Simplify available spaces (#626)

toji · web-flow · commit 9730caccdb36 · 2019-05-09T15:29:37.000-07:00
Removes the position-disabled reference space from the spec and
explainers. Developers that wish to display the types of content this
reference space supported (primarily 360 media) should instead manually
zero-out the position of the XRView transforms when rendering.

Also consolidates the viewerSpace attribute and the identity reference
space into a single new reference space called viewer. This new
space is functionally equivalent to the previous viewerSpace but
fetched via requestReferenceSpace() with the same guarantee of
availability as identity had previously. All other spaces relate to it
like any other space.
diff --git a/index.bs b/index.bs
@@ -363,7 +363,6 @@ enum XREnvironmentBlendMode {
   // Attributes
   readonly attribute XREnvironmentBlendMode environmentBlendMode;
   [SameObject] readonly attribute XRRenderState renderState;
-  [SameObject] readonly attribute XRSpace viewerSpace;
 
   // Methods
   void updateRenderState(optional XRRenderStateInit state);
@@ -389,8 +388,6 @@ enum XREnvironmentBlendMode {
 
 Each {{XRSession}} has a <dfn for="XRSession">mode</dfn>, which is one of the values of {{XRSessionMode}}.
 
-The {{XRSession/viewerSpace}} on an {{XRSession}} has a <dfn for="XRSession/viewerSpace">list of views</dfn>, which is a [=/list=] of [=view=]s corresponding to the views provided by the [=/XR device=].
-
 <div class="algorithm" data-algorithm="initialize-session">
 
 To <dfn>initialize the session</dfn>, given |session| and |mode|, the user agent MUST run the following steps:
@@ -495,9 +492,7 @@ The <dfn attribute for="XRSession">environmentBlendMode</dfn> attribute returns
 
 NOTE: Most Virtual Reality devices exhibit {{XREnvironmentBlendMode/opaque}} blending behavior. Augmented Reality devices that use transparent optical elements frequently exhibit {{XREnvironmentBlendMode/additive}} blending behavior, and Augmented Reality devices that use passthrough cameras frequently exhibit {{XREnvironmentBlendMode/alpha-blend}} blending behavior.
 
-The <dfn attribute for="XRSession">viewerSpace</dfn> attribute is an {{XRSpace}} with a [=native origin=] that tracks the pose of the [=viewer=].
-
-NOTE: For any given {{XRFrame}} calling {{XRFrame/getPose()}} with the {{XRSession/viewerSpace}} and any {{XRReferenceSpace}} will return the same pose (without the {{views}} array) as calling {{XRFrame/getViewerPose()}} with the same {{XRReferenceSpace}}.
+Each {{XRSession}} has a <dfn for="XRSession">viewer reference space</dfn>, which is an {{XRReferenceSpace}} of type {{XRReferenceSpaceType/viewer}} with an [=identity transform=] [=XRSpace/origin offset=]. The [=XRSession/viewer reference space=] has a <dfn for="XRSession/viewer reference space">list of views</dfn>, which is a [=/list=] of [=view=]s corresponding to the views provided by the [=/XR device=].
 
 <section class="unstable">
 The <dfn attribute for="XRSession">onblur</dfn> attribute is an [=Event handler IDL attribute=] for the {{blur}} event type.
@@ -688,10 +683,10 @@ When the <dfn method for="XRFrame">getViewerPose(|referenceSpace|)</dfn> method
   1. Let |session| be |frame|'s {{XRFrame/session}} object.
   1. If |frame|'s [=animationFrame=] boolean is <code>false</code>, throw an {{InvalidStateError}} and abort these steps.
   1. Let |pose| be a new {{XRViewerPose}} object.
-  1. [=Populate the pose=] of |session|'s {{XRSession/viewerSpace}} in |referenceSpace| at the time represented by |frame| into |pose|.
+  1. [=Populate the pose=] of |session|'s [=XRSession/viewer reference space=] in |referenceSpace| at the time represented by |frame| into |pose|.
   1. If |pose| is <code>null</code> return <code>null</code>.
   1. Let |xrviews| be an empty [=/list=].
-  1. For each [=view=] |view| in the [=XRSession/viewerSpace/list of views=] on the {{XRSession/viewerSpace}} of {{XRFrame/session}}, perform the following steps:
+  1. For each [=view=] |view| in the [=XRSession/viewer reference space/list of views=] on the[=XRSession/viewer reference space=] of {{XRFrame/session}}, perform the following steps:
       1. Let |xrview| be a new {{XRView}} object.
       1. Initialize |xrview|'s {{XRView/eye}} to |view|'s [=view/eye=]
       1. Initialize |xrview|'s {{XRView/projectionMatrix}} to |view|'s [=view/projection matrix=]
@@ -760,8 +755,7 @@ An {{XRReferenceSpace}} is one of several common {{XRSpace}}s that applications
 
 <pre class="idl">
 enum XRReferenceSpaceType {
-  "identity",
-  "position-disabled",
+  "viewer",
   "eye-level",
   "floor-level",
   "bounded",
@@ -780,9 +774,7 @@ Each {{XRReferenceSpace}} has a <dfn for="XRReferenceSpace">type</dfn>, which is
 
 An {{XRReferenceSpace}} is most frequently obtained by calling {{XRSession/requestReferenceSpace()}}, which creates an instance of an {{XRReferenceSpace}} or an interface extending it, determined by the {{XRReferenceSpaceType}} enum value passed into the call. The type indicates the tracking behavior that the reference space will exhibit:
 
-  - Passing a type of <dfn enum-value for="XRReferenceSpaceType">identity</dfn> creates an {{XRReferenceSpace}} instance. It represents a tracking space with a [=native origin=] that tracks the position and orientation of the [=viewer=]. For {{XRSession}}s without tracking data, the [=native origin=] stays constant. Only the {{XRSession/viewerSpace}} and {{XRInputSource/targetRaySpace}}'s of {{XRInputSource}}'s with an {{XRInputSource/targetRayMode}} of {{XRTargetRayMode/screen}} can be spatially related to an {{identity}} reference space.
-
-  - Passing a type of <dfn enum-value for="XRReferenceSpaceType">position-disabled</dfn> creates an {{XRReferenceSpace}} instance.  It represents a tracking space with a [=native origin=] that tracks the position of the [=viewer=], with a constant orientation initialized based on the conventions of the underlying [=/XR device=]. It can be used to create experiences where the movement of the user is disregarded, as it will not report changes in position when used with {{XRFrame/getViewerPose()}}.
+  - Passing a type of <dfn enum-value for="XRReferenceSpaceType">viewer</dfn> creates an {{XRReferenceSpace}} instance. It represents a tracking space with a [=native origin=] which tracks the position and orientation of the [=viewer=].
 
   - Passing a type of <dfn enum-value for="XRReferenceSpaceType">eye-level</dfn> creates an {{XRReferenceSpace}} instance. It represents a tracking space with a [=native origin=] near the user's head at the time of creation. The exact position and orientation will be initialized based on the conventions of the underlying platform. When using this reference space the user is not expected to move beyond their initial position much, if at all, and tracking is optimized for that purpose. For devices with [=6DoF=] tracking, {{eye-level}} reference spaces should emphasize keeping the origin stable relative to the user's environment.
 
@@ -792,9 +784,7 @@ An {{XRReferenceSpace}} is most frequently obtained by calling {{XRSession/reque
 
   - Passing a type of <dfn enum-value for="XRReferenceSpaceType">unbounded</dfn> creates an {{XRReferenceSpace}} instance if supported by the [=/XR device=] and the {{XRSession}}. It represents a tracking space where the user is expected to move freely around their environment, potentially even long distances from their starting point. Tracking in an {{unbounded}} reference space is optimized for stability around the user's current position, and as such the [=native origin=] may drift over time.
 
-Devices that support any of the following {{XRReferenceSpaceType}}s MUST support all three: {{XRReferenceSpaceType/position-disabled}}, {{XRReferenceSpaceType/eye-level}}, {{XRReferenceSpaceType/floor-level}}. The minimum sensor data necessary for supporting all three reference spaces is the same.
-
-Note: The {{position-disabled}} type is primarily intended for use with pre-rendered media such as panoramic photos or videos. It should not be used for most other media types due to user discomfort associated with the lack of a neck model or full positional tracking.
+Devices that support {{XRReferenceSpaceType/eye-level}} reference spaces MUST support {{XRReferenceSpaceType/floor-level}} reference spaces, through emulation if necessary, and vice versa.
 
 The <dfn attribute for="XRReferenceSpace">onreset</dfn> attribute is an [=Event handler IDL attribute=] for the {{reset}} event type.
 
@@ -859,7 +849,7 @@ An {{XRView}} describes a single <dfn>view</dfn> into an XR scene for a given fr
 
 Each [=view=] corresponds to a display or portion of a display used by an XR device to present imagery to the user. They are used to retrieve all the information necessary to render content that is well aligned to the [=view=]'s physical output properties, including the field of view, eye offset, and other optical properties. [=Views=] may cover overlapping regions of the user's vision. No guarantee is made about the number of [=views=] any XR device uses or their order, nor is the number of [=views=] required to be constant for the duration of an {{XRSession}}.
 
-A [=view=] has an associated internal <dfn>view offset</dfn>, which is an {{XRRigidTransform}} describing the position and orientation of the [=view=] in the {{XRSession/viewerSpace}}'s [=coordinate system=].
+A [=view=] has an associated internal <dfn>view offset</dfn>, which is an {{XRRigidTransform}} describing the position and orientation of the [=view=] in the [=XRSession/viewer reference space=]'s [=coordinate system=].
 
 A [=view=] has an associated <dfn for="view">projection matrix</dfn>which is a [=matrix=] describing the projection to be used when rendering the [=view=], provided by the underlying XR device. The [=view/projection matrix=] MAY include transformations such as shearing that prevent the projection from being accurately described by a simple frustum.
 
diff --git a/input-explainer.md b/input-explainer.md
@@ -89,7 +89,7 @@ function onSessionStarted(session) {
 }
 ```
 
-All three events are `XRInputSourceEvent` events. When fired the event's `inputSource` attribute will contain the `XRInputSource` that produced the event. The event's `frame` attribute will contain a valid `XRFrame` that can be used to call `getPose()` at the time the selection event occurred. Calling the frame's `getViewerPose()` method will throw an `InvalidState` error. (The viewer's pose can still be queried by passing the `XRSession`'s `viewerSpace` to `XRFrame.getPose()`.)
+All three events are `XRInputSourceEvent` events. When fired the event's `inputSource` attribute will contain the `XRInputSource` that produced the event. The event's `frame` attribute will contain a valid `XRFrame` that can be used to call `getPose()` at the time the selection event occurred. Calling the frame's `getViewerPose()` method will throw an `InvalidState` error. (The viewer's pose can still be queried by passing an `XRReferenceSpace` of type `viewer` to `XRFrame.getPose()`.)
 
 ### Transient input sources
 Some input sources are only be added to the list of input sources while an action is occurring. For example, those with an `targetRayMode` of 'screen' or those with `targetRayMode` of 'gaze' which are triggered by a voice command. In these cases, `XRInputSource` is only present in the array returned by `getInputSources()` during the lifetime of the action. In this circumstance, the order of events is as follows:
diff --git a/spatial-tracking-explainer.md b/spatial-tracking-explainer.md

Original file line number	Diff line number	Diff line change
`@@ -89,7 +89,7 @@ function onSessionStarted(session) {`
`89`	`89`	`}`
`90`	`90`	```
`91`	`91`
`92`		-All three events are `XRInputSourceEvent` events. When fired the event's `inputSource` attribute will contain the `XRInputSource` that produced the event. The event's `frame` attribute will contain a valid `XRFrame` that can be used to call `getPose()` at the time the selection event occurred. Calling the frame's `getViewerPose()` method will throw an `InvalidState` error. (The viewer's pose can still be queried by passing the `XRSession`'s `viewerSpace` to `XRFrame.getPose()`.)
	`92`	+All three events are `XRInputSourceEvent` events. When fired the event's `inputSource` attribute will contain the `XRInputSource` that produced the event. The event's `frame` attribute will contain a valid `XRFrame` that can be used to call `getPose()` at the time the selection event occurred. Calling the frame's `getViewerPose()` method will throw an `InvalidState` error. (The viewer's pose can still be queried by passing an `XRReferenceSpace` of type `viewer` to `XRFrame.getPose()`.)
`93`	`93`
`94`	`94`	`### Transient input sources`
`95`	`95`	Some input sources are only be added to the list of input sources while an action is occurring. For example, those with an `targetRayMode` of 'screen' or those with `targetRayMode` of 'gaze' which are triggered by a voice command. In these cases, `XRInputSource` is only present in the array returned by `getInputSources()` during the lifetime of the action. In this circumstance, the order of events is as follows: