1. Unity内部的ShadowCasterShader

Pass
{
    Name "ShadowCaster"
    Tags { "LightMode"="ShadowCaster" }

    CGPROGRAM
    #pragma vertex vert
    #pragma fragment frag
    #pragma multi_compile_shadowcaster
    #include "UnityCG.cginc"

    struct v2f
    {
        V2F_SHADOW_CASTER;
    };

    v2f vert(appdata_base v)
    {
        v2f o;
        TRANSFER_SHADOW_CASTER_NORMALOFFSET(o)
        return o;
    }

    float4 frag(v2f i) : SV_Target
    {
        SHADOW_CASTER_FRAGMENT(i)
    }
    ENDCG
}

2. ShadowRecv

• 在ForwardRendering.shader中添加SHADOW_COORDS TRANSFER_SHADOW SHADOW_ATTENUATION即可变成ShadowRecv.shader

  Shader "UnityShaderLearning/ShadowRecv"
  {
    Properties
    {
        _Diffuse("Diffuse", Color) = (1, 1, 1, 1)
        _Specular("Specular", Color) = (1, 1, 1, 1)
        _Gloss("Gloss", Range(8.0, 256)) = 20
    }
    SubShader
    {
        Pass
        {
            Tags { "LightMode"="ForwardBase" }
  
            CGPROGRAM
            #pragma multi_compile_fwbase
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"
            #include "AutoLight.cginc"
  
            fixed4 _Diffuse;
            fixed4 _Specular;
            float _Gloss;
  
            struct a2v
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };
  
            struct v2f
            {
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
                SHADOW_COORDS(2)
            };
  
            v2f vert(a2v v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldNormal = normalize(mul(v.normal, (float3x3)_World2Object));
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                TRANSFER_SHADOW(o);
                return o;
            }
  
            fixed4 frag(v2f i) :SV_Target
            {
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLightDir));
  
                fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
                fixed3 halfDir = normalize(viewDir + worldLightDir);
                fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(saturate(dot(worldNormal, halfDir)), _Gloss);
  
                fixed atten = 1.0;
                fixed4 shadow = SHADOW_ATTENUATION(i);
                return fixed4(ambient + (diffuse + specular) * atten * shadow, 1.0);
            }
  
            ENDCG
        }
        Pass
        {
            Tags { "LightMode"="ForwardAdd" }
  
            Blend SrcAlpha One
            CGPROGRAM
            #pragma multi_compile_fwbase
            #pragma vertex vert
            #pragma fragment frag
  
            #include "Lighting.cginc"
            #include "AutoLight.cginc"
  
            fixed4 _Diffuse;
            fixed4 _Specular;
            float _Gloss;
  
            struct a2v
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };
  
            struct v2f
            {
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
            };
  
            v2f vert(a2v v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                return o;
            }
  
            fixed4 frag(v2f i) : SV_Target
            {
                fixed3 worldNormal = normalize(i.worldNormal);
                #ifdef USING_DIRECTIONAL_LIGHT
                    fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);
                #else
                    fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz - i.worldPos.xyz);
                #endif
  
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * max(0, dot(worldNormal, worldLightDir));
  
                fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
                fixed3 halfDir = normalize(worldLightDir + viewDir);
                fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0, dot(worldNormal, halfDir)), _Gloss);
  
                #ifdef USING_DIRECTIONAL_LIGHT
                    fixed atten = 1.0;
                #else
                    #if defined (POINT)
                        float3 lightCoord = mul(_LightMatrix0, float4(i.worldPos, 1)).xyz;
                        fixed atten = tex2D(_LightTexture0, dot(lightCoord, lightCoord).rr).UNITY_ATTEN_CHANNEL;
                    #elif defined (SPOT)
                        float4 lightCoord = mul(_LightMatrix0, float4(i.worldPos, 1));
                        fixed atten = (lightCoord.z > 0) * tex2D(_LightTexture0, lightCoord.xy / lightCoord.w + 0.5).w * tex2D(_LightTextureB0, dot(lightCoord, lightCoord).rr).UNITY_ATTEN_CHANNEL;
                    #else
                        fixed atten = 1.0;
                    #endif
                #endif
  
                return fixed4((diffuse + specular) * atten, 1.0);
            }
            ENDCG
        }
    }
    FallBack "Specular"
  }
  

3. 透明物体的阴影效果

Shader "UnityShaderLearning/AlphaTestWithShadow"
{
    Properties
    {
        _Color ("Main Tint", Color) = (1, 1, 1, 1)
        _MainTex ("Main Tex", 2D) = "white"{}
        _Cutoff ("Alpha Cutoff", Range(0, 1)) = 0.55
    }
    SubShader
    {
        Tags { "Queue"="AlphaTest" "IgnoreProjector" = "True" "RenderType"="TransparentCutout"}

        Pass
        {
            Tags { "LightMode"="ForwardBase" }
            Cull Off
            CGPROGRAM

            #pragma multi_compile_fwdbase
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"
            #include "AutoLight.cginc"

            fixed4 _Color;
            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed _Cutoff;

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

            struct v2f
            {
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
                float2 uv : TEXCOORD2;
                SHADOW_COORDS(3)
            };

            v2f vert(a2v v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
                TRANSFER_SHADOW(o);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
                fixed4 texColor = tex2D(_MainTex, i.uv);
                clip (texColor.a - _Cutoff);

                fixed3 albedo = texColor.rgb * _Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldNormal, worldLightDir));
                UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);
                return fixed4(ambient + diffuse * atten, 1.0);
            }
            ENDCG
        }
    }
    FallBack "VertexLit"
}