[x3d-public] LOD first level_changed event

[Andreas Plesch]

On Fri, Apr 6, 2018 at 9:21 PM, Andreas Plesch <andreasplesch at gmail.com> wrote:
> https://x3d-lodlevel-test.glitch.me/LODwithDifferentShapes.x3d
>
> tests if an initial level_changed event is generated. If it is,
> 'Choice 0' is displayed on front of the red cube, at first display. If
> not, no text is displayed.
>
> x marks the browser which show the text:
>
> x3dom: x
> Instant Player: x
> H3DViewer: x
> View3dScene: x
>
> Octaga
> BS Contact
>
> FreeWrl
> X-ITE
>
>
> FreeWrl and X-ITE do not show text even after initialisation and
> changing LOD levels. So they may not support level_changed.
>
> Apparently there are differences in spec. interpretation.

So this suggests that there is a need to tighten the spec. language. I
would be in favor of generating the first time event.

The relevant sentence is:

 ' When L(d) is activated for display,
the LOD node generates a level_changed event with value i where the
value of i identifies which value of L was activated for display.'

Would add 'including the first time' suffice ?

' When L(d) is activated for display including the first time,
the LOD node generates a level_changed event with value i where the
value of i identifies which value of L was activated for display.'

If there is no immediate objection I can add a standard comment via web3d.org .

-Andreas
>
>
>
> On Fri, Apr 6, 2018 at 8:11 PM, Andreas Plesch <andreasplesch at gmail.com> wrote:
>> LOD has an outputOnly level_changed field which indicates the level
>> index of a child when it is activated.
>>
>> Should the level_changed event be generated the very first time the
>> LOD activates any of its children ?
>>
>> It looks like it should and the spec. does not treat the
>> initialization as a special case: When L(d) is activated for display,
>> the LOD node generates a level_changed event with value i where the
>> value of i identifies which value of L was activated for display.
>>
>> On the other hand, the first display may not be considered a change
>> from a previous display. But it is a change from no display, and
>> generally logic using the event should work for the initial case as
>> well.
>>
>> So I think the answer is yes but thought it is worth raising the
>> question before the field is added to x3dom.
>>
>> Perhaps it is time to put together a simple test using an existing LOD
>> example by adding a route from level_changed to a switch node to see
>> if it gets an initial value.
>>
>> Any feedback welcome,
>>
>> -Andreas
>>
>> --
>> Andreas Plesch
>> Waltham, MA 02453
>
>
>
> --
> Andreas Plesch
> Waltham, MA 02453



-- 
Andreas Plesch
Waltham, MA 02453