[x3d-public] Node.js for X3DJSAIL. Beginnings in X3DJSONLD. typecast issues

[John Carlson]

Was able to solve with newFloat method, a very verbose way to specify a
float.

John

On Sat, Oct 20, 2018 at 1:00 AM Brutzman, Donald (Don) (CIV) <
brutzman at nps.edu> wrote:

> Hi John.  Thanks for this interesting example.
>
> As the error logs indicate, accessor methods using double types are not
> provided for X3D fields having SFFloat/MFFloat types in the current
> X3DJSAIL implementation.  Javadoc confirmation:
>
>
> http://www.web3d.org/specifications/java/javadoc/org/web3d/x3d/jsail/Shape/MaterialObject.html#setAmbientIntensity-float-
>
> http://www.web3d.org/specifications/java/javadoc/org/web3d/x3d/jsail/Shape/MaterialObject.html#setAmbientIntensity-org.web3d.x3d.jsail.fields.SFFloatObject-
>
> Java compilation issues warnings when source code tries putting a double
> into a float, so that the programmer knows a reduction in precision is
> occurring.
>
> In a source program, a programmer can address this and silence warnings by
> deliberate casting, i.e. saying something like
>
>         myMaterialObject.setAmbientIntensity((float) 0.123456789d);
>
> Two general solution approaches would seem to present themselves:
>
> a. keep X3DJSAIL accessor methods strict so that authors (or conversion
> tools) must explicitly handle type-casting in a deliberate fasion.
> b. make X3DJSAIL overloaded with various types so that programmers don't
> know  and aren't notified when downcasting and loss of precision occurs.
>
> Given that X3D presentation might have really strict usage requirements
> (for example CAD parts fitting together) the current X3DJSAILdesign is to
> stay strict throughout.  Downcasting and type conversion is certainly
> possible but must be deliberately accomplished by authors.
>
> Yes agreed that JavaScript and JSON are always double precision.  This is
> unavoidably allowed by X3D ECMAScript language binding and X3D JSON
> encoding regardless of X3D Architecture and X3DUOM requirements.
>
> It will be interesting to see if you can adapt/wrap things as indicated.
> We will likely to again face the exact same issue in a Python binding,
> since the Python language puts a high premium on completely hiding
> typecasting from the programmer.
>
> A future design option might be to provide such overloading, perhaps even
> selectively deployed as x3djsail-strict and x3djsail lenient builds.
>
> As with JSON, we don't particularly want JavaScript programmers to have to
> worry about this all the time.
>
> Good luck!
>
> On 10/17/2018 8:12 PM, John Carlson wrote:
> > I am beginning to port X3DJSAIL to Node.js, using the java npm module to
> interface node.js to java.  I have seen a tiny bit of success, but am
> beginning to see hard problems that can might be solved by modifying
> X3DJSAIL, perhaps significantly, or undesirably, due to JavaScript or node
> limitations, not found in Nashorn.
> >
> > [...]
> >
> > Error: Could not find method "setAmbientIntensity(java.lang.Double)" on
> class "class org.web3d.x3d.jsail.Shape.MaterialObject". Possible matches:
> >
> >    public org.web3d.x3d.jsail.Shape.MaterialObject
> org.web3d.x3d.jsail.Shape.MaterialObject.setAmbientIntensity(org.web3d.x3d.jsail.fields.SFFloatObject)
> >
> >    public org.web3d.x3d.sai.Shape.Material
> org.web3d.x3d.jsail.Shape.MaterialObject.setAmbientIntensity(float)
> >
> >    public org.web3d.x3d.jsail.Shape.MaterialObject
> org.web3d.x3d.jsail.Shape.MaterialObject.setAmbientIntensity(float)
> >
> >      at Object.<anonymous>
> (C:\Users\coderextreme\X3DJSONLD\src\main\node\net\coderextreme\data\flipp.js:27:75)
> >
> >      at Module._compile (module.js:652:30)
> >      at Object.Module._extensions..js (module.js:663:10)
> >      at Module.load (module.js:565:32)
> >      at Function.Module._load (module.js:497:3)
> >      at Function.Module.runMain (module.js:693:10)
> >      at bootstrap_node.js:609:3
> >
> > Note that all JavaScript numbers are doubles I believe.  I will have to
> investigate the npm module to see if it supports floats.
> >
> > Indeed it does, the syntax is:
> >
> > |var f = java.newFloat(3.14);|
> >
> > Back to work.
> >
> > This should probably be mentioned in any JavaScript API which uses
> X3DJSAIL.
> >
> > John
>
>
> 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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