主角场景Shader效果：描边

基本思路：Shader用两个Pass，一个渲染描边部分，一个渲染物体部分。

Pass1：剔除正面，渲染背面，把顶点延法线方向外围扩展一定宽度，用来表现描边的粗细，这部分用自己设定的颜色。

Pass2：剔除背面，渲染正面，正常渲染所看到的物体模型。

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

 Shader "xj/ModelEffect/Outline" {
     Properties {
         _Color ("模型颜色", Color) = (,,,)
         _OutlineColor ("描边颜色", Color) = (,,,)
         _Outline ("描边宽度", float) = 0.03
         _MainTex ("模型贴图", 2D) = "white" {}
         _AlphaTex ("Alpha (A)", 2D) = "white" {}
         _intensity ("强度", float ) = 1.0
     }

     CGINCLUDE
         #include "UnityCG.cginc"

         struct appdata {
             float4 vertex : POSITION;
             float3 normal : NORMAL;
             half2 texcoord : TEXCOORD0;
         };

         struct v2f {
             float4 pos : SV_POSITION;
             fixed4 color : COLOR;
             half2 texcoord : TEXCOORD0;
         };

         struct basevt {
             float4 pos : SV_POSITION;
             half2 texcoord : TEXCOORD0;
         };

         sampler2D _MainTex;
         sampler2D _AlphaTex;
         uniform fixed _Outline;
         uniform fixed4 _OutlineColor;
         uniform fixed4 _Color;
         fixed _intensity;

         v2f outline_vert(appdata v)
         {
             //在vertex阶段，每个顶点按照法线的方向偏移一部分，不过这种会造成近大远小的透视问题
             //正确的做法是转换到投影空间下做偏移
             //v.vertex.xyz += v.normal * _Outline;

             v2f o;
             o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
             float3 norm = mul ((float3x3)UNITY_MATRIX_IT_MV, v.normal);
             float2 offset = TransformViewToProjection(norm.xy);
             o.pos.xy += offset * _Outline;
             o.color = _OutlineColor;
             o.texcoord = v.texcoord;
             return o;
         }

         fixed4 outline_frag(v2f i): SV_Target
         {
             fixed4 color = i.color;
             color.a = tex2D(_AlphaTex, i.texcoord).a;
             return color;
         }

         basevt base_vert(appdata v)
         {
             basevt o;
             o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
             o.texcoord = v.texcoord;
             return o;
         }

         fixed4 base_frag(basevt i): SV_Target
         {
             fixed4 col = tex2D(_MainTex, i.texcoord) * _Color * _intensity;
             col.a = tex2D(_AlphaTex, i.texcoord).a * _Color.a;
             return col;
         }
     ENDCG

     SubShader {
         Tags { "Queue" = "Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
         Fog {Mode Off}

         Pass
         {
             Name "OUTLINE"
             Cull Front //剔除正面
             CGPROGRAM

             #pragma vertex outline_vert
             #pragma fragment outline_frag
             #pragma fragmentoption ARB_precision_hint_fastest

             ENDCG
         }

         Pass
         {
             Name "BASE"
             Cull Back //剔除背面
             CGPROGRAM

             #pragma vertex base_vert
             #pragma fragment base_frag
             #pragma fragmentoption ARB_precision_hint_fastest

             ENDCG
         }
     }
     FallBack "xj/Default"
 }