Unity Shader 学习 Bump Mapping

实现逻辑

• noraml map

  • 实现逻辑
    �?种方法：1.在切线空间下计算�?.在世界空间下计算。但是由于通用性问题第二种要优于第一种，例如使用CubeMap我们要在世界空间下进行采样�?/p>

    • 在世界空间下计算

      • 在顶点着色器计算从切线空间到世界空间的变换矩�?TBN矩阵 T切线 B副切�?N法线 B可以由TN叉乘获得
        
      • 获得切线空间下的法线纹理数据
      • 将法线纹理数据从切线空间转换到世界空�?/li>

  • Coding

    Shader "Unlit/NoramlShader"
    {
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        [Normal]_NormalMap("Normal Map",2D) = "bump"{}
        _NormalScale("NormalScale",Range(0,1)) = 0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        Pass
        {
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog
    
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl" 
    
            struct appdata
            {
                float4 vertex       : POSITION;
                float2 uv           : TEXCOORD0;
                float3 normal       : NORMAL;
                float4 tangent      : TANGENT;
            };
    
            struct v2f
            {
                float4 pos          : SV_POSITION;
                float2 uv           : TEXCOORD0;
                float3 posWS        : TEXCOORD1;
                float3 nDirWS       : TEXCOORD2;
                float3 tDirWS       : TEXCOORD3;
                float3 bDirWS       : TEXCOORD4;
                
            };
    
            CBUFFER_START(UnityPerMaterial)
                real4 _MainTex_ST;
                real _NormalScale;
            CBUFFER_END
    
            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);
            TEXTURE2D(_NormalMap);
            SAMPLER(sampler_NormalMap);
    
            v2f vert (appdata v)
            {
                v2f o;
                o.posWS = TransformObjectToWorld(v.vertex.xyz);
                o.pos = TransformWorldToHClip(o.posWS);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.nDirWS = TransformObjectToWorldNormal(v.normal);
                o.tDirWS = normalize(TransformObjectToWorldDir(v.tangent.xyz));
                o.bDirWS = normalize(cross(o.nDirWS,o.tDirWS)*v.tangent.w);
                return o;
            }
    
            half4 frag (v2f i) : SV_Target
            {
                float3x3 TBN = float3x3(i.tDirWS,i.bDirWS,i.nDirWS);
                float3 nDirWS = normalize(i.nDirWS);
                float4 normalMap = SAMPLE_TEXTURE2D(_NormalMap,sampler_NormalMap,i.uv); 
                float3 normal = UnpackNormal(normalMap);
                normal.z = sqrt(1.0 - saturate(dot(normal.xy,normal.xy)));
                normal = TransformTangentToWorld(normal,TBN);
                normal = normalize(normal);
                // 混合法线
                nDirWS = lerp(nDirWS,normal,_NormalScale);
    
                Light mainLight = GetMainLight();
                real4 lightColor = real4(mainLight.color, 1);
                float3 lightDir = mainLight.direction;
    
                float nDotL = dot(nDirWS, lightDir);
                float lambert = max(0.0,nDotL);
    
                return lambert.rrrr;
            }
            ENDHLSL
        }
    }
    }