unity 遮罩纹理

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遮罩纹理

通过采样得到纹理的纹理像素值，然后使用其中某个或者某几个通道的值来与某种表面属性进行相乘，这样当该通道的值为0时，可以保护表面不受该属性的影响。

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Shader "My/Mask"{
    properties{
     	_Color("Color", Color)           	= (1,1,1,1)
        _MainTex("MainTex", 2D)          	= "white"{}
        _BumpMap("Normal Map", 2D)       	= "bump" {}
        _BumpScale("Bump Scale", Float)  	= 1.0
		_Specular("Specular", Color)     	= (1,1,1,1)
        _SpecularScale("Specular Scale", Float) = 1.0
        _SpecularMask("Specular Mask", 2D)  = "white" {}
        _Gloss("Gloss", Range(8.0, 256)) = 20
    }
    
    SubShader{
        Pass{
            Tags{"LightMode"="ForwardBase"}
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"
            fixed4 _Color;
            sampler2D _MainTex;
            float4 _MainTex_ST;
            sampler2D _BumpMap;
            sampler2D _SpecularMask;
            float _SpecularScale;
            fixed4 _Specular;
            float _Gloss;
            
            struct a2v{
                float4 vertex 		: POSITION;
                float3 normal		: NORMAL;
                float4 tangent      : TANGENT;
                float4 texcoord		: TEXCOORD0;
            };
            
            struct v2f{
                float4 pos 		: SV_POSITION;
                float2 uv	    : TEXCOORD0;
                float3 lightDir : TEXCOORD1;
                float3 viewDir  : TEXCOORD2;
            };
            
            v2f vert(a2v v){
                v2f o;
                o.pos 		= mul(UNITY_MATRIX_MVP, v.vertex);
                o.uv.xy		= v.texcoord.xy * _MainTex_ST.xy + _MainTex_ST.zw;
                TANGENT_SPACE_ROTATION;
                o.lightDir = mul(rotation, ObjSpaceLightDir(v.vertex)).xyz;
                o.viewDir  = mul(rotation, ObjSpaceViewDir(v.vertex)).xyz;
                return o;
            }
            
            fixed4 frag(v2f i) : SV_Target{
                fixed3 tangentLightDir = normalize(i.lightDir);
                fixed3 tangentViewDir  = normalize(i.viewDir);
                fixed3 tangentNormal   = UnpackNormal(tex2D(_BumpMap, i.uv));
                tangentNormal.xy *= _BumpScale;
                tangentNormal.z = sqrt(1 - saturate(dot(tangentNormal.xy, tangentNormal.xy)));
                fixed3 albedo  = tex2D(_MainTex, i.uv).rgb  * _Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(tangentNormal, tangentLightDir));
                fixed3 halfDir = normalize(tangentLightDir + tangentViewDir);
                fixed  specularMask = tex2D(_SpecularMask, i.uv).r * _SpecularScale;
                fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0, dot(tangentNormal, halfDir)) ,_Gloss) * specularMask;
                return fixed4(ambient + diffuse + specular, 1.0);
            }
            
            ENDCG
        }
    }
}