第三章 （3）方式反射模型

                                              方式反射模型

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Unity 提供的 光照函數

光照函數類型	函數說明
非視線 依賴	half4 Lighting+Name(SurfaceOutput s, half3 lightDir, half atten);
視線 依賴	half4 Lighting+Name(SurfaceOutput s, half3 lightDir, half3 viewDir, half atten);

• SurfaceOutput :  表面函數 輸出結構體
• lightDir : 光線方向
• viewDir : 視口方向
• atten : 光線衰減 率 0-1

Phong Specular 方式反射模型

Shader "Custom/chapter03/PhongSpecular"
{
    Properties
    {
        _MianTint ("Diffuse Tint", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
 
		_SpecularColor("Specular Color",Color) = (1,1,1,1)
		_SpecPower("Specular Power",Range(0.1,30)) = 1
	}
		SubShader
		{
			Tags { "RenderType" = "Opaque" }
			LOD 200

			CGPROGRAM
			// Physically based Standard lighting model, and enable shadows on all light types
			#pragma surface surf CustomPhong  

			// Use shader model 3.0 target, to get nicer looking lighting
			#pragma target 3.0

			float4 _MianTint;
			sampler2D _MainTex;
			float4 _SpecularColor;
			float _SpecPower;

        struct Input
        {
            float2 uv_MainTex;
        };


        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
            // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutput o)
        {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _MianTint;
            o.Albedo = c.rgb;
            o.Alpha = c.a;
        }

		///  參數一  表面函數輸出結構體
		///  參數二  光線方向
		///  參數三  視口方向
		///  參數四  光線衰減 率 0-1

		fixed4 LightingCustomPhong(SurfaceOutput s, fixed3 lightDir, half3 viewDir, fixed atten)
		{
			// 反射
			float NdotL = dot(s.Normal, lightDir);
			float3 refVector = normalize(2.0 * s.Normal * NdotL - lightDir);
			// 鏡面反射
			float Spec = pow(max(0, dot(refVector, viewDir)), _SpecPower);
			float3 finalSpec = _SpecularColor.rgb * Spec;

			//Final Effect
			fixed4 c;
			c.rgb = (s.Albedo * _LightColor0.rgb * max(0, NdotL)*atten) + (_LightColor0.rgb*finalSpec);
			c.a = s.Alpha;
			return c;

		}
        ENDCG
    }
    FallBack "Diffuse"
}