Unity URP Shader 基础光照

函数 GetMainLight() 返回一个数据结构 Light

struct Light
{
    half3   direction; // 颜色&强度
    half3   color; // 方向
    half    distanceAttenuation; // 距离衰减
    half    shadowAttenuation; // 阴影衰减
};

Shader "Example/StandardLight" {
    Properties {
        _BaseColor("Base Color", Color)=(1, 1, 1, 1)
    }

    SubShader {
        Tags {
            "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline"
        }

        Pass {
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"

            CBUFFER_START(UnityPerMaterial)

            half4 _BaseColor;
            CBUFFER_END

            struct Attributes
            {
                float4 positionOS : POSITION;
                half3 normal:NORMAL;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                half3 worldNormal:TEXCOORD0;
            };

            Varyings vert(Attributes input)
            {
                Varyings output;
                // 从对象空间到裁剪空间
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.worldNormal = TransformObjectToWorldNormal(input.normal);
                return output;
            }

            half4 frag(Varyings input): SV_Target
            {
                Light mainLight = GetMainLight();
                // saturate(value) 相当于 Mathf.Clamp01(value) 函数，限制值在 [0,1] 区间
                float power = saturate(dot(mainLight.direction, input.worldNormal)); // 计算漫反射的强度
                half4 output = _BaseColor * power * half4(mainLight.color, 1); //将表面颜色，漫反射强度和光源强度混合。
                return output;
            }
            ENDHLSL
        }
    }
}