带法线贴图的高光着色

//blinn高光 带法线细节
//思路:使用切线空间下面的法线贴图(效率虽然低点,但是通用性好)
//顶点函数计算切线空间转世界空间矩阵
//片元函数采样法线贴图 并且反隐射 再计算光照
Shader "Tang/617/BlinnTexNormal"{
	Properties{
		_Color("Tin Color",Color) = (1,1,1,1)
		_MainTex("漫反射贴图",2D) = "white" { }
		_BumpTex("法线贴图",2D) = "bump" { }
		_BumpScale("BumpScale",Range(1,8)) = 2
		_Specular("Specular",Color) = (1,1,1,1)
		_Gloss("Gloss",Range(1,64)) = 8
	}

	SubShader{
		Pass{
			Tags {"LightMode" = "ForwardBase"}
			CGPROGRAM
			#pragma vertex vert 
			#pragma fragment frag 
			#include "Lighting.cginc"

			struct a2v{
				float4 vertex:POSITION;
				float3 normal:NORMAL;
				float4 tangent:TANGENT;
				float4 texcoord:TEXCOORD0;
			};
			struct v2f{
				float4 pos:SV_POSITION;
				float4 uv:TEXCOORD0;
				//切线空间转世界空间矩阵
				float4 TtoW0:TEXCOORD1;
				float4 TtoW1:TEXCOORD2;
				float4 TtoW2:TEXCOORD3;
			};

			fixed4 _Color;
			fixed4 _Specular;
			fixed _Gloss;
			sampler2D _MainTex;float4 _MainTex_ST;
			sampler2D _BumpTex;float4 _BumpTex_ST;
			fixed _BumpScale;

			v2f vert(a2v v){
                v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
				fixed3 worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;
				fixed3 worldTangent = UnityObjectToWorldDir(v.tangent.xyz);
				fixed3 worldBinormal = cross(worldNormal,worldTangent)*v.tangent.w;//保证副法线的方向正确*v.tangent.w？
				//uv
				o.uv.xy = TRANSFORM_TEX(v.texcoord,_MainTex);
				o.uv.zw = TRANSFORM_TEX(v.texcoord,_BumpTex);
				//切线到世界空间的矩阵
				o.TtoW0 = float4(worldTangent.x,worldBinormal.x,worldNormal.x,worldPos.x);
				o.TtoW1 = float4(worldTangent.y,worldBinormal.y,worldNormal.y,worldPos.y);
				o.TtoW2 = float4(worldTangent.z,worldBinormal.z,worldNormal.z,worldPos.z);

				return o;
			}

			fixed4 frag(v2f i):SV_Target{
				//世界坐标
				fixed3 worldPos = fixed3(i.TtoW0.w,i.TtoW1.w,i.TtoW2.w);
				//世界光线方向
				fixed3 lightDir = UnityWorldSpaceLightDir(worldPos);
				//世界观察方向
				fixed3 viewDir = UnityWorldSpaceViewDir(worldPos);
				//采样法线贴图 并反隐射到-1,1(像素只能是0-1 所以需要反隐射)
				fixed3 bump = UnpackNormal(tex2D(_BumpTex,i.uv.zw));
				bump.xy *= _BumpScale;
				bump.z = sqrt(1-saturate(dot(bump.xy,bump.xy)));
				bump = normalize(half3(dot(i.TtoW0.xyz,bump),dot(i.TtoW1.xyz,bump),dot(i.TtoW2.xyz,bump)));
				//下面使用法线进行光照计算
                fixed3 albedo = tex2D(_MainTex,i.uv.xy)*_Color.rgb;
				fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz*albedo;
				fixed3 diffuse = _LightColor0.rgb*albedo* saturate(dot(bump,lightDir));								
				//blinn
				fixed3 h = normalize(lightDir+viewDir);
				fixed3 specular = _LightColor0.rgb*_Specular.rgb* pow(saturate(dot(h,bump)),_Gloss);
				return fixed4(ambient+diffuse+specular,1);
			}

			ENDCG
		}
	}

	FallBack "Diffuse"
}