我们需要修改着色器代码，以便让水体材质受到场景中的定向光影响。一种可能的实现方式是在着色器中添加一个方向向量，并将其与定向光的方向向量进行点积运算，以确定光的角度和水体的表面法线之间的夹角。在此基础上，我们可以调整水体的反射和折射效果，使其呈现出更加真实的效果。以下是一个基于Unity引擎的示例代码：

Shader "Custom/Water" { Properties { _MainTex("Texture", 2D) = "white" {} _NormalTex("Normal Texture", 2D) = "bump" {} _WaveAmount("Wave Amount", Range(0, 1)) = 0.5 _RefractStrength("Refraction Strength", Range(0, 1)) = 0.5 }

SubShader {
    Tags { "RenderType"="Opaque" }
    LOD 100

    CGPROGRAM
    #pragma surface surf Standard

    sampler2D _MainTex;
    sampler2D _NormalTex;
    float _WaveAmount;
    float _RefractStrength;

    struct Input {
        float2 uv_MainTex;
        float3 worldPos;
        float3 worldNormal;
    };

    void surf (Input IN, inout SurfaceOutputStandard o) {
        // get the normal from the normal map texture
        o.Normal = UnpackNormal(tex2D(_NormalTex, IN.uv_MainTex));

        // calculate the angle between the light direction and the surface normal
        float3 lightDir = _WorldSpaceLightPos0.xyz;
        float angle = max(0, dot(IN.worldNormal, lightDir));

        // calculate the refraction and reflection strength based on the wave amount and angle
        float refractionStrength = 1 - _RefractStrength * _WaveAmount * angle;
        float reflectionStrength = _WaveAmount * angle;

        // apply the texture and adjust the colors based on the refraction and reflection strength
        o.Albedo = tex2D(_MainTex, IN.uv_MainTex).rgb;
        o.Albedo *= refractionStrength;
        o.Metallic = 0;
        o.Specular = 0;
        o.Smoothness = 0.5;

        // adjust the surface normals for refraction
        o.Normal = perturbNormal(o.Normal, o.WorldReflection, IN.world