[x3d-public] OrthoViewpoint fieldOfView - and display size

[Andreas Plesch]

Hi Don,

On Fri, May 25, 2018 at 8:30 PM, Don Brutzman <brutzman at nps.edu> wrote:
> Succinct response to good analysis:  it seems like we can achieve:
>
> a. a singular consistent 1-tuple definition for fieldOfView field in
> Viewpoint, GeoViewpoint (and likely X3DViewpointNode).

No change may be needed.

> b. a separate additional definition for OrthoViewpoint functionality that
> maximizes consistency with existing fields (i.e. unchanged view direction)
> and maps well to OpenGL/HTML5/SVG.
>
> The Mozilla functions are certainly interesting.  For maximum
> interoperability of scene content, we should be looking most closely at:
>
> c. best consistency forOpenGL/HTML5/SVG specifications themselves, and

The MDN pages link to the SVG spec.:
https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/viewBox
https://www.w3.org/TR/SVG11/coords.html#ViewBoxAttribute
There are helpful figures and a lot of prose.

> d. best ability to X3D authors to control viewing area, either using native
> X3D or hybrid HTML5/X3D.

I can see that it is useful to query the pixel dimensions of the
viewport from inside a X3D scene. But to allow a X3D scene to control
and modify the x3d browser window or element size, or fullscreen mode,
is a more sensitive matter since it shifts control away from the user.
For example, web browser now require a 'user gesture' before allowing
a web page (app) to go fullscreen or display on another screen like a
headset for VR.

For x_ite and x3dom it is already possible/straightforward via hybrid
HTML5/X3D to query and modify the size of the 3d canvas element which
is used as a X3D rendering surface.

> Plus perhaps one more thing:  looking ahead with X3D v4.1 in mind, look at
> how
>
> e. draft WebVR specification addresses aspect ration and screen pixel
> dimensions.

Ok. Let's take a look. My guess is that WebXR only tries to make all
necessary information available to an webgl author and then keeps the
responsibility to render in a satisfactory manner on multiple devices
on the author/app.

-Andreas

-- 
Andreas Plesch
Waltham, MA 02453