Original comment: #130355 (comment)

This is a bit of a yak shave.

• To account for how filters will offset bounds of drawn inputs, we need an interface to query this information given bounds for a set of filter inputs.
• But in order to use that API, filters need to have already been instantiated.
• But our static generators for instantiating filters expect all filter inputs to be supplied upfront.
• In order to make filter inputs optional and set them later, we'll need an easy way to set the inputs for all leaf nodes in the graph.

Having placeholder inputs that behave like a dataless texture/snapshot would also be useful for querying transformed bounds for coverage computations.

Another interesting longterm architectural solution that's worth thinking about: Create an EntityPassContents wrapper (or maybe just an EntityPassFilterInput) that knows how to compute coverage for and render an EntityPass, and then just plug that into the filter graph as the input and let everything unfold normally.