Unity shader学习之阴影，衰减统一处理

使用unity AutoLight.cginc文件里的内置函数 UNITY_LIGHT_ATTENUATION

shader如下：

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

Shader "Custom/Forward Rendering"
{
    Properties
    {
        _MainTex("Main Texture", 2D) = "white" {}
        _Specular("Specular", Color) = (,,,)
        _Gloss("Gloss", Range(,)) =
    }

    SubShader
    {
        Pass
        {
            Tags
            {
                "LightMode" = "ForwardBase"
            }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fwdbase

            #include "UnityCg.cginc"
            #include "Lighting.cginc"
            #include "AutoLight.cginc"

            sampler2D _MainTex;
            fixed4 _Specular;
            float _Gloss;

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float3 normal : NORMAL;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv : TEXCOORD0;
                float3 worldNormal : TEXCOORD1;
                float4 worldPos: TEXCOORD2;
                SHADOW_COORDS()
            };

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex);
                TRANSFER_SHADOW(o);
                return o;
            }

            fixed4 frag(v2f i) : SV_TARGET
            {
                fixed4 albedo = tex2D(_MainTex, i.uv);
                fixed4 ambient = albedo * UNITY_LIGHTMODEL_AMBIENT;

                float3 worldLight = normalize(UnityWorldSpaceLightDir(i.worldPos.xyz));
                float3 worldView = normalize(UnityWorldSpaceViewDir(i.worldPos.xyz));
                fixed4 diff = albedo * _LightColor0 * max(, dot(i.worldNormal, worldLight));

                float3 halfDir = normalize(worldView + worldLight);
                fixed4 spec = albedo * _Specular * pow(max(, dot(halfDir, i.worldNormal)), _Gloss);

                UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos.xyz);

                fixed4 col = ambient + (diff + spec) * atten;
                return col;
            }

            ENDCG
        }

        Pass
        {
            Tags
            {
                "LightMode" = "ForwardAdd"
            }
            Blend One One

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fwdadd_fullshadows        // 添加阴影效果

            #include "UnityCg.cginc"
            #include "Lighting.cginc"
            #include "AutoLight.cginc"

            sampler2D _MainTex;
            fixed4 _Specular;
            float _Gloss;

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float3 normal : NORMAL;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv : TEXCOORD0;
                float3 worldNormal : TEXCOORD1;
                float4 worldPos: TEXCOORD2;
                SHADOW_COORDS()
            };

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex);
                TRANSFER_SHADOW(o);
                return o;
            }

            fixed4 frag(v2f i) : SV_TARGET
            {
                fixed4 albedo = tex2D(_MainTex, i.uv);

                float3 worldLight = normalize(UnityWorldSpaceLightDir(i.worldPos.xyz));
                float3 worldView = normalize(UnityWorldSpaceViewDir(i.worldPos.xyz));
                fixed4 diff = albedo * _LightColor0 * max(, dot(i.worldNormal, worldLight));

                float3 halfDir = normalize(worldView + worldLight);
                fixed4 spec = albedo * _Specular * pow(max(, dot(halfDir, i.worldNormal)), _Gloss);

                UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos.xyz);

                fixed4 col = (diff + spec) * atten;
                return col;
            }

            ENDCG
        }
    }

    Fallback "VertexLit"
}

效果如下：