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

[Andreas Plesch]

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/brutzma
> n
>



-- 
Andreas Plesch
Waltham, MA 02453
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