Vertex中实现每顶点光照的镜面高光效果

Shader "JiKi/VertexLighting_Specular" 
{
    Properties
    {
        _Color("Base RGB",Color)=(1,1,1,1)
        _Shininess("Shininess",Range(0.001,10))=10
        _SpecColor("Specular Color",Color)=(1,1,1,1)
    }
    SubShader
    {
        Pass
        {
            Tags
            {
                "LightMode"="ForwardBase"
            }
        
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            
            uniform float4 _LightColor0;
            
            uniform float4 _Color;
            uniform float _Shininess;
            uniform float4 _SpecColor;
            
            struct inputVertex
            {
                float4 vertex:POSITION;
                float3 normal:NORMAL;
            };
            struct outPutVertex
            {
                float4 pos:SV_POSITION;
                float4 col:COLOR;    
            };
            
            outPutVertex vert(inputVertex input)
            {
                outPutVertex o;
                //工具函数
                float4x4 modelMatrix=_Object2World;
                float4x4 modelMatrixVerse=_World2Object;
                //世界空间中的法线向量
                float3 normalDir=normalize(mul(float4(input.normal,0.0),modelMatrixVerse).xyz);
                //视线方向
                float3 viewDir=normalize(_WorldSpaceCameraPos-mul(modelMatrix,input.vertex).xyz);
                //灯光
                float3 lightDir;
                float attenuation;//衰减量
                
                if(_WorldSpaceLightPos0.w==0)//证明是无限长度的方向向量
                {
                    attenuation=1.0;
                    lightDir=normalize(_WorldSpaceLightPos0).xyz;
                }
                else
                {
                    float3 vertexToLightSource=(_WorldSpaceLightPos0-mul(modelMatrix,input.vertex)).xyz;
                    float dist=length(vertexToLightSource);
                    lightDir=normalize(vertexToLightSource);
                    attenuation=1/dist;
                }
                //环境光
                float3 ambientColor=UNITY_LIGHTMODEL_AMBIENT.rgb*_Color.rgb;
                //漫反射
                float3 diffuseColor=attenuation*_LightColor0.rgb*_Color.rgb*max(0,dot(normalDir,lightDir));
                //镜面高光
                float3 specularColor;
                if(dot(lightDir,normalDir)<0)//证明是背面
                {
                    specularColor=float3(0,0,0);
                }
                else
                {
                    specularColor=attenuation*_LightColor0.rgb*_SpecColor.rgb*pow((max(0,dot(viewDir,reflect(-lightDir,normalDir)))),_Shininess);
                }
                //混合
                o.col=float4(ambientColor+diffuseColor+specularColor,1.0);
                o.pos=mul(UNITY_MATRIX_MVP,input.vertex);
                return o;
            }
            
            float4 frag(outPutVertex input):COLOR
            {
                return input.col;
            }
            ENDCG
        }
    }
}