Unity——URP填坑——主光源怎么来的？

看到URP中的选择主光源代码，对于每个相机而言，在影响这个相机的光照的所有光源中进行筛选出主光源，过程：首先主光源必须是平行光，然后如果在渲染的环境中设置过Sun的光源，那么就选这个光源为主光源（前提是影响这个相机渲染的，也就是经过Culling的），最后就以亮度最高的（intensity值最大的）为主光源。

static int GetMainLightIndex(UniversalRenderPipelineAsset settings, NativeArray<VisibleLight> visibleLights)
        {
          
   
            using var profScope = new ProfilingScope(null, Profiling.Pipeline.getMainLightIndex);

            int totalVisibleLights = visibleLights.Length;

            if (totalVisibleLights == 0 || settings.mainLightRenderingMode != LightRenderingMode.PerPixel)
                return -1;

            Light sunLight = RenderSettings.sun;
            int brightestDirectionalLightIndex = -1;
            float brightestLightIntensity = 0.0f;
            for (int i = 0; i < totalVisibleLights; ++i)
            {
          
   
                VisibleLight currVisibleLight = visibleLights[i];
                Light currLight = currVisibleLight.light;

                // Particle system lights have the light property as null. We sort lights so all particles lights
                // come last. Therefore, if first light is particle light then all lights are particle lights.
                // In this case we either have no main light or already found it.
                if (currLight == null)
                    break;

                if (currVisibleLight.lightType == LightType.Directional)
                {
          
   
                    // Sun source needs be a directional light
                    if (currLight == sunLight)
                        return i;

                    // In case no sun light is present we will return the brightest directional light
                    if (currLight.intensity > brightestLightIntensity)
                    {
          
   
                        brightestLightIntensity = currLight.intensity;
                        brightestDirectionalLightIndex = i;
                    }
                }
            }

            return brightestDirectionalLightIndex;
        }