[x3d-public] layering component on the web, multiple scenes

[Andreas Plesch]

Since it may be beneficial to move the x3d standard closer to other web
technologies, I would like to bring up the layering component.

x3dom does not support the layering component (LayerSet, Layer, Viewport
nodes) because you would use web browser controlled CSS positioning of
multiple x3d scenes for the same effect. You would use an enclosing <div>
element (the "rendering surface") and put multiple x3d scene (<x3d> tags)
within it, each with independent content and navigation. Then using CSS
styles it is possible to define size and position of each x3d scene within
the <div> on the web page. The web browser then takes care of compositing
the scene renderings taking into account overlaps, opacity and
such.

This all happens without any additional effort on the x3d browser (x3dom)
side, and has the additional benefit that any other html5 element can be
used in such a composition as well. For example, it is easy to place a
fixed "+" sign in the center for HUD purposes.

For this kind of compatibility with web standards it may be necessary to
include management and compositing of the rendering of multiple x3d scene
graphs into the standard, with the goal of eventually making the layering
component obsolete. For this purpose a superset node <X3DSet> or such may
be useful.

Alternatively, CSS positioning could be explicitly embraced by including
language which defines the <X3D> node (tag?, element?) as being derived
from the <canvas> html5 element when used in web context, eg. on a html5
page, and as such inheriting all canvas CSS properties. This option would
make support for compositing of multiple x3d scenes only applicable in a
web browser case where it would be automatically provided.

-Andreas





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