[x3d-public] Sphere subdivision in to X3DV4 standard

[John Carlson]

I believe there are now "tesselation" or "geometry" shaders now. Do the
browsers support them?

Thanks,

John

On Sun, May 31, 2020 at 10:54 AM Don Brutzman <brutzman at nps.edu> wrote:

> 1, Well said Joe, also thanks to John and Mufti for sharing.
>
> Following that sense of things, I refined the warnings/hints for geometry
> fields in X3D Tooltips.  For example:
>
> ==================================
> * X3D 4.0 Tooltips, Sphere, radius
>    https://www.web3d.org/x3d/content/X3dTooltips.html#Sphere.radius
>
> [radius accessType initializeOnly, type SFFloat CDATA "1"] (0,+∞)
>
> Size in meters.
>
> Warning: simple-geometry dimensions are initializeOnly and cannot be
> changed after initial creation, avoiding the need for potentially expensive
> tessellation at run time.
>
> Hint: for size animation, modify the scale of a parent/ancestor Transform
> node instead.
> ==================================
>
> Questions/improvements/suggestions always welcome.  In some sense this
> file is a kind of context-sensitive FAQ for X3D scene graph.
>
> ----
>
> 2. Meanwhile, there is a relevant Mantis issue pending for X3D 4.0:
>
> * Mantis 1280: Add quality parameter for Geometry3D primitives
>    https://www.web3d.org/member-only/mantis/view.php?id=1280
>
> PDF attached for those without direct access.
>
> Previous thread:
>
> * [x3d-public] Add quality parameter to Geometry3D primitives
>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-February/011748.html
>
> Defining something like "subdivision" field as mentioned there does not
> pass common-sense test.  Any mechanism must be sensible to new authors,
> since primitive nodes are typically what they learn first.
>
> Of note is that browsers are welcome to substitute any geometry they wish
> at run time, including parametric surfaces (as long as geometric results
> are a Sphere with correct radius, for example).
>
> Suggested approach, if included:
> ================================
> [initializeOnly] SFString primitiveQuality "MEDIUM" ["LOW", "MEDIUM",
> "HIGH"]
>
> The /primitiveQuality/ field is an authoring hint regarding tessellation
> resolution expected for this geometry.  Browser implementations may vary.
> ================================
>
> All feedback welcome.  Will put this on next Friday's agenda for X3D
> Working Group resolution, either reject or accept with modifications.
>
>
> On 5/30/2020 7:33 PM, Joseph D Williams wrote:
> >   * … during models lifetime
> >
> > So much is true, please notice the access type of the field.
> >
> > If it is initialize only, then it is set when the node is initialized or
> replaced.
> >
> > This has been used as a clue that the browser has to completely redraw
> the node if the field is changed.
> >
> > Of course the sphere’s shape can be altered by xyz scaling in the parent
> transform so you can change the shape to most anything without a hole but
> not the initialized radius in parent space or the number of points in the
> shape without redrawing it.
> >
> > Thanks,
> >
> > Joe
> >
> > *From: *John Carlson <mailto:yottzumm at gmail.com>
> > *Sent: *Saturday, May 30, 2020 3:47 PM
> > *To: *J. Scheurich <mailto:mufti11 at web.de>
> > *Cc: *X3D Graphics public mailing list <mailto:x3d-public at web3d.org>
> > *Subject: *Re: [x3d-public] Sphere subdivision in to X3DV4 standard
> >
> > Surely you can apply transforms such that the radius changes?
> >
> >> But according to the X3D standards, a sphere may not change its single
> >> parameter (radius)
> >> during models lifetime.
>
>
> 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
> X3D graphics, virtual worlds, navy robotics
> http://faculty.nps.edu/brutzman
>
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