Presentation as a first-class DOM element

While most of the issues about HTMLModelElement relate what it's displaying (i.e. 3D rendered content, animated and then lit by some lighting environment), it's also important to consider how it's presented in the page, alongside other DOM elements. What are requirements that need to apply?

For example, while it's not "realistic" to be able to construct a blurred 3D model, alter its contrast or to apply grayscale or sepia toning, these are mainstays of DOM representation - both with direct filter CSS directives on an element's hierarchy, or based on backdrop-filter directives on anything on top. While it may seem niche to feature these filtering environments, it's a frequent issue on sites with paywalls (think nytimes.com) or sites with position:sticky elements leveraging backdrop-filter:blur() presentation (like apple.com)

Similarly, it's clear that a monoscopic (or un-tracked) presentation of a Model can accommodate a fully transparent background, it's not immediately clear that other DOM content should be visible "behind" a model, particularly when it's displayed as on the surface of a page rather than in the portal behind it.

/agenda

Start by reviewing the HTMLModelElement presentation requirements described in the issue, especially CSS filter, backdrop-filter, transparency, and visibility of surrounding DOM content. Define the expected behavior for model presentation in-page and portal contexts; done means the requirements are explicit enough to guide implementation.