[x3d-public] X3D VR

[Andreas Plesch]

On Wed, Dec 21, 2016 at 6:00 AM, Roy Walmsley <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?
>

I agree it is often constructive to have more specific suggestions to
discuss and iterate, so I will give this a try. In the mean time, it also
useful to collect more diffuse ideas or existing solutions into a central
place like this thread.


> 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.
>

Here is another item for discussion. For VR it is especially necessary to
be thoughtful about performance since high frame rates, high resolution and
the doubled output are all important. Ideally, one would want to traverse
the scene graph only only once per frame and generate right and left render
output in parallel. To enable this approach, it seems it is necessary to
have special VR/stereo nodes or modes so the browser can optimize in this
way. Perhaps LayerSet allows for this kind of parallel rendering of
multiple views of the same scene currently ?

Definitely hoping for a lively discussion,

-Andreas

Thank you for the suggestions,
>
>
>
> All the best,
>
>
>
> Roy
>
>
>
> *From:* x3d-public [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>
> *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
>



-- 
Andreas Plesch
39 Barbara Rd.
Waltham, MA 02453
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