到雾效因子

o.fogCoord = ComputeFogFactor(o.vertexCS.z);

4、在片元着色器中，把输出颜色 和 雾效因子混合输出

col.rgb = MixFog(col,i.fogCoord);

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二、在Unity中打开雾效

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三、测试代码

Shader "MyShader/URP/P3_8"
{
    Properties
    {
        _Repeat("Repeat",Float) = 0
        _Color("Color",Color) = (1,1,1,1)
    }
    SubShader
    {
        Tags
        {
            "PenderPipeline"="UniversalPipeline"
            "RenderType"="Opaque"
            "Queue"="Geometry"
        }
        Cull Front
        Pass
        {
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog

            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"

            struct Attribute
            {
                float3 vertexOS : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct Varying
            {
                float3 vertexOS : TEXCOORD0;
                float4 vertexCS : SV_POSITION;
                float2 uv : TEXCOORD1;
                float fogCoord : TEXCOORD2;
            };

            CBUFFER_START(UnityPerMaterial)
                float _Repeat;
                float4 _Color;
            CBUFFER_END

            Varying vert(Attribute v)
            {
                Varying o;
                o.vertexOS = v.vertexOS;
                o.vertexCS = TransformObjectToHClip(v.vertexOS);
                o.uv = v.uv * _Repeat;
                o.fogCoord = ComputeFogFactor(o.vertexCS.z);
                return o;
            }

            half4 frag(Varying i) : SV_Target
            {
                /*half4 col1;
                half4 col2;
                if(i.uv.x < 0.5)
                    col1 = 0;
                else
                    col1 = 0.5;
                if(i.uv.y < 0.5)
                    col2 = 0;
                else
                    col2 = 0.5;*/
                half4 col;
                float2 uv = floor(i.uv * 2) * 0.5;
                col = frac(uv.x + uv.y) * 2;
                float mask = i.vertexOS.y;
                col = col * _Color + mask;
                col.rgb = MixFog(col,i.fogCoord);
                return col;
            }
            ENDHLSL
        }
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
            "Queue"="Geometry"
        }
        Cull Front
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float3 vertexOS : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float3 vertexOS : TEXCOORD0;
                float4 vertexCS : SV_POSITION;
                float2 uv : TEXCOORD1;
            };

            float _Repeat;
            float4 _Color;

            v2f vert(appdata v)
            {
                v2f o;
                o.vertexOS = v.vertexOS;
                o.vertexCS = UnityObjectToClipPos(v.vertexOS);
                o.uv = v.uv * _Repeat;
                return o;
            }

            half4 frag(v2f i) : SV_Target
            {
                half4 col;
                float2 uv = floor(i.uv * 2) * 0.5;
                col = frac(uv.x + uv.y) * 2;
                float mask = i.vertexOS.y;
                col = col * _Color + mask;
                return col;
            }
            ENDCG
        }
    }
}