渐变纹理

fixed halfLambert = 0.5 * dot(worldNormal, worldLightDir) + 0.5;
fixed3 diffuseColor = tex2D(_RampTex, fixed2(halfLambert, halfLambert)).rgb * _Color.rgb;

关键代码有两行

• 第一行代码获得了法线和光线方向的夹角的余弦值*0.5 + 0.5, 即把余弦值映射到[0, 1]。
• 第二行代码在渐变纹理上采样

Shader "UnityShaderLearning/RampTexture" 
{
    Properties
    {
        _Color ("Color Tint", Color) = (1,1,1,1)
        _RampTex ("Ramp Tex", 2D) = "white" {}
        _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 _RampTex;
            float4 _RampTex_ST;
            fixed4 _Specular;
            float _Gloss;

            struct a2v
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float4 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
                float2 uv : TEXCOORD2;
            };

            v2f vert(a2v v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                o.uv = TRANSFORM_TEX(v.texcoord, _RampTex);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
                fixed halfLambert = 0.5 * dot(worldNormal, worldLightDir) + 0.5;
                fixed3 diffuseColor = tex2D(_RampTex, fixed2(halfLambert, halfLambert)).rgb * _Color.rgb;
                fixed3 diffuse = _LightColor0.rgb * diffuseColor;
                fixed3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
                fixed3 halfDir = normalize(worldLightDir + viewDir);
                fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0, dot(worldNormal, halfDir)), _Gloss);

                return fixed4(ambient + diffuse + specular, 1.0);
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}