Current options on the table include:

• Google licensing model (currently in place)
• Polymer licensing model (BSD 3 Clause, etc)

Especially noticeable on mobile with a large element; even a 400x300 element can make it impossible to scroll.

This may be an addon/mixin that adds a new attribute (some version of source-magicleap, magicleap-source, or source-fbx), and abstracts the <ml-model> tag (passing down parameters from the enclosing <xr-model> into an <ml-model> nested into a shadow root).

Currently several CE lifecycle callbacks have empty implementations. If these aren't needed, we should just remove them.

Instead, these should be generated as part of a prepublish or prepare NPM script.

The list probably includes auto-rotate, orbit-controls, ar, preload (although that list could be trimmed if it reduces scope or complexity). This will help tease out patterns for extensibility.

For release, we need:

• Docs (can be README, or on website) -- any patterns/tools for documenting web component APIs?
  • APIs, caveats, the polyfill story, compatibility matrix, best practices
  • #8
• Ensure all example pages work, and ideally some nice way of navigating them (e.g. three.js demos)
• Maybe a gif for the README

Perhaps create these as optional addons? Would vignette fit into that category?

Related to #56 maybe, but perhaps we can consider only allowing rotation on the Y, and a limit on zooming (or removing, or using a different gesture due to #56?) -- when using a provided image, it's possible to zoom out too far seeing the skysphere, and possible to zoom in too close and the near plane kicks in, or 'get lost' so to speak with no way of resetting.

Can be resolved via -p flag for chokidar for polling, but non-ideal.
paulmillr/chokidar#237

For inline, WebXR, and Magic Leap, we'll need a glTF/glb file. There's a scenario where only the USDZ is provided, with a poster, which is more or less no different from iOS's native AR Quick Look.

This may already work due to the mixin pattern, but something we should confirm, and/or clarify in docs.

https://github.com/immersive-web/webxr-polyfill

It's pedantically correct but potential confusing - including requiring users to know/specify mime-types).

Instead, use a simpler, attribute-based approach. The main glTF resource can remain source, and we can have other optional attributes for source-usdz and potentially source-ml (or source-fbx).

We'll be using GLTFLoader for this, which handles both, but maybe we should be clear on what we're supporting. Related to dynamic lights (#34) which 2.0 has a different light extension.

I have a 3D model and when I tried to load it with <xr-model> it renders at the bottom and a portion of the model gets cut off. See this screenshot:

The same model renders nicely in https://gltf-viewer.donmccurdy.com/ which is what I would expect.

I tried a few 3D models in poly.google.com and they all seem to render a bit off in <xr-model>. It would be nice if the <xr-model> can render the model without needing to adjust it by hand.

Even with WebXR flags enabled/ARCore installed, the ARCore bindings do not ship in Chrome release or beta. This means checking the existence of XRSession.prototype.requestHitTest is insufficient, which will exist when the flags are enabled, even in release. This test was originally used since the initial releases of AR support did not have any flags to distinguish an AR session from a typical VR session, but now there is the temporary session option environmentIntegration that we can use.

requestSession requires a user gesture, but we can call supportsSession({ environmentIntegration: true }) outside of a gesture to test existence of AR support (if WebXR is detected). May also need to pass in the XRPresentationContext in the outputContext session config key.

Related bug: https://bugs.chromium.org/p/chromium/issues/detail?id=898980

This one was tricky earlier and never was fully happy with a solution.

Models can be large, and may want to lazy load the models until an interaction occurs. We can display a poster image in the mean time, but if preload is the default, our "out of the box" model (<xr-model src="..."></xr-model>) would not preload, or if it does preload, it doesn't have a poster to display. We could have some smart options (like never preloading on mobile). But balancing the out of the box experience default params with the ideal user experience is something we'll need to figure out.

Related is what kind of messaging is provided if the user needs to interact with the element before loading a model? "Click to display model"?

We're not confident that our current approach is stable long-term. Is there a better mechanism we can use to discover what capabilities the current device has?

We need to decide on a technical approach, @cdata @jsantell @mrdoob started a discussion.

[Edit @jsantell: Previously "Ensure that we can have as many instances of <xr-model> on a page as desired", using a single webgl context to circumvent the 16 context limit, and for performance improvements]

Thoughts on removing ar attribute? Rational being this should just be for "free" on platforms that can support it, rather than something one explicitly has to ask for.

It should be possible to create a new type of view (e.g., VR, off-screen rendering) as mixins.

Consider renaming 'views' to 'modes' - views is overloaded, and we already refer to these as modes in some of the docs.

Note that it may make sense to have tasks or new issues to create those mixins when we pick this work up.

How do we want this interaction to work if both values are set on a model?

• Does the model continue spinning even after interacting with orbit controls?
• Can only one exist at the same time?
• Does the model auto-rotate until interacting with it, then orbit controls take over, and then after inactivity, go back to rotating? Do we switch back to the lazy susan camera view, or start from where the user left off via the controls?

We may be able to check the size of the element every frame instead.

Our goal is to make it simple, so let's define defaults that look good and are performant. Advanced developers (or users with specific needs) can turn to three.js.

A simple version (recommended by @mrdoob) might be to only use an environment map.

We've been calling this a composer, but we need a simple way to at least:

• Import multiple models, and export as a single model
• Perform simple movements (changing the origin, scaling)
• Preview how the model will appear embedded or in AR

Meta bug, can break out if not handled here. Taken from current readme:

• There is currently no way to tell whether an iOS device has AR Quick Look support. Possibly check for other features added in Safari iOS 12 (like CSS font-display): https://css-tricks.com/font-display-masses/ Are there any better ways?

• Since there are no USDZ three.js loaders (and seems that it'd be difficult to do), Safari iOS users would either need to load a poster image, or if they load the 3D model content before entering AR, they'd download both glTF and USDZ formats, which are already generally rather large. Not sure if this is solvable at the moment, so we may need to just document the caveats.

• With native AR Quick Look, the entire image triggers an intent to the AR Quick Look. Currently in this component implementation, the user must click the AR button. Unclear if we want to change this, as interacting and moving the model could cause an AR Quick Look trigger. Do we want this to appear as native as possible?

• The size of the AR Quick Look native button scales to some extent based off of the wrapper. We could attempt to mimic this, or leverage the native rendering possibly with a transparent base64 image. I've played around with this, but someone with an OSX/iOS device should figure out the rules for the AR button size. I did some prelim tests here: https://ar-quick-look.glitch.me/

• Xr-model cares a lot about measuring changes to attributes / properties over time
• Lit-element covers a lot of ground for measuring changes to attributes / properties over time
• Lit-element is a relatively small dependency with shallow dependency graph https://bundlephobia.com/result?p=@polymer/[email protected]
• Could use the primitive UpdatingElement to save a few bytes https://github.com/Polymer/lit-element/blob/master/src/lib/updating-element.ts

Right now, there are cases where each model having its own GL renderer is more performant than using one renderer (via #50) blitting to 2D canvases. Most cases, actually, but harder to test without a way to flip between rendering strategies.

While working on environment maps, each model will need access to whatever renderer its using to create the appropriate maps, which prompted this issue.

Also include a browser compatibility support/platform requirements matrix

While our vision includes a generic component that supports multiple views (embedded, AR and VR), this first release will support only embedded and AR.

Is there room for a specific embedded and AR component, perhaps with a simpler interface, and show we adjust the name to reflect our initial focus - perhaps to ar-model?

While some content publishers want full control over the scene, there are specifically perf costs for things like shadows and lights. Do we want something like allow-model-lights to import dynamic lights that are found in a glTF model? Would this enable shadows as well? Should this be disabled, even if set, on mobile?

The content author should decide if this is the correct polyfill, or if one's needed at all depending on which browsers they're targeting.

The current/previous WebXR+AR experience was the most crude thing imaginable: a circle appears on a surface when found and tapping places the model there. No other visuals or indications. Very MVP. Open questions surrounding this, and what we need or can do for an initial release:

Stabilizing notification

In the WebXR+AR codelab, a gif is displayed to users indicating they should "look around" with their device as a pose is found. This can take a few seconds in some environments on some phones.

We use this gif with the caveat that there's some compositing jank with it.

Instructions

In the Chacmool AR experience, instructions are rendered to describe how to interact.

Footprint Reticle

In the Chacmool AR experience, the reticle becomes the footprint of the model, and displays additional information regarding the dimensions (once placed, see the other Chacmool image here).

Interaction Controls

Apparently it's difficult to touch the screen and press two buttons to take a screenshot, but you can see some styled touch marks when interacting, and can slide (translate) and rotate the model (via two finger rotate). These interactions are/were non-trivial to get working, probably out of scope for MVP. I think the "pin" button halts the movements.

Exit controls

This seems easy and something we should probably have. The "X" in the upper left in Chacmool example.

Using an Intersection Observer and lazily draw only models in view.

Has decent browser support: https://caniuse.com/#feat=intersectionobserver

Probably should depend on #10.

We have in previous iterations offered a background-image attribute that allows setting an equirectangular image to be used as the skybox, as well as an environment map. Is this something we want?

While we could use ImageBitmapRenderingContext in the main thread and blit textures using that instead of Canvas2DRenderingContexts in a more efficient way, the bitmap rendering and offscreen canvas APIs are related and if supported, should both be available, meaning we can always do rendering in a worker for this codepath. We could transferControlToOffscreen for each model element, and then we'd have multiple WebGL contexts in a worker, or multiple workers, but unclear if that's more performant than a single context in a worker sending out textures. Also if one can crop the bitmaps created from there.

More info: #10 (comment)

Dependent on #10 in some cases, but after writing this, now I'm not sure.

We discussed that having a hosted version of the component on a CDN that could be easily included would be helpful.

There are a few use cases we should support:

• A fully bundled release (including all polyfills and three.js)
• An unbundled release (for users who already have three.js)
• A specifically versioned URL for stability
• A 'latest stable' URL to always get the latest & greatest

Where to host this is TBD. We should include links in the README so this is discoverable.