Shader-Diffuse(Half Lambert)

// Upgrade NOTE: replaced '_World2Object' with 'unity_WorldToObject'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'


Shader "Unity Shaders Book/Chapter 6/Half Lambert" {
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;
float3 normal : NORMAL;
};

struct v2f {
float4 pos : SV_POSITION;
float3 worldNormal : TEXCOORD0;
};

v2f vert(a2v v) {
v2f o;
// Transform the vertex from object space to projection space
o.pos = UnityObjectToClipPos(v.vertex);

// Transform the normal from object space to world space
o.worldNormal = mul(v.normal, (float3x3)unity_WorldToObject);

return o;
}

fixed4 frag(v2f i) : SV_Target {
// Get ambient term
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;

// Get the normal in world space
fixed3 worldNormal = normalize(i.worldNormal);
// Get the light direction in world space
fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);

// Compute diffuse term
fixed halfLambert = dot(worldNormal, worldLightDir) * 0.5 + 0.5;
fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * halfLambert;

fixed3 color = ambient + diffuse;

return fixed4(color, 1.0);
}

ENDCG
}
} 
FallBack "Diffuse"

}

取自《Unity Shader 入门精要》

半兰伯特(Half-Lambert)光照模型

内容同基层的Diffuse类似，只是把cos值从[-1,1]变为[0,1]

无现实物理意义，原先的[-1,0)是舍弃掉的，现在变成了[0,0.5)，于是物体表面的背后光也能照亮物理了

适用于能透光的材质（玉、纸张等）