[x3d-public] BooleanFilter inputFalse output value true or false ?

[Andreas Plesch]

freewrl also uses inputFalse with a false value but not without a dedicated
comment:

https://sourceforge.net/p/freewrl/git/ci/master/tree/
freex3d/src/lib/scenegraph/Component_EventUtils.c#l45
https://sourceforge.net/p/freewrl/git/ci/master/tree/
freex3d/codegen/VRMLNodes.pm#l2644

-Andreas


On Mon, Sep 4, 2017 at 9:49 AM, Andreas Plesch <andreasplesch at gmail.com>
wrote:

> I agree, inputFalse should produce false since BooleanFilter is designed
> as a pass through filter. It is just a matter of the spec. language being a
> bit too concise.
> 'based on the Boolean value received' mostly refers to which of the
> possible output event should be generated, inputTrue or inputFalse. But the
> phrase is ambiguous with regards to the associated values.
>
> What about
>
> 'When the set_boolean event is received, the BooleanFilter node generates
> two events: either inputTrue with a value of true or inputFalse with a
> value of false, depending on the Boolean value received;...' ?
>
> But since the question was raised, let's explore the design to see if is
> possible to decide which behaviour may be more useful. How may
> BooleanFilter be used ?
> Sensors are probably the main sources of boolean outputs. Filtering a
> sensor output makes it possible to selectively choose separate responses to
> the output. It is a kind of branching. This branching is achieved by having
> either inputTrue or inputFalse events but is independent of their values.
> Considering a 'false' output value as something positive (true) may often
> be appropriate but completely depends on the scene architecture. So I
> follow Don's reasoning that it is best to keep it simple by forwarding the
> input values.
>
> -Andreas
>
>
> On Mon, Sep 4, 2017 at 12:39 AM, Don Brutzman <brutzman at nps.edu> wrote:
>
>> great question, thanks Andreas.  let's explore.
>>
>> On 9/3/2017 8:18 PM, Andreas Plesch wrote:
>>
>>> Looking at BooleanFilter (http://www.web3d.org/document
>>> s/specifications/19775-1/V3.3/Part01/components/utils.html#BooleanFilter)
>>> I could not decide what the boolean output values for the inputTrue and
>>> inputFalse events were.
>>>
>>> The spec. just has:
>>>
>>> 'BooleanFilter node generates two events: either inputTrue or
>>> inputFalse, based on the Boolean value received; ...'
>>>
>>
>> full prose:
>>
>> "BooleanFilter filters Boolean events, allowing for selective routing of
>> TRUE or FALSE values and negation.
>>
>> When the set_boolean event is received, the BooleanFilter node generates
>> two events: either inputTrue or inputFalse, based on the Boolean value
>> received; and inputNegate, which contains the negation of the value
>> received."
>>
>> Especially, the value for inputFalse is difficult to determine. I
>>> actually was leaning towards the value true for inputFalse when the
>>> received value is false since it is then true that the input value was
>>> false.
>>>
>>
>> yes the semantics of the spec phrasing is a bit ambiguous.  we should get
>> more explicit.
>>
>> However, the tooltips here
>>>
>>> http://www.web3d.org/x3d/content/X3dTooltips.html#BooleanFilter
>>>
>>> claim that the inputFalse value should be false instead, passing on the
>>> value of the input.
>>>
>>
>> reviewing now, i think that is correct, since it is closely following the
>> initial spec sentence clause "based on the Boolean value received".
>>
>> of additional note is the figure that was reviewed by a number of people,
>> linked in tooltips:
>>
>>         Hint: X3D Event-Utility Nodes, Field Event Diagrams
>>         http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09-E
>> ventUtilitiesScripting/X3dEventUtilityNodeEventDiagrams.pdf
>>
>> attached is image excerpt showing BooleanFilter inputs/outputs, plus copy
>> of diagram for convenience.
>>
>> Is that really what other x3d browsers do ?
>>>
>>
>> yes it is good to check.  perhaps a more explicit test scene will help
>> also.
>>
>> I think that [inputFalse passing FALSE] is indeed the right approach, for
>> a few reasons:
>>
>> a. the node name BooleanFilter indicates a filtering action, i.e. only
>> passing some things through, rather than changing them
>>
>> b. if an author filters an event stream to detect a FALSE event, it is
>> detected and usable as such, rather than requiring yet-another negation.
>>
>> c. precise logic like this leads to more succinct and less error-prone
>> event chains.
>>
>> Checking cobweb it appears that it rather uses inputFalse=true here:
>>>
>>> https://github.com/create3000/cobweb/blob/master/src/cobweb/
>>> Components/EventUtilities/BooleanFilter.js#L110
>>>
>>
>> good check, we need to make them all consistent.
>>
>> It looks like clarification is needed,
>>>
>>
>> yes, further comment welcome.  once we're clear, let's
>>
>> d. have an explicit test scene,
>> e. have specific spec prose and perhap add the diagrams,
>> f. add an inputFalse Warning to ensure no ambiguity remains.
>>
>> -Andreas
>>>
>>
>> thanks!
>>
>> 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
>>
>
>
>
> --
> Andreas Plesch
> Waltham, MA 02453
>



-- 
Andreas Plesch
Waltham, MA 02453
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20170904/4fd1b200/attachment.html>