Immersive Web Newsletter 2!!

 Recent Spec Changes - from 2019-02-22 to 2019-03-29
Here is summary of some of the major merged changes to the immersive web
space over the past month :)
Validate position DOMPointInit
<https://github.com/immersive-web/webxr/pull/568>

Merged Mon Mar 25 2019 - *ed:spec*

Validate position DOMPointInit
Gamepad-based button/axis state
<https://github.com/immersive-web/webxr/pull/499>

Merged Fri Mar 01 2019 - *ed:explainer*, *ed:feature*

Gamepad-based button/axis state (#499)

This commit describes how to access to controller button and axis state for
XRInputSources via a gamepad attribute, which is an instance of the Gamepad
interface described in the Gamepad API. It details the additional
restrictions that apply to gamepads that are exposed in this way, as well
as how they interact with the existing select/selectstart/selectend events.
Remove viewMatrix and add XRTransform.inverse()
<https://github.com/immersive-web/webxr/pull/531>

Merged Fri Mar 08 2019 - *ed:explainer*, *ed:spec*

Remove viewMatrix and add XRRigidTransform.inverse() (#531)

Long-requested API cleanup to get rid of the explicit viewMatrix attribute,
paired with a method for getting the inverse of an XRRigidTransform. The
inverse() method can both be used to get the value that was previously
returned by the viewMatrix (transform.inverse().matrix) and also makes
application of the XRReferenceSpace.originOffset attribute easier if your
use case happens to feel "backwards" from the default behavior.
Add ignoreDepthValues attribute to the XRWebGLLayer
<https://github.com/immersive-web/webxr/pull/548>

Merged Thu Mar 07 2019 - *ed:explainer*, *ed:feature*, *ed:spec*

Add ignoreDepthValues attribute to the XRWebGLLayer (#548)

This value instructs the UA to prevent the values left in the depth buffer
after a frame is rendered for compositing. If left false (the default) the
UA is allowed to use the depth buffer for things like improved reprojection.

Also includes some language specifying how the depth buffer is interpreted
and indicating that reverse-Z projection is acceptable.
Indicate the preferred ergonomics of a tracked-pointer ray
<https://github.com/immersive-web/webxr/pull/524>

Merged Mon Feb 25 2019 - *ed:spec*

Indicate the preferred ergonomics of a tracked-pointer ray (#524)
Specify that getViewerPose throws an error for non-rAF XRFrames
<https://github.com/immersive-web/webxr/pull/535>

Merged Fri Feb 22 2019 - *ed:explainer*, *ed:spec*

Specify that getViewerPose throws an error unless the frame come from a rAF
call.
Spec: Stationary subtype support is all-or-nothing
<https://github.com/immersive-web/webxr/pull/537>

Merged Mon Feb 25 2019 - *ed:spec*

Spec: Stationary subtype support is all-or-nothing (#537)
added a few AR device examples
<https://github.com/immersive-web/webxr/pull/538>

Merged Mon Feb 25 2019 - *ed:explainer*

added a few AR device examples
Allow flexible depth for screen-based ray input
<https://github.com/immersive-web/webxr/pull/573>

Merged Tue Mar 26 2019 - *ed:explainer*

Allow flexible depth for screen-based ray input

For screen-based input, it seems overly specific to require that the ray
origin must be at the near plane. If the system knows the actual position
of the screen in 3D space, i.e. for a zSpace-style display or for
smartphone AR, it would be preferable to use the actual mapping of the
touch point into virtual world space for this. For example, if you use
touch controls to add bubbles or other particle effects to the scene, it
would look most natural to have those actually originate at the touched
point.

As an additional complication,
https://github.com/immersive-web/webxr/pull/548 changed the core spec to
explicitly allow reversed-Z where depthFar is less than depthNear. If the
actual screen plane isn't available, it would be more consistent to use the
closer of the two instead of always using depthNear.

As far as I can tell the spec itself doesn't currently require any
particular depth for XRTargetRayMode screen.

See also
https://github.com/immersive-web/webxr/issues/489#issuecomment-455291966 -
I think it's problematic to assume that the screen plane corresponds to the
near plane.
Spec text for the identity reference space
<https://github.com/immersive-web/webxr/pull/520>

Merged Tue Mar 05 2019 - *ed:spec*

Spec text for the identity reference space (#520)

Adds text and algortihms detailing the creation of the identity reference
space to the spec.
Spec: Move outputContext to XRRenderState
<https://github.com/immersive-web/webxr/pull/536>

Merged Tue Mar 19 2019 - *ed:spec*

Spec: Move outputContext to XRRenderState (#536)

This change makes the outputContext part of the Session's render state, as
is outlined in the explainer, so that it can be managed by the same timing
as the rest of the state. This change requires slightly more logic than
other render state values since it may need to remove the outputContext
from a session that it was previously assigned to.
Explainer: requestReferenceSpace no longer takes an array
<https://github.com/immersive-web/webxr/pull/554>

Merged Thu Mar 07 2019 - *ed:spec*

requestReferenceSpace no longer takes an array

This change brings the explainer's IDL signature back inline with the
version that's in the spec until we determine once and for all if we should
allow this function to accept an array or not.Tellingly, despite multiple
code examples using requestReferenceSpace only one, the one explicitly
showing the fallback behavior, was actually using the "correct" form of the
call prior to this PR.