双面渲染的透明效果

透明度测试的双面渲染透明效果

因为透明度测试没有关深度写入，所以这个透明物体的像素级别的深度信息都是排序正确的，所以直接使用Cull指令即可

        Pass
        {
            Tags{"LightModel"="ForwardBase"}
            Cull Off
        }

透明度混合的双面渲染透明效果

透明度混合关闭了深度写入，所有这个透明物体没有正确的先后顺序，而渲染透明效果的很重要的一点就是：一定要保证图元是从后往前渲染，所以如果直接关掉剔除功能，是得不到正确的前后面的。所以使用两个Pass来渲染，第一个只渲染背面，第二个值渲染正面，由于Pass是按顺序执行的，所有我们的背面总在正面之前渲染，所以能得到正确的渲染关系。

Shader "Unlit/AlphaBlend"
{
    Properties
    {
        _Color("Color Tint",Color)=(1,1,1,1)
        _MainTex("Main Tex",2D) = "white"{}
        _AlphaScale("Alpha Scale",Range(0,1))=1
    }

    SubShader
    {
        Tags{"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}

        Pass
        {
            Tags{"LightModel"="ForwardBase"}

            Cull Front //先渲染背面
            ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            CGPROGRAM
            #include "Lighting.cginc"
            #pragma vertex vert
            #pragma fragment frag

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

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

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


            v2f vert(a2v v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;
                o.worldNormal = UnityObjectToWorldNormal(v.normal);

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

                return o;
            }

            fixed4 frag(v2f i):SV_TARGET
            {
                float3 wordNormal = normalize(i.worldNormal);
                float3 worldLightDir = UnityWorldSpaceLightDir(i.worldPos);

                fixed4 texColor = tex2D(_MainTex,i.uv);
                fixed3 albedo = texColor.rgb*_Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT * albedo;
                fixed3 diffuse = _LightColor0.rgb * albedo * saturate(dot(wordNormal,worldLightDir));

                return fixed4(ambient+diffuse,texColor.a*_AlphaScale);
            }

            ENDCG
        }

        Pass
        {
            Tags{"LightModel"="ForwardBase"}

            Cull Back  //在渲染正面
            ZWrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            CGPROGRAM
            #include "Lighting.cginc"
            #pragma vertex vert
            #pragma fragment frag

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

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

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


            v2f vert(a2v v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;
                o.worldNormal = UnityObjectToWorldNormal(v.normal);

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

                return o;
            }

            fixed4 frag(v2f i):SV_TARGET
            {
                float3 wordNormal = normalize(i.worldNormal);
                float3 worldLightDir = UnityWorldSpaceLightDir(i.worldPos);

                fixed4 texColor = tex2D(_MainTex,i.uv);
                fixed3 albedo = texColor.rgb*_Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT * albedo;
                fixed3 diffuse = _LightColor0.rgb * albedo * saturate(dot(wordNormal,worldLightDir));

                return fixed4(ambient+diffuse,texColor.a*_AlphaScale);
            }

            ENDCG
        }
    }

    Fallback "Transparent/VertexLit"
}