Shader法线贴图

法线贴图,在切线空间下计算（Cubemap环境映射不可以用，要用世界空间下计算） 参考 《unity shader 入门精要》

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

Shader "Book/07.TangentNormal"
{
//法线贴图
    Properties
    {
        _Color ("Color Tint",Color)=(1,1,1,1)
        _MainTex ("Main Tex", 2D) = "white" {}
        _BumpMap("Normal Map",2D) = "white" {}
        _BumpScale("Bump Scale",Float) = 1.0
        _Specular("Specular",Color) = (1,1,1,1)
        _Gloss("Gloss",Range(8.0,256)) = 20
    }
    SubShader
    {

        Pass
        {
            Tags { "LightMode"="ForwardBase" }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            //#pragma multi_compile_fog

            #include "UnityCG.cginc"
            #include "Lighting.cginc"


            float4 _Color,_Specular;
            sampler2D _MainTex;
            sampler2D _BumpMap;
            float _BumpScale,_Gloss;

            float4 _MainTex_ST;
            float4 _BumpMap_ST;



            struct a2v
            {
                float4 vertex : POSITION;
                float3 normal: NORMAL;
                float4 tangent:TANGENT;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
                float4 uv : TEXCOORD0;
                float3 lightDir:TEXCOORD1;
                float3 viewDir:TEXCOORD2;
            };


            v2f vert (a2v v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv.xy = v.texcoord.xy*_MainTex_ST.xy + _MainTex_ST.zw;
                o.uv.zw = v.texcoord.xy*_BumpMap_ST.xy + _BumpMap_ST.zw;

                float3 binormal = cross(v.normal,v.tangent.xyz)*v.tangent.w;
                float3x3 rotation = float3x3(v.tangent.xyz,binormal,v.normal);

                //TANGENT_SPACE_ROTATION;

                //将光源位置减去顶点位置，这样就得到光照方向了 — 但是我们应该首先将顶点位置乘上光源的w分量，如果是平行光，w分量为0，得到的结果为0，说明顶点位置全变为(0.0, 0.0, 0.0)了，这样光照方向就是光源本身的位置（return objSpaceLightPos.xyz）。对于点光源，w为1，所以乘上顶点位置后，顶点位置无变化，这样计算的光照方向就是（return objSpaceLightPos.xyz – v.xyz）。
                float3 lightDir = mul(unity_WorldToObject,_WorldSpaceLightPos0).xyz - v.vertex*_WorldSpaceLightPos0.w;
                o.lightDir = mul(rotation,lightDir);

                float3 viewDir = mul(unity_WorldToObject,float4(_WorldSpaceCameraPos,1)).xyz-v.vertex.xyz;
                o.viewDir = mul(rotation,viewDir);

                o.viewDir = normalize(o.viewDir);
                o.lightDir = normalize(o.lightDir);

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                i.viewDir = normalize(i.viewDir);
                i.lightDir = normalize(i.lightDir);

                //uppack  normal
                fixed3 tangentNormal; 
                fixed4 packedNormal  = tex2D(_BumpMap,i.uv.zw);
                #if defined(UNITY_NO_DXT5nm)
                    tangentNormal.xyz = packedNormal.xyz*2 -1;
                #else
                    // --rgba  -- xyzw 
                    //DXTnm 格式中a通道（即w分量）对应发现x分量,g通道（即y分量）对应发现y分量,
                    //tangentNormal.xy = packedNormal.ag*2 -1;
                    tangentNormal.xy = packedNormal.wy*2 -1;
                    tangentNormal=tangentNormal* _BumpScale;
                    tangentNormal.z = sqrt(1.0-max(0,dot(tangentNormal.xy,tangentNormal.xy)));
                #endif


                fixed3 albedo = tex2D(_MainTex,i.uv).rgb*_Color.rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz*albedo;
                fixed3 diffuse = _LightColor0.rgb*albedo*max(0,dot(tangentNormal,i.lightDir));
                fixed3 halfDir = normalize(i.lightDir+i.viewDir);
                fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(max(0,dot(tangentNormal,halfDir)),_Gloss);


                return fixed4(ambient+diffuse+specular,1.0);
            }
            ENDCG
        }
    }
    FallBack "Specular"
}