渐变纹理7.3

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

//7.3渐变纹理
Shader "Unlit/Chapter7-RampTexture"
{
	Properties{
		_Color("Color Tint",Color) = (1,1,1,1)
		_RampTex("Ramp Tex",2D)="white"{}
		_Specular("Specular",Color)=(1,1,1,1)
		_Gloss("Gloss",Range(8.0,256))=20
	}
	SubShader{
		pass {
			Tags{"LighitMode" = "ForwardBase"}
		CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include"Lighting.cginc"

				fixed4 _Color;
			sampler2D _RampTex;
			float4 _RampTex_ST;
			fixed4 _Specular;
			float _Gloss;

			struct a2v{
			float4 vertex : POSITION;
			float3 normal : NORMAL;
			float4 texcoord:TEXCOORD0;
			};
			
			struct v2f{
			float4 pos:SV_POSITION;
			float3 worldNormal:TEXCOORD0;
			float3 worldPos:TEXCOORD1;
			float2 uv:TEXCOORD2;
			};

			v2f vert(a2v v) {
				v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
				o.uv = TRANSFORM_TEX(v.texcoord, _RampTex);
				return o;
			}
			
			fixed4 frag(v2f i):SV_Target {
			//计算世界空间下的法线方向
			fixed3 worldNormal = normalize(i.worldNormal);
			//计算世界空间下的光照方向
			fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
			//得到环境光部分
			fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;

			//use the texture to sample the diffuse color
			//半兰伯特光照
			fixed halfLambert = 0.5*dot(worldNormal, worldLightDir) + 0.5;
			//计算得到漫反射颜色
			/*使用 halfLambert 构建一个纹理坐标，并用这个纹理坐标对渐变纹理 _RampTex进行采样
			(_RamTex实际是一个一维纹理，它在纵轴方向上颜色不变)
			因此纹理的U和V方向我们都使用了halfLambert，
			然后，把从渐变纹理采样得到的颜色和材质颜色_Color相乘，得到最终的漫反射颜色
			*/
			fixed3 diffuseColor = tex2D(_RampTex, fixed2(halfLambert, halfLambert)).rgb*_Color.rgb;
			
			//计算漫反射光的结果
			fixed3 diffuse = _LightColor0.rgb*diffuseColor;
			
			//获得世界空间中的观察方向
			fixed3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
			//Bill-Phong光照模式
			fixed3 halfDir = normalize(worldLightDir + viewDir);
			//计算高光反射项
			fixed3 specular = _LightColor0.rgb*_Specular.rgb*_Specular.rgb*pow(max(0, dot(worldNormal, halfDir)), _Gloss);

			return fixed4(ambient + diffuse + specular, 1.0);

			}
		ENDCG
		}

	}

			Fallback"Specular"
}