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

[David E DeMarle]

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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