[x3d-public] combine light scoping with rotation transform

[Andreas Plesch]

Doug,

thank you for input. Manipulating the direction field would work but does
require more effort. The approach would not apply to the case of enclosing
the light in a GeoLocation node - a Grouping node -  which allows for using
a direction of '0 0 1' as north directed, in the correct orientation
relative to other geospatially registered geometry. Most of the times you
would want the objects illuminated by the directional light to _not_ be
affected by the same GeoLocation parent as the light.
It just seems like a strange situation where there should be obvious
solution but there does not seem to be.

Perhaps light scope would need to be defined more flexibly than the global
field allows. I could see a "scope" field which defaults to 'global' and
otherwise contains the DEF of a group to which the light should be applied.
Would this interfere with some default logic of scene traversal ?

The use case for such scoping may be limited but manipulating a light
direction with a spheresensor, and the GeoLocation case may be a good start.

-Andreas



Today's Topics:
>
>    1. Re: combine light scoping with rotation transform (doug sanden)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 25 Jul 2015 08:05:30 -0600
> From: doug sanden <highaspirations at hotmail.com>
> To: X3D Graphics public mailing list <x3d-public at web3d.org>
> Subject: Re: [x3d-public] combine light scoping with rotation
>         transform
> Message-ID: <BAY181-W50C1E53DC236806912AFEAB6800 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Andreas,
> I suspect you'll need to use the location and direction attributes of the
> lights, rather than a transform wrapper, to keep the light as sibling to
> your geometry while rotating it. You may need to convert an axis-angle
> rotation to a direction vector.
> -Doug
>
> >
> > X3D experts,
> >
> > I got stuck on a what must be a basic issue with light scoping.
> >
> >
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/lighting.html#Scopingoflights
> >
> > I want to use scoping for a directional light, eg. with a global field
> > set to 'false'
> >
> > <Group>
> > <DirectionalLight global='false' ... />
> > <Shape DEF='illuminated_by_directional_light>
> > ...
> > </Shape>
> > </Group>
> >
> > <Group DEF='not_illuminated_by_directional_light'>
> > ..
> > </Group>
> >
> > Would this be the correct hierarchy to use ?
> >
> > Now I also want to enclose the directional light in a transform, in
> > order to control it by a routed rotation from a OrientationSensor. At
> > the same time, I do not want to rotate the illuminated shape.
> >
> > <Group>
> > <Transform DEF='light_Trafo'>
> > <DirectionalLight global='false' ... />
> > </Transform>
> > <Shape DEF='illuminated_by_directional_light>
> > ...
> > </Shape>
> > </Group>
> > <Group DEF='not_illuminated_by_directional_light'>
> >
> > However, now the Shape is outside the scope of the light, and not
> > affected by it.
> >
> > This is where I am stuck. What would be the correct hierarchy to use
> > for this case ?
> >
> > This is rather theoretical for me because I believe the global field is
> > not supported by x3dom at this point:
> >
> > https://github.com/x3dom/x3dom/issues/83
> >
> > -Andreas
>

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