[vtkusers] InteractionProp in Java

[Jim Peterson]

Correction on my last, I can set the ModifiedEvent observer on the actor 
then GetOrientation(), GetScale() and GetPosition() on the actor. It is 
a little noisy, it might be better if I could get an ending interaction 
event.

Hope that helps,
Jim

Ambar C wrote:
> Right - I didn't understand that JNI wouldn't let the members
> propagate, thanks for that.
>
> I'm trying to build a system where the user can move (rotate,
> translate) the shown actor using a mouse, and those changes should
> take place in the actual data itself. To do this I'd need to be able
> to find out the transformations the user is making with the mouse so
> that I can apply them to my data. In C++ the trackballactor's
> InteractionProp member let me get the current orientation and
> position, but I can't find anything in Java that lets me do that. Any
> help would be appreciated.
>
> Best,
> Ambar
>
> On Sat, Nov 13, 2010 at 2:02 PM, Jim Peterson <jimcp at cox.net> wrote:
>   
>> Ambar,
>> In my opinion, you have a solution that worked in C++, extend the function
>> of the class in C++ which makes protected attributes available to your code.
>> You are expecting extending the java wrapper to that C++ class to behave the
>> same. You are correct, the protected variable InteractionProp is not
>> accessible directly from Java because the JCI exposes the get/set functions
>> and other public functions of the class, the fact is no attributes of the
>> C++ classes are available as attributes of the corresponding Java classes.
>> My best understanding of JNI is no attributes of the native classes are
>> available by direct reference, the only access to attributes is via get/set
>> functions, and InteractionProp is protected in vtk and therefore not
>> exposed.
>>
>> It could be you have an argument for providing a getInteractionProperty from
>> the interactionStyle classes, but I would say it needs to be justified by
>> something other than "it is not accessible".
>>
>> The bottom line is you apparently have a C++ class that implements what you
>> want. If you want to code an interface change in Java you need to start from
>> what you want and chose a solution that is available, like an addObserver
>> callback or an interaction using display of vtk from Java.
>>
>> Maybe this discussion would be more productive if you describe what you want
>> to do in terms of changing the interaction behavior and not how you think
>> you should be able to do it.
>>
>> Hope that helps,
>> Jim
>>
>> Ambar C wrote:
>>     
>>> Hello,
>>>
>>> I understand the way JNI works in VTK, but the member that I'm having
>>> trouble accessing isn't something that I've overloaded any C++ class
>>> with. I'm trying to be able to access the InteractionProp member of
>>> the vtkInteractorStyleTrackballActor, which is a protected member
>>> object of the class. My observation so far is that this member doesn't
>>> seem to be recognized in the Java wrapped implementation. I'm not sure
>>> how JNI would tie into this lack of propagation, but do correct me if
>>> I'm wrong.
>>>
>>> Cheers,
>>> Ambar
>>>
>>> On Sat, Nov 13, 2010 at 10:37 AM, Jim Peterson <jimcp at cox.net> wrote:
>>>
>>>       
>>>> Ambar,
>>>> The set of vtk classes available in Java are not actually java classes,
>>>> they
>>>> are interfaces with the C++ vtk classes implemented in the vtk shared
>>>> libraries. The Java terminology is the classes are implemented via the
>>>> Java
>>>> Native Interface (JNI). As such, you cannot extend vtk classes in Java to
>>>> add functionality as you might in C++. The vtk C++ logic is unaware of
>>>> the
>>>> Java extensions.
>>>> You have at least three choices are:
>>>> 1. Add your modified C++ class to vtk so that it is included in one of
>>>> the
>>>> vtk shared libraries and wrapped by the Java interface and available to
>>>> your
>>>> Java program.
>>>> 2. Use the mouse move or other interaction callbacks in your java code to
>>>> gain control and interact with your vtk model.
>>>> 3. Use the relatively undocumented vtkRenderWindowPanel class from  Java
>>>> so
>>>> that you can use Java UI events to interact with the vtk object.
>>>>
>>>> I am not exactly sure what your eventual goal is other that the
>>>> interaction
>>>> modifications, but some examples of the java addObserver callbacks and
>>>> Swing
>>>> panel implementation are available from here:
>>>> http://www.vtk.org/Wiki/VTK/Examples/Java
>>>>
>>>> Hope that helps,
>>>> Jim
>>>>
>>>> Ambar C wrote:
>>>>
>>>>         
>>>>> Hi Jim,
>>>>>
>>>>> Could you be more specific? What would I need to do to be able to grab
>>>>> the mouse driven value changes in orientation and position in Java? I
>>>>> don't understand how I'd be able to replace the interaction prop's
>>>>> functionality. Thanks for the help.
>>>>>
>>>>> Best,
>>>>> Ambar
>>>>>
>>>>> On Tue, Nov 9, 2010 at 4:04 AM, Jim Peterson <jimcp at cox.net> wrote:
>>>>>
>>>>>
>>>>>           
>>>>>> Ambar C wrote:
>>>>>>
>>>>>>
>>>>>>             
>>>>>>> Hello,
>>>>>>>
>>>>>>> I'm working on modifying an vtkInteractorStyleTrackballActor to have
>>>>>>> my own custom class, and am trying to access it's InteractionProp
>>>>>>> member but it doesn't seem to be coming through. The equivalent code
>>>>>>> works in C++, but something along the lines of
>>>>>>>
>>>>>>> public modifiedClass extends vtkInteractorStyleTrackballActor
>>>>>>> {
>>>>>>>   .....
>>>>>>>   this.InteractionProp. //Doesn't recognize the member.
>>>>>>>
>>>>>>> }
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>               
>>>>>> Ambar,
>>>>>> I think this is not a valid construct for classes that are used for JNI
>>>>>> interfaces. Yes, Java compiles it, but no, there is no runtime
>>>>>> inheritance
>>>>>> to the c++ classes.  The pure java way to modify interaction behavior
>>>>>> is
>>>>>> to
>>>>>> use the interaction observers. If you want to use your C++ code you
>>>>>> would
>>>>>> need to add it to the vtk source tree and rebuild both vtk and the java
>>>>>> wrappers, The new class can be wrapped and accessible to Java in that
>>>>>> way.
>>>>>>
>>>>>> If you need to address this completely in Java, maybe it would be
>>>>>> better
>>>>>> to
>>>>>> identify your desired modification to the interaction rather than the
>>>>>> solution first.
>>>>>>
>>>>>> Hope that helps,
>>>>>> Jim
>>>>>>
>>>>>>
>>>>>>
>>>>>>             
>>>>>           
>>>>         
>>>       
>>     
>
>