Shader理論《五》漫反射光照模型

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漫反射的光照模型計算公式 ：

由上公式可知計算漫反射我們要知道四個參數：入射光線的顏色跟強度C_light,材質的漫反射係數M_diffuse,表面法線方向l。

1.逐頂點光照漫反射，背光面與向光面交界處有鋸齒

Shader "a幻世界/DiffuseVertex"
{
	Properties{
		_Diffuse("Diffuse",Color) = (1,1,1,1)
	}
	SubShader{
		Pass{
		Tags {"LightMode" = "ForwardBase"}
		CGPROGRAM
		#pragma vertex vert
		#pragma fragment frag
		#include "Lighting.cginc"
		fixed4 _Diffuse;
		struct a2v {
				float4 vertex : POSITION;//獲取頂點信息
				float3 normal : NORMAL;//獲取法線信息
			};

			struct v2f {
				float4 pos : SV_POSITION;//賦值頂點信息
				fixed3 color : COLOR;//賦值顏色信息
			};
	    v2f vert(a2v v) {
		v2f o;
		o.pos = UnityObjectToClipPos(v.vertex);//把模型空間的頂點轉換到裁剪空間，內置模型世界投影矩陣
		fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;//使用內置變量獲取環境光
		fixed3 worldNormal = normalize(mul(v.normal, (float3x3)unity_WorldToObject));//獲取光源的顏色跟強度
		fixed3 worldLight = normalize(_WorldSpaceLightPos0.xyz);//獲取光源的方向
		fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLight));
		o.color = ambient + diffuse;
		return o;
	}
	fixed4 frag(v2f i) : SV_Target{
				return fixed4(i.color, 1.0);
	}
		ENDCG
	}

	}
    FallBack "Diffuse"
}

2.逐像素光照，光照無法到達的區域模型是全黑的，沒有明暗變化

Shader "a幻世界/DiffusePixel"
{
	Properties
	{
	   _Diffuse("Deffuse",Color) = (1,1,1,1)
	}
		SubShader{
		Pass{
			Tags {"LightMode" = "ForwardBase"}
			CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag
	#include "Lighting.cginc"
			fixed4 _Diffuse;
	struct a2v {
		float4 vertex:POSITION;
		float3 normal:NORMAL;
	};
	struct v2f {
		float4 pos:SV_POSITION;
		fixed3 worldNormal : COLOR;
	};
	v2f vert(a2v v){
	v2f o;
	o.pos = UnityObjectToClipPos(v.vertex);
	o.worldNormal = mul(v.normal,(float3x3)unity_WorldToObject);
	return o;
	}

	fixed4 frag(v2f i):SV_Target{
		fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
	fixed3 worldNormal = normalize(i.worldNormal);
	fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);
	fixed3 diffuse = _LightColor0.rgb*_Diffuse.rgb*saturate(dot(worldNormal, worldLightDir));
	fixed3 color = ambient + diffuse;
	return fixed4(color,1);
	}
		ENDCG
}
	}
   
    FallBack "Diffuse"
}

3.半蘭伯特光照模型

Shader "a幻世界/HalfLambert"
{
	Properties
	{
	   _Diffuse("Deffuse",Color) = (1,1,1,1)
	}
		SubShader{
		Pass{
			Tags {"LightMode" = "ForwardBase"}
			CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag
	#include "Lighting.cginc"
	fixed4 _Diffuse;
	struct a2v {
		float4 vertex:POSITION;
		float3 normal:NORMAL;
	};
	struct v2f {
		float4 pos:SV_POSITION;
		fixed3 worldNormal : COLOR;
	};
	v2f vert(a2v v) {
	v2f o;
	o.pos = UnityObjectToClipPos(v.vertex);
	o.worldNormal = mul(v.normal,(float3x3)unity_WorldToObject);
	return o;
	}

	fixed4 frag(v2f i) :SV_Target{
		fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
	fixed3 worldNormal = normalize(i.worldNormal);
	fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);
	fixed3 halfLambert = dot(worldNormal,worldLightDir)*0.5+0.5;
	fixed3 diffuse = _LightColor0.rgb*_Diffuse.rgb*halfLambert;
	fixed3 color = ambient + diffuse;
	return fixed4(color,1);
	}
		ENDCG
}
	}
    FallBack "Diffuse"
}

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