Configure Background of model (transparency?)

[marcoscaceres]

Need to investigate setting the background color (or transparency) of model. Can the formats specify the background color (without using geometry)? Would it use a CSS background color?

[donmccurdy]

I'm not aware that any 3D file formats specify background colors (other than the inverted geometry trick) to be used in a 2D viewport environment. Being able to specify a color or even a texture background on the model element sounds helpful. I am assuming that the color or image background would be visible through any semi-transparent areas of the model, ideally including refraction and physically-based transmission. I would not necessarily require or expect the 3D geometry to refract DOM content behind the element. For example, see the bottom of the page here: https://www.donmccurdy.com/2021/11/11/writing-volumetric-refraction-gltf/

[DR-xR]

If a CSS background is available but not processed in the scene, you could end up with a situation similar to the one illustrated here for : google/model-viewer#3627

[hybridherbst]

I'd like to bump this issue; currently, <model> implementations (Safari, visionOS) always render with a white background, which in most cases does not fit the design requirements of a website.

Additionally, it seems to be not defined how <model> reacts to compositing; my expectation would be that the same things that work with videos (e.g. layering other elements on top of it; round corners; borders) work with <model> as well (but they currently don't). I understand this might be a bug in Apple's implementation, but the spec leaves compositing behaviour open.

Current behaviour of the model element (top) inside a div with blue rounded borders and overflow:hidden. video element (bottom) for comparison.

[zachernuk]

/tpac to discuss whether people would desire a transparent background (which could be useful, but will also be weird)