[x3d-public] combine light scoping with rotation transform

[doug sanden]

>
> 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 ?

That's interesting, may lead to some ideas, but has a gotcha: the transform stack above the DEF is needed too in order to pose the light

Q. would it work to rotate the parent instead of the light, then counter-rotate the shape sibling so as to nullify the shape being rotated? 
Or would having a transform around the shape cause the light to not find its local geometry in the browser of your choice?
Do you have a sample scene?


>
> 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<mailto:highaspirations at hotmail.com>>
> To: X3D Graphics public mailing list
> <x3d-public at web3d.org<mailto: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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