protected void writeGlExportsToLibGL() throws P5ExportException {
    
    // make sure we have libe/opengl dir
    if (libDir == null)
      libDir = new File(System.getProperty("user.dir"), "lib");
    if (!libDir.exists()) 
      throw new P5ExportException("No lib dir found at: "+libDir.getPath());
    if (libGl == null)
      libGl = new File(libDir, "opengl");   
    if (!libGl.exists()) libGl.mkdirs();
    
    // Write the GL native jars if we need them...
    try {
      P5ExportUtils.writeJarResourcesAsFiles(getClass(), P5ExportBuilder.P5_EXPORTS_GL_JAR, libGl);
    } catch (Exception e) {
      throw new P5ExportException(e);
    }
  }