[vtkusers] VTK bindings to Node.js/V8/JavaScript

[Sebastien Jourdain]

I'm catching up, it is only 8:30am here. ;-)

This is awesome! Great work Axel!

This could open other backend to vtkWeb and ParaViewWeb. This is great...

Seb


On Thu, Jan 28, 2016 at 8:13 AM, David E DeMarle <dave.demarle at kitware.com>
wrote:

> Wow!
>
> @David Gobbi and @Sebastien Jourdain did you seen this?
>
> nice work Axel!
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4909
>
> On Thu, Jan 28, 2016 at 4:56 AM, Axel Kittenberger <axkibe at gmail.com>
> wrote:
>
>> Hello,
>>
>> I created a wrapper library generator for VTK to Node.js. If you have all
>> needed packages installed ("node", "vtk6-dev", "qtbase5-dev") running
>>   npm install vtk
>> should do it and compile the pre-generated wrapper classes matching the
>> VTK library found on your system. Currently I included pre-generated
>> wrappers for VTK 6.1, 6.2 and 6.3 (on Linux).
>>
>> The full source code: https://github.com/axkibe/node-vtk
>>
>> Example code creating a cone:
>> --------------------------
>> 'use strict';
>> var vtk, source, mapper, actor, renderer, renderWindow,
>> renderWindowInteractor;
>>
>> vtk = require('vtk');
>>
>> source = new vtk.ConeSource();
>> source.setResolution( 10 );
>>
>> mapper = new vtk.PolyDataMapper();
>>
>> mapper.setInputConnection( source.getOutputPort() );
>>
>> actor = new vtk.Actor();
>> actor.setMapper( mapper );
>>
>> renderer = new vtk.Renderer();
>> renderer.addActor( actor );
>> renderer.setBackground( 0.3, 0.2, 0.1 );
>> renderer.resetCamera();
>>
>> renderWindow = new vtk.RenderWindow();
>> renderWindow.addRenderer( renderer );
>>
>> renderWindowInteractor = new vtk.RenderWindowInteractor();
>> renderWindowInteractor.setRenderWindow( renderWindow );
>> renderWindowInteractor.setInteractorStyle( new
>> vtk.InteractorStyleTrackballCamera() );
>>
>> renderWindow.render();
>>
>> renderWindowInteractor.start();
>> --------------------------
>>
>> I know there is Paraview having a JavaScript interface to interact with
>> on browser side, but this module directly includes VTK on Node.js server
>> side or simply for small rapid development scripts if someone like me just
>> likes JavaScript to prefer this for quick testing instead of other wrappers
>> or using C++ directly.
>>
>> What I did is:
>>
>> * Hijack the VTK wrapping tools build scripts to generate V8 wrapping
>> classes using the "Native Abstractions for Node" (nan) layer. This doesn't
>> build the binary libraries right away but stops after generating the
>> wrapper classes to be copied over the Node.js module build system.
>>
>> * Figure out how to expose hierarchical native data as hierarchical
>> JavaScript objects creating a matching prototype chain. I didn't find
>> example code for this as most nan examples where simply object here <->
>> object there mappings.
>>   var vtk = require('vtk')
>>   var source = new vtk.ConeSource();
>>   console.log( source instanceof vtk.Algorithm, source instanceof
>> vtk.CubeSource );
>> correctly prints out "true false"
>>
>> * Creating overload detection and figure out the correct native overload
>> to call.
>>
>> * Make the wrapping as foolproof as I could think of. At least I don't
>> know how to create a Segfault from JavaScript side, everything wrong doing
>> should raise a JavaScript exception instead.
>>
>> * Lazily initialize JavaScript prototypes only as they are needed. On
>> startup only getters for the VTK object are set, everything else is only
>> initialized when accessed. This improves startup time. After the first
>> start of node with VTK which takes a long time (10 seconds for me) for I
>> suppose the linker doing its stuff, subsequent calls start up the whole
>> thing in 1 second.
>>
>> * Set references for different naming conventions what you prefer.
>> vtk.vtkConeSource (strictly correct and VTK case scheme, but kind of
>> repetitive saying "vtk" twice and violating JavaScript conventions of
>> constructor functions being uppercase) and vtk.ConeSource (shorted and fits
>> the convention of uppercase constructors) point to the same thing. Similar
>> source.SetResolution (strictly correct VTK name) and source.setResolution
>> (JavaScript convention for lowercase non-constructor functions) are the
>> same thing too.
>>
>> What I did not:
>>
>> * I skipped a lot of less used parameter types. Right now wrappers are
>> only created for functions having double, char, char (const) *, int and
>> vtkObject pointers as parameters and return values. Other primitives should
>> be easy to add, I just didn't yet need them.
>> Predefined length arrays as parameters might be a little more work.
>> QObject I didn't look at. Templates as parameters (as Tuples) I don't know
>> how to and I suppose PythonWrapping, which I used as guideline, doesn't
>> either. C++ Classes/Structs not being a child of vtkObjectBase are excluded
>> as vtk-node uses vtkSmartPointers for all its objects and these don't work
>> there.
>>
>> * Create the .so libraries right from within the VTK build.
>>
>> * Create altered WindowInteractor derivates which keep the node event
>> loop running. I looked a little into XWindowRenderInteractor and there it
>> should be very possible to have the X-event loop halt its select() and
>> timer calculations in a separate thread, but hand on any X message via
>> semaphore to be processed in the main thread.
>>
>> * Detect other operating systems than Linux in the "npm install" script
>> and include/exclude the correct wrapper classes.
>>
>> Kind regards,
>>
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