[vtkusers] VTK and Java - JNI issue

Tue Aug 21 04:22:47 EDT 2012

Oups, the code I posted is not axacly right, here it is:

JNIEXPORT jlong JNICALL Java_nativePCL_1triangulation
  (JNIEnv * env, jobject obj, jobject polyDataJava)
{

 // Get the pointer on the input polyData object
 vtkSmartPointer<vtkPolyData> inPolyDataSmartPtr = (vtkPolyData*)(vtkJavaGetPointerFromObject(env,polyDataJava));

 if(inPolyDataSmartPtr != NULL) {
    // Triangulate the input vtk point cloud 
    vtkSmartPointer<vtkPolyData> outPolyDataSmartPtr = Triangulation::triangulate(inPolyDataSmartPtr);

    return (jlong)(size_t) outPolyDataSmartPtr.GetPointer();

 } else {
    // No input data was retrieved
    return 0;
 }
 return 0;
}

________________________________

From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On Behalf Of Monnier, Gilles
Sent: mardi 21 août 2012 10:18
To: A A; vtkusers at vtk.org
Subject: Re: [vtkusers] VTK and Java - JNI issue

Hi,

Thanks for the response. Actually, I succeeded to do what I want with the following method :

vtkJavaGetPointerFromObject

This method is defined into vtkJavaUtil.h (exported in vtkCommonJava.dll). So finally my code is the following to perform a quite fast triangulation with PCL :

JNIEXPORT jobject JNICALL Java_nativePCL_1triangulation
  (JNIEnv * env, jobject obj, jobject polyDataJava)
{

 // Get the pointer on the input polyData object
 vtkSmartPointer<vtkPolyData> inPolyDataSmartPtr = (vtkPolyData*)(vtkJavaGetPointerFromObject(env,polyDataJava));

 if(inPolyDataSmartPtr != NULL) {
    // Triangulate the input vtk point cloud 
    vtkSmartPointer<vtkPolyData> outPolyDataSmartPtr = Triangulation::triangulate(inPolyDataSmartPtr);

    vtkPolyData* polydatatest = (vtkPolyData*) out2PolyDataSmartPtr.GetPointer();
    return (jlong)(size_t) outPolyDataSmartPtr.GetPointer();

 } else {
    // No input data was retrieved
    return NULL;
 }
 return NULL;
}

I didn't know about the auto-generating of JNI from vtk, but I think this will produce quite the same result, and I will make use of that next time, so thanks for the tip.

Regards,
Gilles Monnier.

________________________________

From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On Behalf Of A A
Sent: mardi 21 août 2012 04:26
To: vtkusers at vtk.org
Subject: Re: [vtkusers] VTK and Java - JNI issue

Personally, I would try to avoid hand coding JNI glue code myself. Since VTK already provided facilities for auto-generating JNI code, I would make use of that. You can simply create a subclasses of vtkObject which consists of a static function, say, 

void triangulation(vtkPolyData* inputCloud)

In the implementation of this function, you now have a pointer the vtkPolyData object which you instantiated in the java side. You could compile this class with Java wrapping turned on (See the Examples/Build folder in the VTK source for examples) and link in the PCL library, and all the JNI code will be generated for you. At the beginning of the java program, you will need to make sure to load (with the loadLibrary function) the 2 generated shared libaries plus the PCL library.

On Thu, Aug 16, 2012 at 11:06 AM, Monnier, Gilles <Gilles.Monnier at oce.com> wrote:

	Hi,

	I'm currently facing an issue using VTK with java.

	Actually, I'm trying to integrate a C++ library into my software. This library is PCL (Point Cloud Library), which offer some interesting features concerning triangulation and registration. Here is below how my application is designed:

	Kitware already provide the JNI interface for VTK, but PCL does not. What I would like to do is to be able to request PCL to perform a triangulation on the vtkPolyData I instanciated into my java code.

	Therefore, I started to create the PCL JNI interface by creating a simple method on the java side:

	public native int nativePCL_triangulation(vtkPolyData inputCloud);

	Then after having generated the header file, I need to implement the C++ code of the interface:

	#include <vtkPolyData.h>

	JNIEXPORT jint JNICALL nativePCL_triangulation(JNIEnv * env, jobject obj, jobject polyDataJava)

	{

	       //vtkPolyData* vp = dynamic_cast<vtkPolyData*>(polyDataJava);

	       return 0;

	}

	And here is my issue : How can I retrieve the pointer on the polyData I instanciated into my java code? 

	To be clear, I would like to access the C++ object instanciated by VTK from the C++ part of the interface I want to implement (the best would be a stuff like a dynamic_cast as in the comment above...). I have absolutely no idea how to achieve that.

	Thanks much,

	Gilles Monnier

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