ScriptableRenderPass applied to only one layer

I’ve looked everywhere and I’m still completely lost on how to implement a post-processing effect using RenderGraph API for ScriptableRenderPass that specifically applies to only a few objects or layers rather than everything in the camera texture.

I followed this tutorial (Unity - Manual: Example of a complete Scriptable Renderer Feature in URP) and it works, but it’s not clear to me how to make modifications to it to make the effect selective, since the shader is working on the entire camera texture in the example.

I’m looking at this example (Graphics/Packages/com.unity.render-pipelines.universal/Samples~/URPRenderGraphSamples/RendererList/RendererListRenderFeature.cs at master · Unity-Technologies/Graphics · GitHub) where it uses a layer mask, and I can’t make heads or tails out of what it’s even doing. The blur example from the documentation doesn’t even call SetRenderFunc().

Can someone please show me what modifications would need to be made to the API calls in the blur example above for the pass to apply the blur effect to just a single layer? My basic understanding is that the layer in question would need to be culled from the scene, rendered independently, and then tacked back on.

Thank you so much for your help.

Edit: I also looked at RenderObjectsPass, but they appear constrained to the object’s geometry, meaning that I can’t apply any post processing effects that extend beyond the bounds of the object texture.