Record: Shader model formula and achieve illumination

The following comes from the basis of light <UnityShader Getting Started Essentials> Chapter VI of Unity

1. Diffuse formula
Lambert law: the angle between the light intensity of the reflected light and the surface normal direction is proportional to the cosine value
C _diffuse = (C _Light * M _diffuse ) * of saturate (DOT (n-, I))
C _Light : the color of the incident light intensity and
M _diffuse : albedo material
saturate (x): x, taken at the [0,1] in the range of
dot (x, y): x and y dot
n: a surface normal line
i: light source direction
to achieve:

Shader "Custom/Diffuse" {
Properties{
	_Diffuse("Color", Color) = (1,1,1,1)

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


		fixed4 _Diffuse;
		struct Input {
			float4 vertex:POSITION;
			float3 normal:Normal;
		};
		struct v2f {
			float4 pos:SV_POSITION;
			fixed3 color : COLOR;
		};
		
		v2f vert(Input i)
		{
			v2f o;
			//转换顶点坐标
			o.pos = mul(UNITY_MATRIX_MVP, i.vertex);
			//环境色
			fixed3 ambine = UNITY_LIGHTMODEL_AMBIENT.xyz;
			//法线
			fixed3 worldNormal = normalize(mul(i.normal, (float3x3)unity_WorldToObject));
			//入射光线
			fixed3 worldLight = normalize(-_WorldSpaceLightPos0.xyz);
			//漫反射公式
			fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLight));
			//最终颜色
			o.color = ambine + diffuse;
			return o;
		}

		fixed4 frag(v2f i):SV_Target
		{
			return fixed4(i.color,1.0);
		}
		ENDCG
	}
}
FallBack "Diffuse"
}

2. Semi-Lambert equation:
C _diffuse = (C _Light * M _diffuse ) (DOT S * (n-, I) + O)
C _Light : the color of the incident light intensity and
M _diffuse : albedo material
dot (x , y): x and y by point
n: surface normal
i: light source direction
S: scale factor, typically 0.5
O: shift coefficient, typically 0.5
to achieve:

	//在漫反射公式 实现代码中替换漫反射公式
	fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLight)*0.5+0.5);

3. Specular formula
C _Specular = (C _Light * M _Specular ) * of saturate (DOT (V, the reflect (I, n-))) ^GLOSS
C _Light : the color of the incident light and the intensity
M _Specular : specular reflection coefficient of the material
of saturate ( x): x, taken at the [0,1] in the range of
dot (x, y): x and y dot
v: viewing direction
i: illumination direction
n: normal direction
reflect (i, n): the I ( incident direction), and n (normal direction) direction of the retroreflection
gloss: gloss, the smaller the highlight.

Shader "Custom/Specular" {
	Properties{
		_Diffuse("Color", Color) = (1,1,1,1)
		_Specular("Specular",Color) = (1,1,1,1)
		_Gloss("Gloss",Range(1,10)) = 1
	}
	SubShader{
		Pass
		{
			Tags{ "RenderType" = "Opaque" }
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "Lighting.cginc"


			fixed4 _Diffuse;
			float _Gloss;
			fixed4 _Specular;
			struct Input {
				float4 vertex:POSITION;
				float3 normal:Normal;
			};
			struct v2f {
				float4 pos:SV_POSITION;
				fixed3 color : COLOR;
			};
			
			v2f vert(Input i)
			{
			v2f o;
				//转换顶点坐标
				o.pos = mul(UNITY_MATRIX_MVP, i.vertex);
				//环境色
				fixed3 ambine = UNITY_LIGHTMODEL_AMBIENT.xyz;
				//法线
				fixed3 worldNormal = normalize(mul(i.normal, (float3x3)unity_WorldToObject));
				//入射光线
				fixed3 worldLight = normalize(-_WorldSpaceLightPos0.xyz);
				//漫反射公式
				fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(0.5f * dot(worldNormal, worldLight)+0.5f);

				//反射方向 reflect(入射方向，法线)
				fixed3 reflectDir = normalize(reflect(worldLight, worldNormal));
				//视觉方向
				fixed3 viewDir = normalize(-_WorldSpaceCameraPos.xyz - mul(unity_ObjectToWorld, i.vertex).xyz);
				//高光公式
				fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(saturate(dot(reflectDir, viewDir)), _Gloss);

				//最终颜色
				o.color = ambine + diffuse + specular;
				return o;
			}
			fixed4 frag(v2f i):SV_Target
			{
				return fixed4(i.color,1.0);
			}
			ENDCG
		}
	}
	FallBack "Diffuse"
}

4.Blinn-Phong formula
C _Specular = (C _Light * M _Specular ) of saturate (DOT (n-, the normalize (I + V))) ^GLOSS
C _Light : the color of the incident light intensity and
M _Specular : specular reflection coefficient of the material
of saturate ( x): x, taken at the [0,1] in the range of
dot (x, y): x and y dot
v: viewing direction
i: illumination direction
normalize: normalized vector
gloss: gloss, greater highlights The smaller.
achieve:

//在高光反射公式中做如下修改
//反射方向 reflect(入射方向，法线)
//fixed3 reflectDir = normalize(reflect(worldLight, worldNormal));
//视觉方向
fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz - mul(unity_ObjectToWorld, i.vertex).xyz);
//高光公式
fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(saturate(dot(worldNormal, normalize(viewDir+worldLight))), _Gloss);

The self-luminous
C _Emissive = M _Emissive
M _Emissive : a self-luminous colors
achieved:

//高光反射中，定义自发光颜色，在着色器输出最后颜色之前，把自发光颜色添加到输出颜色上即可
o.color = ambine + diffuse + specular+ _Emissive;