Thanks for spotting the issue. I have merged and then updated the built-in ShaderSets within the VSG itself:

vsg-dev/VulkanSceneGraph@d3c67c1

I thought I had put in a check for intensity to avoid assigning lights that are off to the ViewDependentState's lightData but I have just done a code review and haven't spotted one. I think the right way to tackle that wold be to add a check to the RecordtTraversal::apply(*Light&) implementations so that the lights that are off aren't added at all.

I will have a think about the required mods to RecordTraversal.

Thanks.

Do you have a scene that tests out the lights with low intensity?

In our railway game we made GUI that change common ambient and directional lights. Now we are working to add headlight for our rolling stock, by add spotlights to its .gltf with KHR_lights_punctual. And we found that every off spotlight broke all next spots, as well turning to zero directional broke all spots. Now it works correct.
Not sure that we may suggest something for creating tests in vsgExamples.

I have added a RecordTraversal::intensityMinimum control for culling lights that are switched off via the intensity.

vsg-dev/VulkanSceneGraph@adb8770

Could you test VSG master?

Test with new master and old shader with early check. Yes, it works too. I think RecordTraversal::intensityMinimum by default should be the same 0.001f as default brightnessCutoff value in shaders, not 0.00001

As well as default values it make be worth changing the naming to make it more consistent.

May also be worth passing the value to the shader, though this involves extra complexity. For now I'll stick with simplicity.