Unity Shader学习笔记（4）切线 & 世界空间下法线的使用

shader主要实现效果：

（1）法线贴图使用；
（2）利用法线贴图影响表面发射计算Specular；

主要代码：

//切线空间和世界空间计算 法线 贴图的使用；
//制作人：嘿皮土豆；
//参考：《Unity Shader入门精要》

Shader "ShaderLearn/NormalMapApply"
{
    Properties 
    {
        _MainColor("MainColor",Color) = (1,1,1,1)

        _MainTex("MainTex",2D) = ""{}
        _BumpMap("NormalMap",2D) = "bump"{}

        _BumpScale("BumpScale",range(0,5)) = 1
        _SpecularColor("SpecularColor",Color) = (1,1,1,1)
        _Gloss("Gloss",range(1,50)) = 0.2

    }
    SubShader
    {
        Tags{"LightMode" = "ForwardBase"}

        //如果两个 Pass 的渲染效果不同可选择混合模式
        //Blend SrcAlpha OneMinusSrcAlpha

        pass
        {
            name "TangentSpaceBumpMap"
            CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag

                #include "UnityCG.cginc"
                #include "Lighting.cginc"

                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;
                };

                sampler2D _MainTex;
                sampler2D _BumpMap;
                float4 _MainTex_ST;
                float4 _BumpMap_ST;

                float4 _MainColor;
                fixed4 _SpecularColor;
                float _BumpScale;
                float _Gloss;

                v2f vert (a2v v)
                {
                    v2f o;
                    o.pos = UnityObjectToClipPos(v.vertex);
                    o.uv.xy = TRANSFORM_TEX(v.texcoord, _MainTex);
                    o.uv.zw = TRANSFORM_TEX(v.texcoord, _BumpMap);

                    //float3 binormal = cross(normalize(v.normal),normalize(v.tangent.xyz)) * v.tangent.w;
                    //float3x3 rotation = float3x3 (v.tangent.xyz, binormal, v.normal);

                    //或者直接使用宏；
                    TANGENT_SPACE_ROTATION;
                    o.LightDir = mul(rotation, ObjSpaceLightDir(v.vertex)).xyz;
                    o.ViewDir = mul(rotation, ObjSpaceViewDir(v.vertex)).xyz;
                    return o;
                }

                fixed4 frag (v2f i) : SV_TARGET
                {
                    fixed3 TangentLightDir = normalize(i.LightDir);
                    fixed3 TangentViewDir = normalize(i.ViewDir);

                    //贴图转换（输入四维计算出三维）
                    fixed3 TangentNormal = UnpackNormal(tex2D(_BumpMap,i.uv.zw));

                    //法线贴图强度控制；
                    TangentNormal.xy *= _BumpScale;
                    TangentNormal.z = sqrt(1-saturate(dot(TangentNormal.xy, TangentNormal.xy)));
                    
                    fixed3 albedo = tex2D(_MainTex, i.uv.xy).rgb * _MainColor.rgb;
                    fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
                    fixed3 diffuse = _LightColor0.rgb * albedo * (dot(TangentNormal, TangentLightDir)*0.5+0.5);

                    fixed3 halfDir = normalize(TangentViewDir + TangentLightDir);
                    fixed3 specular = _LightColor0.rgb * _SpecularColor.rgb * pow(saturate(dot(TangentNormal,halfDir)), _Gloss);
                   
                    return fixed4 (ambient + diffuse + specular, 1);

                }

            ENDCG
        }
        
        pass
        {
            name "WorldSpaceBumpMap"
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"

            struct a2v
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float2 uv : TEXCOORD0;
                float4 tangent : TANGENT;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float4 uv : TEXCOORD0;
                float3 TtoW0 : TEXCOORD1;
                float3 TtoW1 : TEXCOORD2;
                float3 TtoW2 : TEXCOORD3;
            };

                sampler2D _MainTex;
                sampler2D _BumpMap;
                float4 _MainTex_ST;
                float4 _BumpMap_ST;

                float4 _MainColor;
                fixed4 _SpecularColor;
                float _BumpScale;
                float _Gloss; 

            v2f vert (a2v v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);

                float3 worldNormal = UnityObjectToWorldNormal(v.normal);
                float3 worldTangent = UnityObjectToWorldDir(v.tangent.xyz);
                float3 worldBinormal = cross(worldNormal, worldTangent)* v.tangent.w;

                o.TtoW0 = float3 (worldTangent.x, worldBinormal.x, worldNormal.x);
                o.TtoW1 = float3 (worldTangent.y, worldBinormal.y, worldNormal.y);
                o.TtoW2 = float3 (worldTangent.z, worldBinormal.z, worldNormal.z);

                o.uv.xy = TRANSFORM_TEX(v.uv, _MainTex);
                o.uv.zw = TRANSFORM_TEX(v.uv, _BumpMap);
                return o;
            }

            fixed4 frag (v2f i) : SV_TARGET
            {
                float3 worldPos = mul(unity_ObjectToWorld, i.vertex).xyz;
                fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(worldPos));
                fixed3 worldViewDir = normalize(UnityWorldSpaceViewDir(worldPos));

                float3 TangentNormal = UnpackNormal(tex2D(_BumpMap,i.uv.zw));

                TangentNormal.xy *= _BumpScale;
                TangentNormal.z = sqrt(1-saturate(dot(TangentNormal.xy, TangentNormal.xy)));

                fixed3 TtoWNormal = fixed3 (dot(i.TtoW0, TangentNormal), dot(i.TtoW1, TangentNormal), dot(i.TtoW2, TangentNormal));

                fixed3 albedo = tex2D(_MainTex,i.uv.xy) * _MainColor;
                fixed3 diffuse = _LightColor0.xyz * albedo * (dot(worldLightDir, TtoWNormal)*0.5+0.5);
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;

                fixed3 halfDir = normalize(worldViewDir + worldLightDir);
                fixed3 specular = _LightColor0.rgb * _SpecularColor.rgb * pow(saturate(dot(TtoWNormal,halfDir)), _Gloss);

                return fixed4 (ambient + diffuse + specular, 1);
            }

            ENDCG
        }
    }
    //Fallback "Specular"
}