Unity 复杂模型如何改变透明度？

问题遇到的现象和发生背景

所用模型是人体肝脏器官，但是在改变其透明度时出现遮挡，不能通过人体在各个角度完整看到内部器官的问题

我的解答思路和尝试过的方法

在网上找了很多资料，试了采用两个pass以及双面渲染
两个pass渲染效果好些。如下：

    Properties
    {
          _Color("Main Tint", Color) = (1, 1, 1, 1)
        _MainTex("Main Tex", 2D) = "white" {}
        _AlphaScale("Alpha Scale", Range(0, 1)) = 1
    }
    Subshader
    {
        Tags{"Queue" = "Transparent" "IgnoreProjector" = "False" "RenderType" = "Transparent"}
        //第一个pass:计算深度，第二个pass:着色
        pass
        {
            ZWrite On
            ColorMask 0
        }

        pass
        {
            Tags { "LightMode" = "ForwardBase"}
            Zwrite Off
            Blend SrcAlpha OneMinusSrcAlpha

            CGPROGRAM

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

            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 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
                float2 uv : TEXCOORD2;
            };

            v2f vert(a2v v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);

                o.worldNormal = UnityObjectToWorldNormal(v.normal);

                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;

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

                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);

                fixed3 albedo = texColor.rgb * _Color.rgb;

                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;

                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldNormal, worldLightDir));

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

双面渲染会出现穿透现象，如下：

        Properties
        {
            _Color("Color Tint", Color) = (1,1,1,1)
            _MainTex("Texture", 2D) = "white" {}
            _AlphaScale("Alpha Scale", Range(0,1)) = 1
        }
        SubShader
        {
        Tags { "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Transparent" }
        Pass
        {
            Tags {"LightMode" = "ForwardBase"}
            Cull Front
            ZWrite off
            Blend SrcAlpha OneMinusSrcAlpha
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Lighting.cginc"

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

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

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

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                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);

                fixed3 albedo = texColor.rgb * _Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;

                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldLightDir, worldNormal));

                return fixed4(ambient + diffuse, texColor.a * _AlphaScale);
            }
            ENDCG
        }
            Pass
        {
            Tags {"LightMode" = "ForwardBase"}
            Cull Back
            ZWrite off
            Blend SrcAlpha OneMinusSrcAlpha
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Lighting.cginc"

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

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

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

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                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);

                fixed3 albedo = texColor.rgb * _Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;

                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldLightDir, worldNormal));

                return fixed4(ambient + diffuse, texColor.a * _AlphaScale);
            }
            ENDCG
        }
    }
        Fallback "Transparent/VertexLit"

我想要达到的结果

复杂模型可以改变透明度，不会出现遮挡问题

已实现此效果

方法教程

推荐使用插件OIT
如下图：

使用方法：
将插件自带代码给相机，并做如下设置，也可以根据自己项目调整

然后把OIT插件里的材质球OIT赋给需要改变透明度的物体

齐活！

如果两个pass的方法可以实现你的目的
那你还有什么问题