参考 《unity shader 入门精要》
这里说的法线纹理是储存切线空间数据 的法线纹理
根据光照的计算分为切线空间下的实现和世界空间下的实现
切线空间下的实现:指的是光照在切线空间下计算。(性能优先)
世界空间下的实现:指的是光照在世界空间下计算。(通用性优先,Cubemap环境映射需要这种方式实现)
切线空间的构建
x轴:tangent切线方向;y轴:副切线方向(或者副法线);z轴:normal法线方向
副切线的获取:float3 binormal = cross(v.normal,v.tangent.xyz)*v.tangent.w;
根据x轴和z轴做叉乘获取垂直这两个轴所在平面的向量,有两个方向,根据v.tangent.w 来确定最后的方向;
然后构建空间变换矩阵float3x3 rotation = float3x3(v.tangent.xyz,binormal,v.normal);
0X01 切线空间下的实现 |
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Book/07.TangentNormal"
{
//法线贴图
Properties
{
_Color ("Color Tint",Color)=(1,1,1,1)
_MainTex ("Main Tex", 2D) = "white" {}
_BumpMap("Normal Map",2D) = "white" {}
_BumpScale("Bump Scale",Float) = 1.0
_Specular("Specular",Color) = (1,1,1,1)
_Gloss("Gloss",Range(8.0,256)) = 20
}
SubShader
{
Pass
{
Tags { "LightMode"="ForwardBase" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
//#pragma multi_compile_fog
#include "UnityCG.cginc"
#include "Lighting.cginc"
float4 _Color,_Specular;
sampler2D _MainTex;
sampler2D _BumpMap;
float _BumpScale,_Gloss;
float4 _MainTex_ST;
float4 _BumpMap_ST;
struct a2v
{
float4 vertex : POSITION;
float3 normal: NORMAL;
float4 tangent:TANGENT;
float2 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float4 uv : TEXCOORD0;
float3 lightDir:TEXCOORD1;
float3 viewDir:TEXCOORD2;
};
v2f vert (a2v v)
{
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv.xy = v.texcoord.xy*_MainTex_ST.xy + _MainTex_ST.zw;
o.uv.zw = v.texcoord.xy*_BumpMap_ST.xy + _BumpMap_ST.zw;
float3 binormal = cross(v.normal,v.tangent.xyz)*v.tangent.w;
float3x3 rotation = float3x3(v.tangent.xyz,binormal,v.normal);
//TANGENT_SPACE_ROTATION;
//将光源位置减去顶点位置,这样就得到光照方向了 — 但是我们应该首先将顶点位置乘上光源的w分量,如果是平行光,w分量为0,得到的结果为0,说明顶点位置全变为(0.0, 0.0, 0.0)了,这样光照方向就是光源本身的位置(return objSpaceLightPos.xyz)。对于点光源,w为1,所以乘上顶点位置后,顶点位置无变化,这样计算的光照方向就是(return objSpaceLightPos.xyz – v.xyz)。
float3 lightDir = mul(unity_WorldToObject,_WorldSpaceLightPos0).xyz - v.vertex*_WorldSpaceLightPos0.w;
o.lightDir = mul(rotation,lightDir);
float3 viewDir = mul(unity_WorldToObject,float4(_WorldSpaceCameraPos,1)).xyz-v.vertex.xyz;
o.viewDir = mul(rotation,viewDir);
o.viewDir = normalize(o.viewDir);
o.lightDir = normalize(o.lightDir);
return o;
}
fixed4 frag (v2f i) : SV_Target
{
i.viewDir = normalize(i.viewDir);
i.lightDir = normalize(i.lightDir);
//uppack normal
fixed3 tangentNormal;
fixed4 packedNormal = tex2D(_BumpMap,i.uv.zw);
#if defined(UNITY_NO_DXT5nm)
tangentNormal.xyz = packedNormal.xyz*2 -1;
#else
// --rgba -- xyzw
//DXTnm 格式中a通道(即w分量)对应发现x分量,g通道(即y分量)对应发现y分量,
//tangentNormal.xy = packedNormal.ag*2 -1;
tangentNormal.xy = packedNormal.wy*2 -1;
tangentNormal=tangentNormal* _BumpScale;
tangentNormal.z = sqrt(1.0-max(0,dot(tangentNormal.xy,tangentNormal.xy)));
#endif
fixed3 albedo = tex2D(_MainTex,i.uv).rgb*_Color.rgb;
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz*albedo;
fixed3 diffuse = _LightColor0.rgb*albedo*max(0,dot(tangentNormal,i.lightDir));
fixed3 halfDir = normalize(i.lightDir+i.viewDir);
fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(max(0,dot(tangentNormal,halfDir)),_Gloss);
return fixed4(ambient+diffuse+specular,1.0);
}
ENDCG
}
}
FallBack "Specular"
}
0X02 世界空间下的实现 |
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader "Book/07.WorldNormal"
{
//法线贴图
Properties
{
_Color ("Color Tint",Color)=(1,1,1,1)
_MainTex ("Main Tex", 2D) = "white" {}
_BumpMap("Normal Map",2D) = "white" {}
_BumpScale("Bump Scale",Float) = 1.0
_Specular("Specular",Color) = (1,1,1,1)
_Gloss("Gloss",Range(8.0,256)) = 20
}
SubShader
{
Pass
{
Tags { "LightMode"="ForwardBase" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
//#pragma multi_compile_fog
#include "UnityCG.cginc"
#include "Lighting.cginc"
#include "AutoLight.cginc"
float4 _Color,_Specular;
sampler2D _MainTex;
sampler2D _BumpMap;
float _BumpScale,_Gloss;
float4 _MainTex_ST;
float4 _BumpMap_ST;
struct a2v
{
float4 vertex : POSITION;
float3 normal: NORMAL;
float4 tangent:TANGENT;
float2 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float4 uv : TEXCOORD0;
float3 worldPos: TEXCOORD1;
float3 mat1: TEXCOORD2;
float3 mat2: TEXCOORD3;
float3 mat3: TEXCOORD4;
};
v2f vert (a2v v)
{
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.worldPos= mul(unity_ObjectToWorld,v.vertex);
o.uv.xy = v.texcoord.xy*_MainTex_ST.xy + _MainTex_ST.zw;
o.uv.zw = v.texcoord.xy*_BumpMap_ST.xy + _BumpMap_ST.zw;
//float3 worldNormal = mul((float3x3)unity_ObjectToWorld,v.normal);
float3 worldNormal = mul(v.normal,(float3x3)unity_WorldToObject);
float3 worldTangent= mul((float3x3)unity_ObjectToWorld,v.tangent.xyz).xyz;
float3 worldBinormal = cross(worldNormal,worldTangent.xyz)*v.tangent.w;
o.mat1=worldTangent.xyz;
o.mat2 = worldBinormal;
o.mat3 = worldNormal;
return o;
}
fixed4 frag (v2f i) : SV_Target
{
float3 lightDir = _WorldSpaceLightPos0.xyz - i.worldPos*_WorldSpaceLightPos0.w;
lightDir = normalize(lightDir);
float3 viewDir = _WorldSpaceCameraPos.xyz - i.worldPos;
viewDir = normalize(viewDir);
float3x3 rotation = float3x3(i.mat1,i.mat2,i.mat3);
//uppack normal
fixed3 tangentNormal;
fixed4 packedNormal = tex2D(_BumpMap,i.uv.zw);
#if defined(UNITY_NO_DXT5nm)
tangentNormal.xyz = packedNormal.xyz*2 -1;
#else
// --rgba -- xyzw
//DXTnm 格式中a通道(即w分量)对应发现x分量,g通道(即y分量)对应发现y分量,
//tangentNormal.xy = packedNormal.ag*2 -1;
tangentNormal.xy = packedNormal.wy*2 -1;
tangentNormal=tangentNormal* _BumpScale;
tangentNormal.z = sqrt(1.0-max(0,dot(tangentNormal.xy,tangentNormal.xy)));
#endif
float3 worldNormal = mul(rotation,tangentNormal);
fixed3 albedo = tex2D(_MainTex,i.uv).rgb*_Color.rgb;
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz*albedo;
fixed3 diffuse = _LightColor0.rgb*albedo*max(0,dot(worldNormal,lightDir));
fixed3 halfDir = normalize(lightDir+viewDir);
fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(max(0,dot(worldNormal,halfDir)),_Gloss);
return fixed4(ambient+diffuse+specular,1.0);
}
ENDCG
}
}
}