使用法线

  • 高度图

    存储的是强度值,用来表现模型表面的海拔高度,颜色越浅越向外凸,颜色越深则相反,好处是非常直观,缺点是计算复杂

    想要和法线一样使用:纹理类型设置为normal map,勾选create from Grayscale

    • Bumpiness:控制凹凸程度
    • Filtering:法线的纹理平滑或者尖锐
  • 法线纹理

    • 法线的范围在[-1,1],像素范围在[0,1],所以在制作法线贴图时,需要把法线映射到像素,在使用法线贴图时,需要把像素映射回法线。

    • 模型空间的法线纹理:即模型空间的表面法线

      优点:简单直观,可以提供平滑的边界。

      缺点:自由度低

    • 切线空间的法线纹理:每个顶点的法线方向为z轴,x轴是切线方向,y轴则是两个方向叉积的方向(副切线)

      优点:可以用于其他模型做效果,可以移动uv制作效果,可以重复用uv,可以压缩。

      缺点:边缘处容易有缝合迹象

在切线空间下计算:效率高

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

Shader "Unity Shaders Book/Chapter 7/Normal Map In Tangent Space" {
Properties {
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_MainTex ("Main Tex", 2D) = "white" {}
//导入法线纹理
_BumpMap ("Normal Map", 2D) = "bump" {}
//设置法线强度
_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

#include "Lighting.cginc"

fixed4 _Color;
sampler2D _MainTex;
float4 _MainTex_ST;
//法线和法线强度
sampler2D _BumpMap;
float4 _BumpMap_ST;

float _BumpScale;
fixed4 _Specular;
float _Gloss;

struct a2v {
float4 vertex : POSITION;
float3 normal : NORMAL;
//需要传入切线,用来计算,第四个参数用来确定切线的方向
float4 tangent : TANGENT;
float4 texcoord : TEXCOORD0;
};

struct v2f {
float4 pos : SV_POSITION;
float4 uv : TEXCOORD0;
float3 lightDir: TEXCOORD1;
float3 viewDir : TEXCOORD2;
};

// Unity doesn't support the 'inverse' function in native shader
// so we write one by our own
// Note: this function is just a demonstration, not too confident on the math or the speed
// Reference: http://answers.unity3d.com/questions/218333/shader-inversefloat4x4-function.html
float4x4 inverse(float4x4 input) {
#define minor(a,b,c) determinant(float3x3(input.a, input.b, input.c))

float4x4 cofactors = float4x4(
minor(_22_23_24, _32_33_34, _42_43_44),
-minor(_21_23_24, _31_33_34, _41_43_44),
minor(_21_22_24, _31_32_34, _41_42_44),
-minor(_21_22_23, _31_32_33, _41_42_43),

-minor(_12_13_14, _32_33_34, _42_43_44),
minor(_11_13_14, _31_33_34, _41_43_44),
-minor(_11_12_14, _31_32_34, _41_42_44),
minor(_11_12_13, _31_32_33, _41_42_43),

minor(_12_13_14, _22_23_24, _42_43_44),
-minor(_11_13_14, _21_23_24, _41_43_44),
minor(_11_12_14, _21_22_24, _41_42_44),
-minor(_11_12_13, _21_22_23, _41_42_43),

-minor(_12_13_14, _22_23_24, _32_33_34),
minor(_11_13_14, _21_23_24, _31_33_34),
-minor(_11_12_14, _21_22_24, _31_32_34),
minor(_11_12_13, _21_22_23, _31_32_33)
);
#undef minor
return transpose(cofactors) / determinant(input);
}

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;

///
/// Note that the code below can handle both uniform and non-uniform scales
///

// Construct a matrix that transforms a point/vector from tangent space to world space
fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
fixed3 worldTangent = UnityObjectToWorldDir(v.tangent.xyz);
fixed3 worldBinormal = cross(worldNormal, worldTangent) * v.tangent.w;

/*
float4x4 tangentToWorld = float4x4(worldTangent.x, worldBinormal.x, worldNormal.x, 0.0,
worldTangent.y, worldBinormal.y, worldNormal.y, 0.0,
worldTangent.z, worldBinormal.z, worldNormal.z, 0.0,
0.0, 0.0, 0.0, 1.0);
// The matrix that transforms from world space to tangent space is inverse of tangentToWorld
float3x3 worldToTangent = inverse(tangentToWorld);
*/
//wToT = the inverse of tToW = the transpose of tToW as long as tToW is an orthogonal matrix.
float3x3 worldToTangent = float3x3(worldTangent, worldBinormal, worldNormal);
//TANGENT_SPACE_ROTATION;列出这个宏,我们可以直接使用rotation,即worldToTangent
// Transform the light and view dir from world space to tangent space
o.lightDir = mul(worldToTangent, WorldSpaceLightDir(v.vertex));
o.viewDir = mul(worldToTangent, WorldSpaceViewDir(v.vertex));

///
/// Note that the code below can only handle uniform scales, not including non-uniform scales
///

// Compute the binormal
// float3 binormal = cross( normalize(v.normal), normalize(v.tangent.xyz) ) * v.tangent.w;
// // Construct a matrix which transform vectors from object space to tangent space
// float3x3 rotation = float3x3(v.tangent.xyz, binormal, v.normal);
// Or just use the built-in macro
// TANGENT_SPACE_ROTATION;
//
// // Transform the light direction from object space to tangent space
// o.lightDir = mul(rotation, normalize(ObjSpaceLightDir(v.vertex))).xyz;
// // Transform the view direction from object space to tangent space
// o.viewDir = mul(rotation, normalize(ObjSpaceViewDir(v.vertex))).xyz;

return o;
}

fixed4 frag(v2f i) : SV_Target {
fixed3 tangentLightDir = normalize(i.lightDir);
fixed3 tangentViewDir = normalize(i.viewDir);

// Get the texel in the normal map
//更据存在uv.zw上的纹理坐标进行采样法线
fixed4 packedNormal = tex2D(_BumpMap, i.uv.zw);
fixed3 tangentNormal;
// If the texture is not marked as "Normal map"
// tangentNormal.xy = (packedNormal.xy * 2 - 1) * _BumpScale;
// tangentNormal.z = sqrt(1.0 - saturate(dot(tangentNormal.xy, tangentNormal.xy)));

// Or mark the texture as "Normal map", and use the built-in funciton
//需要映射回[-1,1]
tangentNormal = UnpackNormal(packedNormal);
//z由xy决定,所以xy一定要变成最终结果后再求z
tangentNormal.xy *= _BumpScale;
tangentNormal.z = sqrt(1.0 - saturate(dot(tangentNormal.xy, tangentNormal.xy)));

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, tangentLightDir));

fixed3 halfDir = normalize(tangentLightDir + tangentViewDir);
fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0, dot(tangentNormal, halfDir)), _Gloss);

return fixed4(ambient + diffuse + specular, 1.0);
}

ENDCG
}
}
FallBack "Specular"
}