[x3d-public] X3D VR and viewing - HMD node or mode?
Andreas Plesch
andreasplesch at gmail.com
Tue Jan 10 19:42:53 PST 2017
On Jan 8, 2017 5:45 PM, "Don Brutzman" <brutzman at nps.edu> wrote:
>
> Another option: can we define HMD parameters separately from existing
Viewpoint and NavigationInfo nodes, so that existing scenes (with many many
viewpoints already defined) might be viewable without modification.
Ok, while sofar the node/field proposals were made from a practical
standpoint taking into account existing or feasible implementations, let's
turn it around and see what should ideally be available from a scene
authoring perspective.
Let's imagine there is a browser and it has built-in options to display an
existing scene in a selected HMD taking advantage of stereo immersion and
head tracking/body tracking.
Let's also assume the scene is designed for both desktop and HMD
experience. This is probably harder than it sounds but scenes designed for
WALK mode with a single viewpoint or careful transitions between
viewpoints, on a human scale, should be a good start.
The browser can figure out optimal rendering resolution, and use the HMD
provided projection and view matrixes for navigation relative to the bound
viewpoint.
All this does not seem to need scene specific information (?). This is why
we had previously discussed a browser configuration file or Engine node
above/next to the scene level.
Now, it turns out that currently the easiest way to add such functionality
to the x3dom browser is to preprocess the scene (via 'injection') to use
additional nodes (the RenderedTexture node). When getting out of HMD mode,
these additional nodes can be removed again.
For other browsers (such as cobweb) it may be advantageous to preprocess
the scene in a different way, requiring other, specialized nodes
(Viewfrustum).
This is just one way to add functionality to a x3d browser and currently
the most available one. It is also modular as nodes can be used for other
purposes.
> Perhaps an HMD node, rather than HMD mode? That is, a separate node that
complements NavigationInfo?
> The VRML and X3D specifications have done an excellent job in being
device neutral (as well as quite supportive of most devices) when defining
user viewing and interaction already. It will be good to keep building on
that device independence, which incidentally lets you create large shared
environments where users have multiple diverse devices interacting.
>
> WebVR might provide an excellent first pass for the parameters that might
be needed for HMDs.
WebVR inspired parameters supplied by/provided to a HMD node could be:
isPresenting: SFBool, currently in use, scene may want to adapt to
immersion experience in some way
Stage: some HMDs have a certain, limited area in which a user can be
tracked and be expected to stay inside. This could be useful information
for a scene. Includes size, location.
Enabled: a scene may want to strictly disable display on a HMD
DeviceID: a scene may want to know a name for the device to reflect
Capabilities: resolution: a scene may want to adapt (hi res textures)
resetPose: make current location/orientation the reference.
>
> Presumably most of fields are metadata for devices to use, which is in
keeping with scenes that can be utilized by many devices.
Hmm, as evidenced above, I tend to think about the reverse, eg. fields
which can be utilized by scenes. So I am probably missing something.
> So if we can agree on parameters then a simple MetadataSet node (or
prototype) for HMD might be sufficient to start performing some
experimentation in developmental versions of players.
>
> Wondering if such metadata is oriented towards several categories at once:
(a) device specific,
all above
(b) scene specific,
I cannot think of anything, eg. imagine how a scene could modify the
behaviour of a HMD. At this point HMDs only have a single mode. In the
future, a HMD may switch between VR, AR, MR and a scene request an expected
mode ?
If we start to also consider controllers, this might be the place where a
scene configures usage of controller buttons and axes.
and (c) user specific (which can also be saved as preferences).
lastPose: pose before exiting HMD mode
resumePose: return to last pose upon entering
...
I am still unsure if I grasped the idea behind using a MetadataSet node as
a conduit between scene and HMD.
Andreas
This might help re-use and portability.
>
>
> On 1/8/2017 12:40 PM, Andreas Plesch wrote:
>>
>> Yves,
>>
>> thanks for your input. While seeing a Viewfrustum node as a
generalization is convincing, there is a practical difference in how it
would be used. Rather than specifying an initial viewpoint from which user
navigation starts/is relative to, the matrices would be used directly for
navigation. Not sure what the implications of this difference are.
>>
>> Another option is to define another navigation mode, 'HMD', which would
take HMD output (the matrixes) and apply it to the current viewpoint. If
the viewpoint is a stereo viewpoint left and right matrixes would be
supplied. Additional navigation from controllers would still need to be
possible. What device 'HMD' refers to could be defined by a new
NavigationInfo field 'hmd' MFString = "''AUTO' 'VIVE' ... " in case of
multiple connected devices.
>>
>> Andreas
>>
>> On Jan 8, 2017 11:38 AM, "Yves Piguet" <yves.piguet at gmail.com <mailto:
yves.piguet at gmail.com>> wrote:
>>>
>>>
>>> I'd also prefer a new node. Another reason is the existence of
OrthoViewpoint: a viewpoint where you specify an arbitrary projection
matrix is a generalization of both Viewpoint and OrthoViewpoint, so it
should logically be a sibling which also implements the X3DViewpointNode
abstract node. Now an extension for stereoscopic views, where you still
have a single viewer position which defines viewer-related sensor events,
LOD, Billboard etc. and a single node traversal for rendering with two
projection matrices, seems fine.
>>>
>>> Yves
>>>
>>>
>>> > On 8 Jan 2017, at 15:29, Andreas Plesch <andreasplesch at gmail.com
<mailto:andreasplesch at gmail.com>> wrote:
>>> >
>>> > > Date: Sat, 7 Jan 2017 21:04:42 +0100
>>> > > From: Holger Seelig <holger.seelig at yahoo.de <mailto:
holger.seelig at yahoo.de>>
>>> > > To: x3d-public at web3d.org <mailto:x3d-public at web3d.org>
>>> > > Subject: Re: [x3d-public] X3D VR
>>> > >
>>> > >
>>> > > I think instead of defining a new field to the existing viewpoints,
it
>>> > > should be considered that for that purpose and new viewpoint node
could
>>> > > be appropriate. A node called something like ?MatrixViewpoint?. This
>>> > > node could have two fields matrix and projectionMatrix. The matrix
field
>>> > > would store the transformation matrix with orientation and position
>>> > > values. The projectionMatrix field would store the projection
matrix.
>>> > > This viewpoint would be an all purpose viewpoint. The main idea is
if
>>> > > one is able to define an ?viewMatrix? field as Andreas proposes he
is
>>> > > able to handle a node like MatrixViewpoint with its matrix fields.
>>> > > Defining a new node has the advantages to left the existing
viewpoints
>>> > > untouched and to handle this behavior in a new node.
>>> > >
>>> > > Holger
>>> >
>>> > It turns out that x3dom and InstantReality have such a node, called
Viewfrustum:
>>> >
>>> > https://doc.x3dom.org/author/Navigation/Viewfrustum.html
>>> >
>>> > So this is a pretty strong argument for a new node instead of new
fields.
>>> >
>>> > New fields have the advantage that they should make it easier to
adapt existing scenes. I think default values could be such that they
guarantee full backward compatibility.
>>> >
>>> > I will try to use Viewfrustum with the x3dom classroom example to
gain some experience.
>>> >
>>> > Andreas
>>> >
>>> > >
>>> > > Am 07.01.2017 um 18:07 schrieb Andreas Plesch:
>>> > > > Hi,
>>> > > >
>>> > > > back from the holiday season, here are proposals for new fields
for
>>> > > > Viewpoint.
>>> > > >
>>> > > > I do not have an x3dom implementation but the idea is to add two
>>> > > > Matrix4d fields:
>>> > > >
>>> > > > projectionMatrix :
>>> > > >
>>> > > > default: NULL
>>> > > >
>>> > > > purpose: allow control of the view projection from 3d to 2d by
such a
>>> > > > matrix from sources such HMD drivers. The projection matrix
controls fov
>>> > > >
>>> > > > The projectionMatrix should be used as is by the browser if not
NULL. If
>>> > > > NULL, a projection matrix shall be contructed from viewpoint
fields.
>>> > > >
>>> > > >
>>> > > > viewMatrix:
>>> > > >
>>> > > > default: unit matrix
>>> > > >
>>> > > > purpose: allow control of the viewer orientation and location by
such a
>>> > > > matrix from sources such as HMD drivers.
>>> > > >
>>> > > > The viewMatrix V shall be combined with the matrix M derived from
the
>>> > > > location/ orientation fields by M * V for rendering use.
>>> > > >
>>> > > > This means that if V is used in a scene exclusively the location
fields
>>> > > > needs to be reset to 0 0 0 from its default by the scene.
>>> > > >
>>> > > > Typical use would be as sinks of routes from (new)
ProjectionSensor or
>>> > > > VRDevice node fields.
>>> > > >
>>> > > > A VRDevice delivers both matrixes for each eye. A scene can then
set up
>>> > > > a viewpoint for each eye, and use Layers to show them side by
side.
>>> > > >
>>> > > > In terms of efficiency, this would seem to require repeated
traversals
>>> > > > of the scene unless both Layers can be recognized to show the
same scene
>>> > > > content.
>>> > > >
>>> > > > A more convenient and integrated alternative would be to
introduce a
>>> > > > stereo SFBool field and have left and right variants of the matrix
>>> > > > fields ( and perhaps also left and right variants of the location,
>>> > > > orientation, fov, zfar, znear fields).
>>> > > >
>>> > > > stereo = false would ignore all left and right fields.
>>> > > > stereo = true would use the left/right fields and render them
side by side.
>>> > > >
>>> > > > Since in this case there is a guaranty that views for each eye
use the
>>> > > > same scene content, only one traversal should be needed to render
both eyes.
>>> > > >
>>> > > > The idea would be switching mono to stereo and back only requires
>>> > > > toggling the stereo field. Navigation may have a similar switch
to and
>>> > > > from mouse/keyboard modes ?
>>> > > >
>>> > > > Implementation in x3dom of viewMatrix and projectionMatrix may be
rather
>>> > > > straightforward. I do not see large obstacles (famous last words
...).
>>> > > > Implementation in cobweb of viewMatrix and projectionMatrix may
be also
>>> > > > straightforward but I am less sure.
>>> > > >
>>> > > > Without layers in x3dom then one could put two scene side by side
on the
>>> > > > web page, use external js to feed the matrix fields, and then
also use
>>> > > > external js to grab the frames from both scene canvases, combine
them
>>> > > > into a single frame on another canvas, and use that finally as a
source
>>> > > > for the HMD display. (This sounds slow).
>>> > > > In cobweb, it should not be hard to set up a scene with a layer
for each
>>> > > > eye.
>>> > > >
>>> > > > Implementation of stereo, left and rightView/ProjectionMatrix in
x3dom
>>> > > > is harder since it needs changes to the rendering code which is a
bit
>>> > > > unstructured. The first approach would be for stereo=true to go
through
>>> > > > the rendering twice with the rendering surfaces appropriately set
somehow.
>>> > > >
>>> > > > -Andreas
>>> > > >
>>> > > > On Dec 21, 2016 6:00 AM, "Roy Walmsley" <roy.walmsley at ntlworld.com
<mailto:roy.walmsley at ntlworld.com>
>>> > > > <mailto:roy.walmsley at ntlworld.com <mailto:
roy.walmsley at ntlworld.com>>> wrote:
>>> > > >
>>> > > > Hi Andreas,____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > That?s great to see what you have been doing here. Would you
like
>>> > > > to take your node suggestions one step further and propose the
>>> > > > fields that might be specified for each node?____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > What we could do then is, in the new year, is to host an open
>>> > > > discussion on WebVR and X3D. Contributions from any other
readers
>>> > > > are welcome, and could lead to a lively discussion on this
topic.____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > Thank you for the suggestions,____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > All the best,____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > Roy____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > *From:*x3d-public [mailto:x3d-public-bounces at web3d.org
<mailto:x3d-public-bounces at web3d.org>
>>> > > > <mailto:x3d-public-bounces at web3d.org <mailto:
x3d-public-bounces at web3d.org>>] *On Behalf Of *Andreas Plesch
>>> > > > *Sent:* 21 December 2016 05:51
>>> > > > *To:* X3D Graphics public mailing list <x3d-public at web3d.org
<mailto:x3d-public at web3d.org>
>>> > > > <mailto:x3d-public at web3d.org <mailto:x3d-public at web3d.org>>>
>>> > > > *Subject:* [x3d-public] X3D VR____
>>> > > >
>>> > > > __ __
>>> > > >
>>> > > > Hi____
>>> > > >
>>> > > > Working with x3dom and WebVR I am exploring what additions to
X3D
>>> > > > would be necessary or useful to effectively use current VR
hardware
>>> > > > such as the Rift, Vive, Gear, or Cardboard.____
>>> > > >
>>> > > > The proposed RenderedTexture node is currently used in x3dom
with
>>> > > > special stereo modes to generate left and right views from a
single
>>> > > > viewpoint in a single GL context.____
>>> > > >
>>> > > > A Layer for each left and right view could also be used with
two
>>> > > > coordinated but separate viewpoints. This would be Cobweb's
pattern.____
>>> > > >
>>> > > > Since the HMD and its own runtime know best the internal
optical
>>> > > > characteristics of the display, the preferred interface at
least in
>>> > > > WebVR are view and projection matrixes directly usable by
consumers
>>> > > > for 3d graphics generation, and not position, orientation and
fov.
>>> > > > This leads to a new requirement for X3D to accept these raw
matrixes
>>> > > > as input.____
>>> > > >
>>> > > > Since x3dom uses RenderedTexture for VR, I added there
additional
>>> > > > special stereo modes which directly receive these matrixes
from the
>>> > > > HMD to be used for rendering at each frame. This in effect
>>> > > > accomplishes a first, head and body based, level of
navigation. In
>>> > > > my first tests (on github) it works well and should be robust
across
>>> > > > devices. This approach does require some standard API to the
HMD
>>> > > > such as WebVR.____
>>> > > >
>>> > > > Another possibility is to add view and projection matrix
fields
>>> > > > input fields to viewpoints which can be continually updated.
One
>>> > > > could convolve the view matrix with position/orientation
fields, or
>>> > > > optionally completely ignore them.____
>>> > > >
>>> > > > One then could use external SAI to keep updating or perhaps
>>> > > > introduce an environment ProjectionSensor. It would relay
these
>>> > > > matrix events from an HMD runtime to then be routed to the
>>> > > > viewpoints.____
>>> > > >
>>> > > > A second level of navigation is accomplished with handheld
>>> > > > controllers. Until some standard gestures evolve, it will be
>>> > > > necessary to expect custom per scene navigation. X3d should
have a
>>> > > > way to sense buttons and axes velocities of such controllers
so
>>> > > > these are then available to manipulate the view in some way.
>>> > > > InstantReality has a general IOSensor to that effect. On the
web the
>>> > > > GamePad API is a standard which would need to be used.____
>>> > > >
>>> > > > Summary: RenderedTexture with stereo modes, matrix fields for
>>> > > > viewpoints, a ProjectionSensor, and a ControllerSensor would
all be
>>> > > > candidates for x3d VR support.____
>>> > > >
>>> > > > Thanks for reading, any thoughts welcome,____
>>> > > >
>>> > > > Andreas ____
>>> > > >
>>> > > >
>>> > > >
>>> > > >
>>> > > > _______________________________________________
>>> > > > x3d-public mailing list
>>> > > > x3d-public at web3d.org <mailto:x3d-public at web3d.org>
>>> > > > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>> > > >
>>> > >
>>> > >
>>> > > --
>>> > > Holger Seelig
>>> > > Mediengestalter Digital ? Digital Media Designer
>>> > >
>>> > > Scheffelstra?e 31a
>>> > > 04277 Leipzig
>>> > > Germany
>>> > >
>>> > > Cellular: +49 1577 147 26 11 <+49%201577%201472611>
>>> > > E-Mail: holger.seelig at create3000.de <mailto:
holger.seelig at create3000.de>
>>> > > Web: http://titania.create3000.de
>>> > >
>>> > > Future to the fantasy ? ?
>>> > >
>>> > >
>>> > >
>>> > > ------------------------------
>>> > >
>>> > > Subject: Digest Footer
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>>> > >
>>> > >
>>> > > ------------------------------
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>>
>>
>>
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>>
>
>
> all the best, Don
> --
> Don Brutzman Naval Postgraduate School, Code USW/Br
brutzman at nps.edu
> Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
+1.831.656.2149 <(831)%20656-2149>
> X3D graphics, virtual worlds, navy robotics
http://faculty.nps.edu/brutzman
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