add an outline for model in unity3d

outline.shader

    Shader "Outline" {  
        Properties {  
            _Color ("Main Color", Color) = (.5,.5,.5,1)  
            _OutlineColor ("Outline Color", Color) = (0,0,0,1)  
            _Outline ("Outline width", Range (0.0, 0.03)) = .005  
            _MainTex ("Base (RGB)", 2D) = "white" { }  
        }  
        CGINCLUDE  
            #include "UnityCG.cginc"  
            struct appdata {  
                float4 vertex : POSITION;  
                float3 normal : NORMAL;  
            };  
            struct v2f {  
                float4 pos : POSITION;  
                float4 color : COLOR;  
            };  
            uniform float _Outline;  
            uniform float4 _OutlineColor;  
            v2f vert(appdata v) {  
                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 * o.pos.z * _Outline;  
                o.color = _OutlineColor;  
                return o;  
            }  
        ENDCG  
        SubShader {  
            Tags { "Queue" = "Transparent" }  
            Pass {  
                Tags { "LightMode" = "Always" }  
                Cull Off  
                ZWrite Off  
                //ZTest Always//始终通过深度测试，即可以渲染  
                //ColorMask RGB // alpha not used  
                Blend SrcAlpha OneMinusSrcAlpha // Normal  
      
                CGPROGRAM  
                #pragma vertex vert  
                #pragma fragment frag  
                half4 frag(v2f i) :COLOR {  
                    return i.color;  
                }  
                ENDCG  
            }  
            Pass {  
				Cull Off
                Name "BASE"  
                ZWrite On  
                ZTest LEqual  
                Blend SrcAlpha OneMinusSrcAlpha  
                Material {  
                    //Diffuse [_Color]  
                    //Ambient [_Color]  
                }  
                Lighting On  
                
                SetTexture [_MainTex] {  
                    //Combine previous * primary DOUBLE  
                }  
            }  
        }  
        Fallback "Diffuse"  
    }