[x3d-public] metadata for ProtoInstance

Don Brutzman brutzman at nps.edu
Sat Jun 6 11:05:03 PDT 2020 

[possible Web3D 2020 participant gift: skateboard bumperstickers that say "X3D Prototypes Are Not A Crime"]

8)

On 6/5/2020 12:45 PM, Andreas Plesch wrote:
> Indeed,
> 
> https://savage.nps.edu/Savage/Tools/Animation/DoubleClickTouchSensorPrototypeIndex.html
> 
> shows that pattern of allowing metadata for a ProtoInstance. Perhaps
> the exposed metadata field should be populated in the example
> ProtoInstance as well.

Sounds good, thank you.  Excerpt follows, checked in and validated.

     <ProtoDeclare appinfo='DoubleClickTouchSensor functionality activates when user double clicks (or double selects) within maxDelayInterval' name='DoubleClickTouchSensor'>
       <ProtoInterface>
         <field accessType='inputOutput' appinfo='describe the purpose of this sensor' name='description' type='SFString'/>
         <field accessType='initializeOnly' appinfo='seconds' name='maxDelayInterval' type='SFTime' value='0.5'/>
         <field accessType='inputOutput' name='enabled' type='SFBool' value='true'/>
         <field accessType='outputOnly' name='isActive' type='SFBool'/>
         <field accessType='outputOnly' name='isOver' type='SFBool'/>
         <field accessType='outputOnly' appinfo='seconds' name='touchTime' type='SFTime'/>
         <field accessType='outputOnly' name='hitPoint_changed' type='SFVec3f'/>
         <field accessType='outputOnly' name='hitNormal_changed' type='SFVec3f'/>
         <field accessType='outputOnly' name='hitTexCoord_changed' type='SFVec2f'/>
         <field accessType='initializeOnly' name='metadata' type='SFNode' appinfo='can contain one of Metadata nodes'>
           <!-- initialization node (if any) goes here -->
         </field>
         <field accessType='initializeOnly' name='traceEnabled' type='SFBool' value='false'/>
       </ProtoInterface>
...

     <ExternProtoDeclare appinfo='DoubleClickTouchSensor functionality activates when user double clicks (or double selects) within maxDelayInterval' name='DoubleClickTouchSensor' url='"DoubleClickTouchSensorPrototype.x3d#DoubleClickTouchSensor" "../../../Savage/Tools/Animation/DoubleClickTouchSensorPrototype.x3d#DoubleClickTouchSensor" "https://savage.nps.edu/Savage/Tools/Animation/DoubleClickTouchSensorPrototype.x3d#DoubleClickTouchSensor" "DoubleClickTouchSensorPrototype.wrl#DoubleClickTouchSensor" "../../../Savage/Tools/Animation/DoubleClickTouchSensorPrototype.wrl#DoubleClickTouchSensor" "https://savage.nps.edu/Savage/Tools/Animation/DoubleClickTouchSensorPrototype.wrl#DoubleClickTouchSensor"'>
       <field accessType='inputOutput' appinfo='describe the purpose of this sensor' name='description' type='SFString'/>
       <field accessType='initializeOnly' appinfo='seconds' name='maxDelayInterval' type='SFTime'/>
       <field accessType='inputOutput' name='enabled' type='SFBool'/>
       <field accessType='outputOnly' name='isActive' type='SFBool'/>
       <field accessType='outputOnly' name='isOver' type='SFBool'/>
       <field accessType='outputOnly' appinfo='seconds' name='touchTime' type='SFTime'/>
       <field accessType='outputOnly' name='hitPoint_changed' type='SFVec3f'/>
       <field accessType='outputOnly' name='hitNormal_changed' type='SFVec3f'/>
       <field accessType='outputOnly' name='hitTexCoord_changed' type='SFVec2f'/>
       <field accessType='initializeOnly' name='metadata' type='SFNode' appinfo='can contain one of Metadata nodes'>
           <!-- initialization node (if any) goes here -->
       </field>
       <field accessType='initializeOnly' name='traceEnabled' type='SFBool'/>
     </ExternProtoDeclare>
...

       <ProtoInstance DEF='TouchSensorActive' name='DoubleClickTouchSensor'>
         <fieldValue name='description' value='double click to initiate time delay and color change'/>
         <fieldValue name='traceEnabled' value='true'/>
         <fieldValue name='metadata'>
             <MetadataString name="exampleTerm" value='"exampleValue"'/>
         </fieldValue>
       </ProtoInstance>

This design pattern seemed too specialized to add to X3D Tooltips, but I have added an entry with links to

* X3D Scene Authoring Hints, Inline Scenes and Prototype Templates
   https://www.web3d.org/x3d/content/examples/X3dSceneAuthoringHints.html#Inlines

"If an author wants a ProtoInstance node to contain metadata like other X3D nodes, then first add a metadata field to the defining ProtoDeclere. For an example, see DoubleClickTouchSensorPrototype and DoubleClickTouchSensorExample."

> Authors should consider ProtoInstance as a node in the scenegraph.
> Does that indicate that the spec. also should consider ProtoInstance
> more formally as a node, rather than a statement ? The SAI efforts, I
> think, already do that. It would be a node which is dynamically
> defined as it derives its definition from the named Protodeclaration.
> So instead of treating it as something to be replaced/expanded, it
> would be stay in the scenegraph and reference the Protodeclaration.

 From a 'specification parlance' perspective, ProtoDeclare ExternProtoDeclare ProtoInstance (PROTO EXTERNPROTO [someName] ) are statements.

 From a practical perspective, an instantiated ProtoInstance is a node (or node subtree) in the scene graph.

In X3DJSAIL some creativity was needed, class ProtoInstanceObject  indrectly implements X3DChildNode (and thus X3DNode) with the following signature:

	public class ProtoInstanceObject extends X3DConcreteNode implements ProtoInstance

* https://www.web3d.org/specifications/java/javadoc/org/web3d/x3d/jsail/Core/ProtoInstanceObject.html

The specification prose seems pretty thorough about all these ins & outs... no doubt you've seen it.

* X3D Architecture, 4.4.4 Prototype semantics
   https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/concepts.html#PrototypeSemantics

For anybody, questions or potential spec clarifications are always welcome.

> To be honest, I am a bit worried that if Proto's should become
> available for x3dom, there will be unnecessary management of
> expectations, mostly with regards to scripting. So strategically, it
> will be best to first figure out if it is possible to reproduce
> scripted prototype behaviours with dom scripts, and only then release
> more widely.
> 
> -Andreas

Understood, please implement/rollout as you think best.  Each will be a major advance for X3DOM.  Suggest getting prototypes out without scripting is a good incremental achievement; acknowledged that many prototype declarations include scripting for advanced capabilities.

Looking ahead in that direction...

I've always thought that a <Script> within a <Scene> within a root <X3D> ought to be pretty easy to distinguish from a HTML Script.  However I haven't actually tried to do that in any DOM programming.  MIght be an issue if the page is some kinda tag soup (which HTML allows, I think).

If you want to experiment with <X3dScript> as a synonym, that might be an interesting experiment.  If it seems necessary then we could write that up in the forthcoming X3D4 section for X3D-HTML.  Similarly we might consider implications of using <X3DCanvas> (as X_ITE does) when scene graph is external to the HTML page.

We're having fun now... Thanks Andreas!

> On Fri, Jun 5, 2020 at 9:54 AM Don Brutzman <brutzman at nps.edu> wrote:
>>
>> Great question about metadata in a protoinstance... i believe that your deduction is correct and that we have some examples.  here are some:

p.s. it took me a heckuva lot longer (weeks maybe) than the few hours you apparently needed to figure that one out - very impressive!!  8)

>> [1] X3D Example Archives: Savage, Tools, Animation, Flying Text Prototype
>>       https://savage.nps.edu/Savage/Tools/Animation/FlyingTextPrototypeIndex.html
>>
>> [2] X3D Example Archives: Savage, Tools, Animation, Flying Text Example
>>       https://savage.nps.edu/Savage/Tools/Animation/FlyingTextExampleIndex.html
>>
>> <field name='metadata' type='SFNode' accessType='initializeOnly'/>
>>
>> [3] X3D Example Archives: Savage, Tools, Animation, Double Click Touch Sensor Prototype
>>       https://savage.nps.edu/Savage/Tools/Animation/DoubleClickTouchSensorPrototypeIndex.html
>>
>> <field name='metadata' type='SFNode' accessType='initializeOnly'>
>>       <!-- initialization node (if any) goes here -->
>> </field>
>>
>> [4] X3D Example Archives: Savage, Tools, Animation, Double Click Touch Sensor Example
>>       https://savage.nps.edu/Savage/Tools/Animation/DoubleClickTouchSensorExampleIndex.html
>>
>> Authors should definitely consider a ProtoInstance as a node in the scene graph.
>>
>> btw i fixed a small error in x3d.py for serializing out typed values found in field/fieldValue declarations, wrapping str() around the value being written out.  planning to deploy an x3d.py at the end of the weekend, hopefully.
>>
>> Finally, i expend demand for ProtoInstance to shoot way up as people understand it and as X3DOM matches support found in other key implementations (InstantReality, X_ITE, Xj3D, others).  Will be happy for the community to check compliance all around, especially if you and John Carlson et al. are successful in finally bringing it to X3DOM some day.
>>
>> Prototypes are a fundamental part of the "X" in X3D.  Onward we go...
>>
>> On 6/4/2020 3:36 PM, Andreas Plesch wrote:
>>> I realized that the way to add metadata to a protoinstance is expose a
>>> metadata field in the protodeclaration. I think that answers my
>>> question.
>>>
>>> -Andreas
>>>
>>> On Thu, Jun 4, 2020 at 3:31 PM Andreas Plesch <andreasplesch at gmail.com> wrote:
>>>>
>>>> I think a ProtoInstance currently cannot have its own, instance
>>>> specific metadata node since it is a statement rather than a node.
>>>>
>>>> Is that correct ?
>>>>
>>>> If so, it does not seem to be much of an issue since there does not
>>>> seem to be much demand for it. But everything else can have associated
>>>> metadata, so should a ProtoInstance not have this ability as well ?
>>>>
>>>> -Andreas

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

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