jNavigation is Java jME port for Recast Navigation written in C++. The project has two parts:

  1. jNavigationNative contains Recast Navigation library and C++ wrapper for java

  2. jNavigation is Java project that uses jNavigationNative and is the project that the end user will use

If there is need for updating Recast Navigation from native side, there are two kinds of updating bindings:

  1. only updating methods as the Recast made more efficient or more precise

  2. adding new methods for Recast use

Updating methods

Only updating methods are easy. The requirements needed:

  • C++ compiler

The jNavigationNative that has following folders and files (it has more, but these are the most important for now):

  • Recast

    • Include

    • Source

  • README.md

  • Recast_wrap.cxx - Java - C++ wrapper

Updating the methods is only the matter of putting all headers from Recast Navigation to Include folder, source to Source folders, and then building the project.

As author of this project used the NetBeans 7.4 for building the project, the following instruction is included, if the building from terminal doesn’t work.

  1. Setting parameters for NetBeans compiler

  2. Remove all headers from Header Files

  3. Remove all source files EXCEPT Recast_wrap.cxx from Source Files

  4. Right click on Header files, select Add Existing Item… or Add Existing Items from Folders… and select needed headers

  5. Right click on Source files, select Add Existing Item… or Add Existing Items from Folders… and select needed source files

  6. Build

  7. Add built project to jNavigation project

  8. Build jNavigation project

Adding new methods from native side

This is more complicated process and it includes the all work done in NetBeans mentioned in previous section. After that, there are two ways to add new function:

  • manually adding code to wrapper

  • creating new wrapper with SWIG

Manually adding code to wrapper

Example of method in wrapper:

SWIGEXPORT jint JNICALL Java_com_jme3_ai_navigation_utils_RecastJNI_rcIntArray_1size(JNIEnv *jenv, jclass jcls, jlong jarg1, jobject jarg1_) {
 ...
}

The Recast_wrap.cxx uses SWIG wrapper so for declaring method in wrapper you must first use the keyword SWIGEXPORT then returning type (for more information on returning types see link), then again keyword JNICALL and then as the name of method Java_com_jme3_ai_navigation_utils_RecastJNI_ + name of class + name of method, after that, there goes list of parameters needed for the function (for more information see link). In body of method write how the function should be used.

After adding method to wrapper, compile project and add it to jNavigation. In jNavigation project in class com.jme3.ai.navigation.utils.RecastJNI.java add native method, and after that add in class from which you would like to use this method to call this native method. It seems a little bit more complicated than it should be, but this also for support for updating native side with SWIG.

Creating new wrapper with SWIG

In some temporary folder add all headers. It shouldn’t contain any subfolders.

The following script was used for generating wrapper:

%module Recast
%include "carrays.i"
%array_class(double, DoubleArray);
%array_class(float, FloatArray);
%array_class(int, IntArray);
%array_class(unsigned char, UCharArray);
%array_class(unsigned short, UShortArray);
%array_class(unsigned int, UIntArray);
%array_class(long, LongArray);
%array_class(bool, BooleanArray)

%{
#include "DetourAlloc.h"
#include "DetourAssert.h"
#include "DetourCommon.h"
#include "DetourCrowd.h"
#include "DetourLocalBoundary.h"
#include "DetourMath.h"
#include "DetourNavMesh.h"
#include "DetourNavMeshBuilder.h"
#include "DetourNavMeshQuery.h"
#include "DetourNode.h"
#include "DetourObstacleAvoidance.h"
#include "DetourPathCorridor.h"
#include "DetourPathQueue.h"
#include "DetourProximityGrid.h"
#include "DetourStatus.h"
#include "DetourTileCache.h"
#include "DetourTileCacheBuilder.h"
#include "Recast.h"
#include "RecastAlloc.h"
#include "RecastAssert.h"
%}

/* Let's just grab the original header file here */
%include "DetourAlloc.h"
%include "DetourAssert.h"
%include "DetourCommon.h"
%include "DetourCrowd.h"
%include "DetourLocalBoundary.h"
%include "DetourMath.h"
%include "DetourNavMesh.h"
%include "DetourNavMeshBuilder.h"
%include "DetourNavMeshQuery.h"
%include "DetourNode.h"
%include "DetourObstacleAvoidance.h"
%include "DetourPathCorridor.h"
%include "DetourPathQueue.h"
%include "DetourProximityGrid.h"
%include "DetourStatus.h"
%include "DetourTileCache.h"
%include "DetourTileCacheBuilder.h"
%include "Recast.h"
%include "RecastAlloc.h"
%include "RecastAssert.h"

%pragma(java) jniclasscode=%{
  static {
    System.load("Recast");
  }
%}

If there are more headers at some moment, include them in both places.

  1. Save script as Recast.i into temp folder with rest of the headers

  2. Install SWIG if not already

  3. Open terminal and go to folder where the script is

  4. Execute command swig -c++ -java Recast.i

  5. Now SWIG will generate Java classes and new Recast_wrap.cxx

  6. Recast_wrap.cxx put in jNavigationNative with new headers and source files, as previously mentioned

  7. Build that project

  8. For jNavigation side, put only new methods in RecastJNI, and use where they are being used. For that you can see in Java class that are build with SWIG.

  9. If method uses some explicit SWIG type, try to use some method for converting it into jME type, or similar. You can probably find something in package com.jme3.ai.navigation.utils