Shader-基础光照-高光反射光照模型

高光反射计算公式:
我们需要4个参数,光源的颜色和强度,材质的高光反射系数,视角方向和反射方向.
在高光反射中我们要取得反射光线和视线的夹角.
Cg提供了反射光线的函数reflect(i,n)

Specular.png

Specular.png

逐定点光照

1.声明三个属性,_Specular控制高光反射材质,_Diffuse漫反射材质,_Gloss控制高光区域大小

Properties
    {
        _Diffuse("Diffuse",Color) = (1,1,1,1)
        _Specular("Specular",Color) = (1,1,1,1)
        _Gloss("Gloss",Range(8.0,256)) = 20
    }

2.在SubShader语句块中定义Pass语句块,Tags指明光照模式

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

3.定义着色器 包含内置文件 定义结构体 定义与属性相同类型的变量等

CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag
                #include "Lighting.cginc"

                fixed4 _Diffuse;
                fixed4 _Specular;
                float _Gloss;

            struct a2v {
                float4 vertex:POSITION;
                float3 normal:NORMAL;
            };
            struct v2f {
                float4 pos : SV_POSITION;
                float3 color : COLOR;
            };

4.顶点着色器:包含了ambient环境光,diffuse漫反射光,specular高光

v2f vert(a2v v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);                
                float4 ambient = UNITY_LIGHTMODEL_AMBIENT;              
                float3 worldNormal = normalize(mul(v.normal, (float3x3)_World2Object));
                float3 worldLightDir = normalize(_WorldSpaceLightPos0);
                fixed3 diffuse = _LightColor0.rgb*_Diffuse.rgb*saturate(dot(worldNormal, worldLightDir));
                fixed3 reflectDir = normalize(reflect(-worldLightDir, worldNormal));
                fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz - mul(_Object2World,v.vertex).xyz);
                fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(saturate(dot(reflectDir, viewDir)), _Gloss);
                
                o.color = ambient + diffuse + specular;

                return o;
            }

5.片元着色器:输出色彩

fixed4 frag(v2f i):SV_Target {
                return fixed4(i.color, 1.0);
            }

逐像素光照

Specular_fragment.png

逐像素渲染光照更加平滑
将光照的处理交给fragment
实现完整的Phong光照模型

            struct v2f {
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
            };

            v2f vert(a2v v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
                o.worldNormal = mul(v.normal, (float3x3)unity_WorldToObject);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex);

                return o;
            }
            fixed4 frag(v2f i):SV_Target {
                float4 ambient = UNITY_LIGHTMODEL_AMBIENT;
                float3 worldNormal = normalize(i.worldNormal);
                float3 worldLightDir = normalize(_WorldSpaceLightPos0);
                fixed3 diffuse = _LightColor0.rgb*_Diffuse.rgb*saturate(dot(worldNormal, worldLightDir));
                fixed3 reflectDir = normalize(reflect(-worldLightDir, worldNormal));
                fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz - i.worldPos.xyz);
                fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(saturate(dot(reflectDir, viewDir)), _Gloss);

                fixed3 color = ambient + diffuse + specular;

                return fixed4(color, 1.0);
            }

Blinn-Phong光照模型

Blinn.png

在Blinn模型中我们引入一个新的矢量h

Blinn-Phong.png

得到一个新的公式

fixed3 halfDir = normalize(worldLightDir + viewDir);
fixed3 specular = _LightColor0.rgb*_Specular.rgb*pow(saturate(dot(worldNormal,halfDir)), _Gloss);

更改高光部分的代码

Specular_Blinn-Phong.png

对比Phong模型,高光部分更加明显